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Properties of native and blended oil palm starch with nano-silicon dioxide as binder for particleboard
Journal Pre-proof Properties of native and blended oil palm starch with nano-silicon dioxide as binder for particleboard Norani Abd Karim, Junidah Lamaming, Madihan Yusof, Rokiah Hashim, Othman Sulaiman, Salim Hiziroglu, Wan Noor Aidawati Wan Nadhari, Kushairi Mohd Salleh, Owolabi Folahan Taiwo PII:
S2352-7102(19)30058-0
DOI:
https://doi.org/10.1016/j.jobe.2019.101151
Reference:
JOBE 101151
To appear in:
Journal of Building Engineering
Received Date: 22 January 2019 Revised Date:
21 November 2019
Accepted Date: 23 December 2019
Please cite this article as: N.A. Karim, J. Lamaming, M. Yusof, R. Hashim, O. Sulaiman, S. Hiziroglu, W.N. Aidawati Wan Nadhari, K.M. Salleh, O.F. Taiwo, Properties of native and blended oil palm starch with nano-silicon dioxide as binder for particleboard, Journal of Building Engineering (2020), doi: https:// doi.org/10.1016/j.jobe.2019.101151. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Ltd.
Authors Contributions: Norani Abd Karim: Conceptualization, Methodology, Formal analysis, Writing- Original draft preparation. Junidah Lamaming: Visualization, Writing—Review & editing. Madihan Yusof: Investigation,Methodology. Rokiah Hashim: Conceptualization, Supervision, Funding acquisition, Writing—Review & editing. Othman Sulaiman: Funding acquisition. Salim Hiziroglu: Writing—Review & editing. Wan Noor Aidawati Wan Nadhari: Formal analysis. Kushairi Mohd Salleh: Formal analysis. Owolabi Folahan Taiwo: Writing— Review & editing.
1 2
Properties of native and blended oil palm starch with nano-silicon dioxide as binder for particleboard
3
Norani Abd Karima,b, Junidah Lamaminga, Madihan Yusofa, Rokiah Hashima*, Othman
4
Sulaimana, Salim Hizirogluc, Wan Noor Aidawati Wan Nadharid, Kushairi Mohd Salleha,
5
Owolabi Folahan Taiwoa,e
6
Contact information: aDivision of Bioresource, Paper and Coatings Technology, School of
7
Industrial Technology, Universiti Sains Malaysia, 11800 Penang, Malaysia; bPolytechnic
8
Kota Kinabalu, No 4,Jalan Politeknik, KKIP Barat, Kota Kinabalu Industrial Park, 88460,
9
Kota Kinabalu, Sabah, Malaysia; cDepartment of Natural Resource Ecology and
10
Management, Oklahoma State University, Stillwater, OK 74078-6013, USA; dDepartment of
11
Technical Foundation, Universiti Kuala Lumpur, Malaysian Institute of Chemical &
12
Bioengineering Technology, Lot 1988, Kawasan Perindustrian Bandar Vendor, Taboh
13
Naning, 78000 Alor Gajah, Melaka, Malaysia; e Federal Institute of Industrial Research
14
Oshodi Lagos, Nigeria.
15
*Corresponding author. Tel.: +60 4 653 5217; fax: +60 4 653 6375.
16 17 18 19 20
E-mail addresses: [email protected], [email protected] (R. Hashim*); [email protected] (N. Abd. Karim); [email protected] (J. Lamaming; [email protected] (M. Yusof); [email protected] (O. Sulaiman); [email protected] (S.Hiziroglu); [email protected] (W.N.A.Wan Nadhari); [email protected] (K.M.Salleh); [email protected] (O.F. Taiwo)
21
ABSTRACT
22
The replacement of the synthetic binder like urea formaldehyde and other suitable binder
23
with natural adhesive like starch is very challenging to meet acceptable properties. This study
24
evaluates the physicochemical and properties of both native starch and blended oil palm
25
starch from the mixture of polyvinyl alcohol, boric acid and nano silicon dioxide. The result
26
shows higher crystalline index and enthalpy peak of differentiate scanning calorimetry from
27
blended oil palm starch bonded particleboard in comparison with those bonded with native
28
starch. Morphological changes of native starch after blending process were observed from the
29
scanning electron micrograph. Improvement were seen in both the dimensional stability and 1
30
internal bond strength. The study shows that blended oil palm starch would be a potential
31
candidate as a green binder in particleboard production.
32
Keywords: starch; blended oil palm starch; bio-adhesive; polyvinyl alcohol; silicon dioxide
33
1.
34
Introduction The growth of oil palm plantations as an industrial crop in Malaysia has increased
35
exponentially [1] generating 13.97 million metric tons of oil palm trunk (OPT) every year [2-
36
3]. The oil palm trees of the age of 25 years or above are no longer considered as economical
37
and less suitable for cultivation [4]. Therefore, the uneconomical oil palm trees are cut down
38
and being replaced by the new trees plantation. The felled oil palm trees normally left on
39
harvesting site and not being utilized for any valuable products [1,5]. Several researches have
40
been reported on the proposed utilization of abandoned OPT by converting it into other
41
valuable products [6-7].
42
The oil palm biomass contains a substantial amount of starch in the whole plant but
43
more specifically in the trunk part [8-9]. Native starch is the mixture of glucose units of
44
amylose and amylopectin. Amylose is a small polymer and is an α-1,4-linked glucose units
45
with sometimes the long chains attached with α-1,6 branches (<1 % branching) whilst the
46
amylopectin is composed of an α-1,4-linked, α-1,6-branched (4-6 % branching) polymer [10].
47
According to Jarowenko (1977) [11], it is being used in various products including binders,
48
sizing materials, and pastes [12].
49
The oil palm starch (OPS) as a binder has a promising future to be seeen as a green
50
binder for particleboard manufacturing. The use of oil palm starch (OPS) as a binder for
51
wood composite is still new and has been explored by various researchers [1,13,14]. It has
52
been reported that the use of native OPS and modified OPS [1,12] in particleboard
53
manufacturing as binder exhibited a good mechanical property and met the requirement of
54
selected standard. In other work [13], the use of OPS as binder was compared with wheat 2
55
starch and the findings showed that particleboard with OPS have better properties than those
56
with wheat starch. However, it seems that starch based adhesives have some disadvantages
57
such as poor water resistant, mobility and bonding strength [15]. Characterization and
58
analysis of physicochemical properties of starch are important parameters to be studied so
59
that it could be used for various applications [16]. Previous research showed that modified
60
corn starch with polyvinyl alcohol (PVOH) and nano silicon dioxide (SiO2) improved
61
properties of packaging material [17]. However, there is very limited information on
62
physicochemical properties of OPS crosslinked with polyvinyl alcohol (PVA) and nano
63
silicon dioxide (SiO2) as a binder for particleboard manufacturing.
64
Particleboard is usually manufactured from wood particles or biomass materials such
65
as sawdust, wood shavings by bonding with synthetic adhesive under heat and pressure [18].
66
The commercial synthetic adhesive such as melamine formaldehyde, phenol formaldehyde,
67
and urea formaldehyde are commonly used adhesives that having excellent properties
68
including providing strong bonding, cost-effectiveness and fast curing time. It has been
69
reported [19] that such adhesives have one major disadvantage namely formaldehyde
70
emission causing environmental pollution and health hazard [20]. Natural adhesive such as
71
starch from different plants as a binder could provide alternative to commercial synthetic
72
adhesive to produce particleboard [13, 19, 21].
73
Several studies in modification of native starch for the particleboard production with
74
enhanced properties had been carried out [1,19,22]. The combination of starch and polyvinyl
75
alcohol (PVA) showed the best compatibility material [19,23]. The PVA enhance
76
particleboard properties such as excellent chemical resistant and good biocompatibility [23].
77
It also shows a biodegradable behavior when it is mixed with starch [24]. However, starch
78
and PVA have hydrophilic characteristics that can absorb moisture from the environment. A
79
water repellent additive probably is needed to overcome this problem [21]. The nano silicon
3
80
dioxide having a high value of hardness is widely used for many applications [25] and could
81
be suggested as a water repellent in natural adhesive such as starch [17]. Addition of this
82
water repellent to oil palm starch is expected to improve water resistant and mechanical
83
properties of particleboard. The blended oil palm starch can affect the physicochemical
84
properties and properties of starch based adhesives. Therefore, the objectives of this study are
85
to evaluate the performance of oil palm starch mixture based adhesive with the addition of
86
nano silicon dioxide (SiO2) and to evaluate their performance as a binder for particleboard.
87
The starch based adhesive properties, physicochemical and mechanical properties of
88
particleboard samples were evaluated according to Japanese Industrial standard (JIS) [26]
89
with acceptable properties.
90
2.
Materials and methods
91
2.1
Raw materials
92
Oil palm trunks (OPT) samples were obtained from local plantations in Kuala
93
Selangor, Malaysia, and cut into 5 cm discs. The oil palm discs were then cut to a smaller
94
size of approximately 0.5 cm for thickness and 6 cm width to facilitate the extraction process.
95
Raw material of 70 % Acacia mangium and 30 % mixed hardwoods (rubberwood and a few
96
types of tropical wood) was supplied by a local particleboard company in Negeri Sembilan,
97
Malaysia.
98
2.2
99
Oil palm starch extraction process The extraction process of the oil palm starch was conducted according to the previous
100
studies [1,8] with a slight modification in steeping time and mesh type used during the
101
extracting process. The samples were soaked in sodium metabisulphite with 1L of 0.005 g
102
(w/v) in aqueous solution. For each batch, approximately 6 discs were used and a total of 30
103
discs were used for this extraction process. Steeping was carried out for 48 h based on the
104
yield obtained from previous work [27]. After steeping, the starch was then extracted and
4
105
filtered through a mesh of sieve size 200 µm to avoid oil palm fibers being mixed with the
106
original starch. After the screening process, the samples were filtered and then centrifuged for
107
10 min at 3000 rpm using a centrifuge model Beckman Coulter Allegra X-15R. The sediment
108
starch at the bottom of the centrifuged bottle was removed and oven-dried at 60 °C ± 2 °C for
109
3 – 5 days. Then, the dried starch was grounded and stored in a sealed jar prior for further
110
use.
111
2.3
112
Starch blending and adhesive preparation process The PVA/starch blending was carried out based on process described in two previous
113
reports [17,28]. The extracted oil palm starch was placed in an oven at a temperature of 50 °C
114
to dry overnight before the blending process. The PVA with molar mass = 99.00 g/mol
115
(Sigma-Aldrich), boric acid (2 %), glycerol (20 %) and tween 80 (1 %) were used in this
116
study. All the materials were weighed based on adhesive modification formulation and
117
parameters set up for particleboard manufacturing as displayed in Table 1. Then 70 % of
118
starch with 30 % ratio of PVOH was prepared in this study and compared to 100 % native
119
starch and commercially produced UF. Distilled water solution of PVA was heated at a
120
temperature of 90 °C until it was completely dissolved. Then, the oil palm starch, glycerol,
121
boric acid, Tween 80 and 3 % of SiO2 were added to the mixture. All the solutions were
122
poured into a container and oven-dried at 60 °C before being used as a binder for
123
particleboard manufacturing.
124 125 126
Table 1. Starch blending ratio for particleboard manufacturing.
Sample type
Ratio Starch: Polyvinyl alcohol: Nano silicon dioxide (%)
Native starch
100: 0: 0
Blended starch (starch/PVA/SiO2)
70: 30: 3
Urea formaldehyde, UF (Control)
100: 0: 0 5
127 128
2.4
Evaluation of physicochemical properties of oil palm starch
129
Approximately 1 to 2 g of oil palm starch samples were placed in an oven at a
130
temperature of 105 °C for 24 h to determine their moisture content in duplicate. The samples
131
were then cooled down in a desiccator for about 10 min before determining their weight loss.
132
The pH measurement of the samples were done based on the procedure described by previous
133
researcher [16]. About 1.5 g of the starch was weighed in duplicate and placed in a 50 mL
134
extraction bottle before adding 25 mL of distilled water. Then, all the samples were mixed
135
with a portable shaker for 2 min and left for 10 min before measuring the pH value.
136
Particle size analysis was carried out by using the Mastersizer 2000 equipped with a
137
Scirocco dry powder feeder. In the next step, the particles size was measured and expressed
138
in micrometer (µm) units.
139
2.4.1 Determination of oil palm starch content
140
Determination of oil palm starch content was carried out by using method stated in
141
previous work by other researcher [29]. Approximately 0.4 g of the oil palm starch powder
142
was weighed and transferred to 50 mL centrifuge test tube. Then, 4 .7 mL of 7.2 M perchloric
143
acid was added, and the solution was allowed to react for 10 min with occasional stirring in
144
the water bath at 30 °C. After 10 min, the content was transferred to another 50 mL
145
centrifuge test tube and brought to volume. The sample was then centrifuged at 3000 rpm for
146
5 min. Then, 10 mL of solution was transferred into another 50 mL centrifuge test tube
147
together with phenolphthalein and turn to alkaline with 2 N sodium hydroxide. About 2 N
148
acetic acid was added to the solution until the color changed and then a further 2.5 mL was
149
added followed by 0.5 mL 10 % w/v potassium iodide and 5 mL 0.01 N potassium iodate.
150
The color was allowed to develop for 15 min before evaluation process. A UV-VIS
6
151
spectrophotometer was set at a wavelength of 650 nm used as the indicator in this
152
experiment. Three readings were collected for each type of sample.
153
2.4.2 Determination of protein content
154
Protein determination was adopted from previous method [30]. The process was
155
running by fully equipped automatic machine which consists of 3 steps. Firstly, digestion
156
with 2 mL sulfuric acid (98 % v/v) and 5 mg of Kjeldahl digestion tablet (catalyst) was used
157
in this process until transparent or nearly colorless solution was obtained in the flasks test
158
sample. Next, the distillation process used a 50 %, (w/v) of sodium hydroxide (NaOH) to
159
neutralize the sulfuric acid. Finally, titration process using 2 % of boric acid (H3BO3) reacted
160
with ammonia solution was conducted. About 1 - 2 g of duplicates of starch samples were
161
employed in this protein test. Lipid content was evaluated by using Soxtec TM 2050 (Auto Fat
162
Extraction System) equipment. About 90 mL of petroleum ether of 40 % – 60 % (v/v) was
163
used to extract the samples. About 1 – 2 g of samples were extracted within 2 h, oven dried at
164
100 °C for half an hour, placed in a desiccator to cool for 1 h until no further change in
165
weight, before the final weight of the sample was taken.
166
2.4.3 Determination of amylose content
167
Determination of amylose content followed a method by other study [31] using an
168
ethanol with 96 % (v/v) within 20 h for starch defatted by soxhlet extraction. A blank sample
169
was prepared at a concentration of 0 % to 40 % for control specimens. The test was
170
conducted in triplicate for each type of sample. Total amylose of starch sample was
171
calculated based on calibration graph from the blank samples by using a UV-VIS
172
spectrophotometer was set at a wavelength of 600 nm. Amylopectin value of the sample was
173
calculated based on equation stated in previous work [32].
174
Ash content method was adopted from previous work [16]. The duplicate sets of a
175
ceramic container containing a starch approximately 1 - 2 g were prepared and placed in a
7
176
muffle furnace at 550 °C for 3 h, then cooled in a desiccator for 1 h before weighing. The
177
percentage ash quantity of the oil palm starch sample was determined by weight differential
178
bases.
179
2.5
Determination of adhesive properties
180
The solid content of oil palm starch was measured by using a powder form sample in
181
a duplicate set [1]. Approximately 1 - 2 g of starch was weighed to obtain the initial weight,
182
before it was oven dried at 105 °C ± 2 °C temperature for 3 h. After 3 h, the samples were
183
placed in desiccators for approximately 10 min to reach a constant weight.
184
With the aid of viscometer model Brookfield DV-II + Pro, equipped with a spindle
185
size No. 0.7 the viscosity of adhesive of the extracted oil palm starch was measured at 100
186
rpm. Approximately 10 % (w/v) of the starch sample dissolved in 25 mL of distilled water
187
was placed in a 50 mL test tube. The sample was then heated in a water bath at a temperature
188
of 90 °C ± 2 °C for 10 min to allow each sample to dissolve completely. Later, the samples
189
were allowed to cool at ambient temperature for 10 min. Rheological properties of the
190
samples were analyzed with a three readings for each type of sample [27].
191
Evaluation of the Pot life of the prepared adhesive was embarked by preparing starch
192
water slurry at 80 °C temperature until it changed into a paste and left inside the container
193
until it became too thick to be spread. The time was monitored and recorded until the
194
adhesive become stable [33].
195
2.5.1 Swelling power and solubility determination
196
The swelling power and the solubility of the samples were carried out according to the
197
previous researcher [34]. Approximately 1 g of starch were weighed and poured into 50 mL
198
centrifuge tube with coated screw cap. About 10 mL of distilled water was added to the
199
sample dissolved. Each type of samples was prepared in triplicate for the experiment. Then,
200
all the tubes were shaken for 2 min with portable shaker before being heated at 50 °C, 60 °C,
8
201
70 °C, 80 °C and 90 °C for 40 min in a water bath for each different temperature respectively.
202
After heating, each sample was cooled to room temperature for 30 min and centrifuged at
203
3000 rpm for 20 min.
204
2.6
205
X-ray diffractometer (XRD) The percentage of a crystalline structure of the native starch and OPS was measured
206
using a Kristal- loflexD-5000 X-ray diffraction system (Siemens, Germany). This method
207
was adopted from the previous study [14]. The starch samples were placed in the sample
208
holder and packed before eliminating possible dust or any contamination by air blown. The
209
X-rays diffraction pattern were recorded using Cu Kα radiation for the scan measurement
210
were generated with an opening voltage of 40 kV and a current of 30 mA. The scanning
211
process was carried out at a 2θ diffraction angle ranging from 10–40º with 0.02 º and 2 º/min
212
scanning speed. The crystallinity index was calculated using Eq. (1) from the previous
213
method [35] (Segal et al., 1959):
214
C
215
where I200 is the peak intensity of the crystalline fraction and Iam is the peak intensity of the
216
amorphous fraction.
217
2.7 Thermal analysis of the sample
218
%
Eq. (1)
%
The thermal stability of both the blended and native sample were determined using
219
differential scanning calorimetry to compare the thermal stability of the blended starch
220
compared to that of the native starch. The melting temperature (Tm) of each type of starch
221
samples was determined using a Perkin Elmer Thermal analysis (Model DSC 8000). For this
222
study, about 5 mg each of the starch powder was weighed and put into an aluminum pan
223
which was subsequently placed in the instrument furnace along with an empty pan used as a
224
reference. At the preset temperature range between -15 °C and 280 °C under the nitrogen
225
atmosphere the samples were heated at the rate of 10 °C/min. 9
226
2.8
227
Morphological analysis The changes in the morphological structures of the native oil palm starch, and blended
228
starch samples were monitored using scanning electron microscopy (SEM). In this analysis,
229
the starch powder was dispersed and placed on a stub. The thin layer of gold was then coated
230
on the sample using a Polaron SC515 SEM coating system (Fisons Instrument).
231
Microstructure of the samples was evaluated by using a scanning electron microscope (Model
232
Supra 50 VP) with an accelerating voltage of 15 kV.
233
2.9
234
Manufacture of particleboard and evaluation of their properties Particleboard samples were produced based on a target density of 0.80 g/cm3 with the
235
dimensions of 20.1 cm x 20.1 cm x 0.5 cm. The particles used in this work recorded an 8 %
236
of moisture content (MC). Approximately 15 % of starch adhesive as prepared in the earlier
237
formulation was weighed based on dry weight (w/w). The starch adhesive was firstly mixed
238
with 150 mL of hot distilled water having temperature of 80 °C until it dissolved completely.
239
Then, it was poured into particles and mixed carefully until it covered all the particles
240
uniformly for about 5 to 7 min. The mixture was then placed into the mold to form a mat with
241
specified dimensional size, followed by cold pressing for about 2 min. A pressure of 5 MPa
242
was then applied on the mat, pressed with hot pressing at a temperature of 165 °C for 15 min.
243
The panels were cooled and placed in an air conditioning room at a temperature of 25 °C ± 2
244
°C with a relative humidity of 65 °C ± 2 °C for a week before further tests.
245
The physico-mechanical properties of the panel samples were evaluated in accordance
246
to JIS Standard A 5908 [26]. Moisture content (MC) value from an average of 5 samples was
247
taken based on oven dry weight. Density of the samples was calculated based on the product
248
of the dimensional measurement of the mass of the samples, the length, width, and the
249
thickness of the sample. The changes in value of the samples after the samples were soaked
250
for 2 h and 24 h in distilled water were noted. The differences in the thickness before and
10
251
after the immersion were used to determine the thickness swelling (TS) and water absorption
252
(WA) of the samples. Mechanical properties including the modulus of elasticity (MOE),
253
modulus of rupture (MOR) and internal bond (IB) strength were carried out by using an
254
Instron Tensile Machine Model 5582 with crosshead speed 10 mm/min and 2 mm/min.
255
2.10
Statistical analysis
256
All the test results were performed in five replicates and analyzed using SPSS
257
statistical software version 20.0 for Windows package for the analysis of variance (ANOVA)
258
while the post hoc test was conducted with Duncan`s multiple range test DMRT (p < 0.05) to
259
compare mean values at 5 % significance level. However, the physicochemical and adhesive
260
properties were expressed in standard deviation (SD).
261
3.0
262
3.1 Analysis of native starch and blended starch (starch/PVA/SiO2)
263
3.1.1
264
Results and Discussion
Physical and chemical properties of the starch The physicochemical properties of both native starch and blended oil palm starch
265
(starch/PVA/SiO2) are displayed in Table 2. The moisture content values of both native and
266
blended starch were 10.36 % and 23.98 %, respectively. Blended oil palm starch OPS showed
267
higher value as compared to that of native starch. The high MC of blended starch might be
268
attributed to the hydrophilic characteristics of oil palm starch and PVA which made it is easy
269
to absorb moisture from the environment during the blending process and the method storage
270
used for the starch might also contributed to the high MC [36].
271
Table 2.
272
Physical and chemical analysis for both native and blended oil palm starch. Properties
Native starch
Blended starch (starch/PVA/SiO2)
MC (%)
10.36 (0.76)
23.98 (1.83)
pH
4.66 (0.02)
5.63 (0.08) 11
273 274
Particle size (µm)
21.99 (0.71)
17.15 (0.1)
Starch content (%)
6.00 (0.05)
19.75 (6.79)
Amylose (%)
10.87 (0.01)
9.26 (0.01)
Amylopectin (%)
89.13 (0.01)
90.74 (0.01)
Protein (%)
2.17 (0.01)
0.90 (0.08)
Lipid (%)
1.00 (0.01)
0.00 (0.00)
Ash (%)
3.37 (0.05)
2.93 (0.1)
Note: Data is expressed as means; values in parentheses show standard deviations. The pH values for both starches were acidic, with the pH value of the native starch
275
and blended starch measured at 4.66 and 5.63, respectively. From the result, the blended
276
starch is more favored since acidic property enhances better bonding process between binders
277
and wood fibers [13].
278
The granules sizes for both native and blended oil palm starch were 21.99 µm and
279
17.15 µm, respectively. This was the highest value as compared to that of previous work
280
obtained which are in average between 11.00 µm to 13.00 µm [1,13]. A different source of
281
botanical, sampling used, mesh wire size of 200 µm and combination with other additives
282
such as PVA and SiO2 in blended starch may have influenced the results.
283
Starch content obtained in this study was 6.0 % for native starch and 19.75 % for
284
blended starch. The blending process had increased the starch content in the blended oil palm
285
starch which could be attributed to the possibility of cross-linking that might happened
286
between starch and other compounds in the starch-based adhesive. However, further work is
287
required to confirm on this issue. Lower starch content reflected the amylose and amylopectin
288
ratio and purity of the starch that could affect the particleboard properties.
289
Amylose and amylopectin of both starches were also measured. Amylose content of
290
the sample was 10.87 % for native starch and 9.26 % for blended starch/PVA/SiO2.
291
Amylopectin value of 89.13 % and 90.74 % were found for native and blended starch,
292
respectively. Since amylose is insoluble and amylopectin is soluble in water, adhesive 12
293
produced from the blended starch are more soluble and the capability to absorb water was
294
higher [13] as compared to native starch. Water repellent of the sample was lower when
295
amylopectin value is greater. The amylose content of starch affects starch solution properties
296
such as starch solubility and swelling power, which depend on the leaching of amylose out of
297
the crystalline network of amylopectin into solution [36]. In the starch-based application, the
298
amylose content is one of the crucial factors that need to be take account of since the ratio of
299
amylose to amylopectin elucidates the starch applicability [37].
300
Protein content value of both starches was measured and it shows that native starch is
301
having a higher percentage of 2.17 % compared to blended starch, which has 0.90 % of
302
protein. It is known that higher protein content could affect the starch swelling properties due
303
to the proteinaceous materials surrounded the starch granules that can swell rapidly upon
304
hydration [13]. The protein can also affect the starch gelatinization and pasting properties
305
[36]. Higher protein value found in the native starch is an agreement with those of previous
306
work that explain the inefficient removal of protein from the starch sample could contribute
307
to the high value of protein [8].
308
Highest lipid content was found in native oil palm starch (1.00 %) compared to
309
blended oil palm starch that having a value of 0 %. High amylose content in the starch
310
indicates higher lipid content and vice versa. From the findings, the lipid content of both
311
starches were in agreement with the amylose content aforementioned. The native starch is
312
having higher lipid content in accordance to the higher amylose content as compared to
313
blended starch.
314
The higher value 3.37 % of ash content was found in the native oil palm starch, and
315
blended starch/PVA/SiO2 having a value of 2.93 %. The ash content will reflect the purity of
316
starch. The native oil palm starch has higher ash content due to higher silica content in oil
317
palm trunk [8].
13
318
3.1.2
Adhesive analysis
319
Adhesive properties of oil palm trunk starch such as solid content, viscosity and pot
320
life are displayed in Table 3. Percentage of solid content for both native and blended starch
321
was 31.82 % and 24.42 % respectively. The solid content of native starch recorded slightly
322
higher compared to blended starch. The solid content of native starch in this study was found
323
higher while blended starch was lower as compared to previous studies that used native starch
324
and modified starch from oil palm trunk and [1,37]. Different treatments during extraction
325
process and blending/modification process possibly contribute to the difference in the solid
326
content value. However, a value of 24.42 % from blended starch in this study is an agreement
327
with an earlier study [19], suggesting that the solid content should have 27 % or less for
328
better bonding properties.
329
Table 3.
330
Adhesive properties of native and blended oil palm starch. Adhesive properties Type of samples Native starch Blended starch (starch/PVA/SiO2)
331 332 333
Solid content at 105° ± 2°C (%) 31.82 (2.52)
Viscosity at 80 °C (Centipoises, cP) 105.67 (3.06)
Pot life (days) 2.00 (1.41)
24.42 (4.02)
187.67 (12.90)
2.50 (0.71)
Note: Data is expressed as means; values in parentheses show standard deviations.
Native oil palm starch sample obtained a low viscosity value (105.67 cP) compared to
334
blended starch sample having a value of 187.67 cP. This finding was similar to the previous
335
study reported by other researcher [1]. Higher viscosity value of adhesive is required when it
336
acts as an adhesive. It is worth noting that starch originated from different sources and parts
337
of plant also has an influence on the viscosity value [38].
338 339
The pot life of native and blended starch was slightly different from each other. Blended starch had longer pot life of 2.5 days compared to 2 days of native starch. The pot 14
340
life depends on the viscosity of the starch. The higher the viscosity, the less time it will
341
needed for the adhesive to be spread. However, this finding was contradicted with the
342
previous study where native starch has longer pot life compared to blended starch [1]. Natural
343
adhesive commonly was unstable in the room temperature, thus it will shorten the shelf life of
344
this adhesive [39] compared to blended starch based adhesive. This finding could be due to
345
nano silicon dioxide (SiO2) in the samples protecting starch based from absorbing moisture in
346
the environment. Thus, it enhanced the blended adhesive’s shelf life in contrast to the native
347
starch.
348
Table 4 depicted the swelling power and solubility of both native and blended starch
349
at five different temperature. The blended starch/PVA/SiO2 showed higher swelling power
350
values compared to the native starch. The result showed that gradual increment in swelling
351
was shown in both starch before decreasing at temperature of 80 °C for native starch and 90
352
°C for blended starch. The native oil palm starch had the higher swelling power at a
353
temperature of 70 ºC and 80 ºC for blended oil palm starch. Higher solubility values were
354
ranged from 5.23 to 19.05 % to % of native starch as compared to blended starch ranged from
355
0.50 % to 3.38 %. Higher swelling power and lower solubility found in the starch/PVA/SiO2
356
at a temperature of 80 ºC was enhanced the adhesion properties thus improved the internal
357
bonding and dimensional stability.
358
Table 4.
359
Swelling and solubility for native and blended oil palm starch. Temperature (°C)
50
60
Type of sample
SP (g)
Native starch
2.52 17.17 (1.93) (13.24)
SOL (%)
70
80
90
SP (g)
SOL (%)
SP (g)
SOL (%)
SP (g)
SOL (%)
SP (g)
SOL (%)
2.78 (0.35)
19.05 (6.25)
6.90 (5.05)
7.46 (0.88)
6.53 (6.57)
5.23 (2.10)
5.19 (3.90)
2.89 (0.76)
15
360 361 362 363
2.59 24.01 8.64 0.50 10.49 2.80 19.10 0.88 14.17 3.38 Blended (1.95) (0.58) (1.14) (0.12) (1.44) (2.72) (1.64) (0.53) (1.20) (3.30) starch (starch/PVA/ SiO2) Note: Data is expressed as means: values in parentheses show standard deviations; SPswelling power, SOL- solubility.
3.1.3
XRD analysis Native oil palm starch had the lowest crystalline index value recorded at 14.03°
364
compared to blended starch/PVA/SiO2 which had a value at 23 º as illustrated in Fig. 1. The
366
crystalline index value for native starch and starch/PVA/SiO2 calculated were 20.24 % and
367
29.52 %, respectively. Lowest crystalline index in native starch was similar to previous
368
research [1]. This result might be due to the highest amylose content in native oil palm starch
369
that tends to give a lower crystalline index [13]. The results indicated that the crystallinity of
370
the blended starch tends to increase after blending process. Higher crystallinity of oil palm
371
starch can affects the percentage of swelling and solubility, gelatinization temperature and
372
also the reaction enthalpy of the samples [8]. All the results of this study were considered as
373
Type A pattern as agreement with the previous study where the peaks are between 14 °C to
374
24 °C [8].
Intensity counts
365
10000 9000 8000 7000 6000 5000 4000 3000 2000 1000 0
Blended starch
Native starch
4
6
8
10
12
14
16
18
2 Theta 375 16
20
22
24
26
29
376
Fig. 1. XRD patterns for native oil palm starch and blended starch (starch/PVA/SiO2).
377
3.1.4
DSC thermal analysis
378
The result in Fig. 2 shows the DSC thermograms of native oil palm starch and
379
blended starch/PVOH/SiO2. The DSC thermograms showed that the native starch has a peak
380
melting temperature (Tm) of 78.30 °C and the blended starch showing a higher value of Tm at
381
124.36 °C. The glass transition temperature (Tg) of native starch is 11.98 °C, which is lower
382
compared to blended starch which is 70.81 °C. The total enthalpy of gelanization of native
383
starch recorded at 210.28 J/g, higher than that of blended starch (172.01 J/g). Increased in
384
melting temperature for blended starch occurred in this work ascribed to the cross linking
385
reaction between oil palm starch, PVA and nano silicon dioxide (SiO2). The higher enthalpy
386
value will contribute to higher temperature that needed to break up the linkages when OPS
387
adhesive is used as a particleboard binder. Previous study also confirmed that oil palm trunk
388
has a higher molecular organization, structural conformation, and crystallinity compared to
389
another type of starch such as sago, sweet potato, cassava, and water chestnut [8]. Previous
390
work done by Sulaiman et al. (2013) also reported that thermal properties of blended starch
391
improved in contrast to native starch, due to changes in the chemical structure during the
392
modification process [13].
17
393 394 395
Fig. 2. DSC thermogram of native oil palm starch and blended oil palm starch (starch/PVA/SiO2).
396
3.1.5
397
SEM analysis The micrograph images of both the native and blended oil palm starch are shown in
398
Figs. 3 (a) and (b). The SEM images were taken at 2000X magnification and the shape for all
399
the samples is round to oval shape. This finding has similar trend as found by a previous
400
researcher [8] which reported the ovoid and elliptical shape and some bell shaped granules.
401
The SEM analysis revealed that blended oil palm starch granules changed to agglomerate
402
form and covered by PVA and nano silica dioxide (SiO2) on the surface of starch granules
403
after the blending process. The granules size for native oil palm sample was bigger than
404
blended samples so that they tend to enhance overall strength of the panels.
18
a
b
405
Fig. 3. Scanning electron micrograph morphology of (a) native oil palm starch and (b)
406
blended oil palm starch (starch /PVA/SiO2).
407
3.2
408
Properties of particleboard samples Table 5 displays the results of physical and mechanical properties of particleboard
409
panels made using the native starch, blended starch (starch starch/PVA/SiO2) and UF
410
(control) as a binder. The density of particleboard bonded with native oil palm starch had a
411
value of 0.81 g/cm3. Samples having blended oil palm starch/PVA/SiO2 and control samples
412
made with UF had density values of 0.78 g/cm3 and 0.70 g/cm3, respectively. The uneven
413
distribution of particles and binders in the furnish influenced the results. Duncan`s groupings
414
also supported this finding, where control board (UF) was significantly different at p < 0.05.
415
Board achieved the target density which indicated that good bonding has occurred between
416
starch based adhesive and particles. Other study was reported that board with high density
417
will perform excellent particleboard properties [40].
418
Moisture content (MC) of board bonded with native oil palm starch was obtained 6.80
419
% and board bonded with blended starch/PVA/SiO2 and UF obtained the values of 6.87 %
420
and 7.31 %, respectively. The highest MC value of 7.31 % was found in the control board
421
(UF). Duncan`s groupings also revealed that control sample (UF) showed a significant
422
different at p < 0.05.
19
423
Table 5.
424
Physical and mechanical properties of native and blended oil palm starch. Sample type
Physical properties Measured Density (g/cm3)
425 426
Moisture content MC (%)
Mechanical properties Thickness swelling (%)
Water absorption (%)
2h
24 h
2h
24 h
MOR N/ mm2
MOE N/ mm2
IB N/ mm2
Native starch
0.81 (0.03)b
6.80 (0.17)a
34.67 (4.87)a
45.44 (2.27)b
49.89 (9.15)a
108.64 (10.48)b
16.19 (1.87)b
2702.02 (248.90)b
1.38 (0.96)a
Blended starch (starch/PVA/SiO2)
0.78 (0.03)b
6.87 (0.23)a
34.00 (4.55)a
34.63 (7.78)a
84.47 (8.57)b
88.82 (10.15)a
12.39 (2.89)a
2150.55 (347.89)a
2.16 (1.03)b
Urea formaldehyde (UF)
0.70 (0.03)a
7.31 (0.15)b
33.39 (3.07)a
36.01 (1.89)a
93.75 (13.63)b
91.37 (9.31)a
12.24 (2.87)a
2039.10 (468.77)a
5.20 (0.84)c
Note: Data is expressed as means; values in parentheses show standard deviations. Values with the same letter are not significantly different (p< 0.05).
20
427
The native oil palm starch achieved a higher value of thickness swelling (TS) at 2 h
428
(34.67 %) and 24 h (45.44%). Board bonded with blended starch/PVA/SiO2 with TS value of
429
34.63 % recorded a lower value when immersed in water for 24 h as compared to board
430
bonded with native starch and urea formaldehyde (UF). The addition of nano silicon dioxide
431
(SiO2) with starch in blended oil palm starch improved TS value of the samples. Excellent
432
bonding properties between particles and interaction of nano SiO2 with other compounds in
433
the starch-based adhesive are evidence for improving thickness swelling value of the samples
434
[41].
435
The WA value of 88.82 % and 108.64 % corresponding to lowest and highest values
436
were found for board bonded with blended oil palm starch/PVOH/SiO2 and native oil palm
437
starch, respectively for 24 h soaking time. Based on Duncan`s grouping analysis, only board
438
with native starch was significantly different at p< 0.05. However, both TS and WA in this
439
study did not satisfy the minimum requirement (12 %) for Type 8 in JIS standard A 5908.
440
The highest value of modulus of elasticity (MOE) was found for board bonded with
441
native oil palm starch (2702.02 N/mm2). The higher amount of starch typically reflects the
442
higher ratio of amylose to amylopectin [1]. Board bonded with blended starch/PVA/SiO2,
443
showed higher value (2150.55 N/mm2) as compared to the control board (UF) obtained a
444
value of 2039.10 N/mm2. All the boards fulfilled the minimum standard for Type 8 in JIS
445
standard A 5908 for MOE results (2000 N/mm2).
446
Modulus of rupture (MOR) in this study also had showed the similar trend as MOE
447
values where both particleboards with native oil palm starch showed the highest value that is
448
16.19 N/mm2. A similar trend as MOE performance was also shown in board bonded with
449
blended oil palm starch/PVA/SiO2 achieved 12.39 N/mm2 slightly higher than control board
450
(UF) has a value 12.24 N/mm2. All the boards also fulfilled the minimum standard for Type 8
451
in JIS standard A 5908 for MOR results (8 N/mm2). For internal bond (IB) strength test, as 21
452
expected boards bonded with UF showed the higher value 5.20 N/mm2 as compared to
453
blended oil palm starch/PVA/SiO2 and native starch has a value of 2.16 N/mm2 and 1.38
454
N/mm2, respectively. All the boards had passed the minimum requirement of JIS Standard
455
for type 8 (0.15 N/mm2). The addition of SiO2 in the samples resulted in significant effect in
456
enhancing the internal bond strength of particleboard specimens bonded with blended oil
457
palm starch. Other factors such as particle size, chemical composition in starch granules [13],
458
and purity of starch [1] also influenced overall properties of the samples.
459
4.
460
Conclusions Based on the findings in this study, blended oil palm starch with polyvinyl alcohol
461
and nano silicon dioxide (SiO2), had a significant effect on physicochemical properties. Both
462
native starch and blended oil palm starch properties positively influenced the final
463
performance of the particleboard as a binder. The starch content ratio also affected the
464
mechanical properties of the particleboard. All the panels of the particleboard bonded using
465
native and blended oil palm starch in this study satisfied the Japanese Industrial Standards
466
(JIS) Type 8 for mechanical properties including MOE, MOR, and IB. However
467
improvement in dimensional stability of the samples is necessary. The study further revealed
468
that incorporation of additives such as SiO2 is capable of enhancing the TS and the WA
469
characteristics of the samples. This study indicated that blended oil palm starch with
470
polyvinyl alcohol and nano silicon dioxide (SiO2) would have the potential candidate as a
471
binder for particleboard production in the future.
472
Acknowledgements
473
We would like to acknowledge Universiti Sains Malaysia for the research grant (100/
474
PTEKIND/815066 and 1001/PTEKIND/ 8014083) to carry out this research project and
475
postdoctoral fellowship awarded to Dr. Junidah Lamaming Dr. Owolabi Folahan Taiwo and
22
476
graduate assistant to Madihan Yusof. Graduate study scholarship awarded to Norani Abd
477
Karim by Ministry Of Higher Education, Malaysia is also acknowledged.
478
Conflict of Interest
479
We declare there is no conflict of interest.
480
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27
Highlights •
New source of starch extracted from oil palm trunk.
•
Modification with PVOH and addition of nano silicon dioxide (SiO2).
•
Physicochemical properties altered the properties of starch based adhesives.
•
Starch ratios influenced the board panel’s properties.
•
SiO2 had significant influenced the dimensional stability.
S2352-7102(19)30058-0
DOI:
https://doi.org/10.1016/j.jobe.2019.101151
Reference:
JOBE 101151
To appear in:
Journal of Building Engineering
Received Date: 22 January 2019 Revised Date:
21 November 2019
Accepted Date: 23 December 2019
Please cite this article as: N.A. Karim, J. Lamaming, M. Yusof, R. Hashim, O. Sulaiman, S. Hiziroglu, W.N. Aidawati Wan Nadhari, K.M. Salleh, O.F. Taiwo, Properties of native and blended oil palm starch with nano-silicon dioxide as binder for particleboard, Journal of Building Engineering (2020), doi: https:// doi.org/10.1016/j.jobe.2019.101151. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Ltd.
Authors Contributions: Norani Abd Karim: Conceptualization, Methodology, Formal analysis, Writing- Original draft preparation. Junidah Lamaming: Visualization, Writing—Review & editing. Madihan Yusof: Investigation,Methodology. Rokiah Hashim: Conceptualization, Supervision, Funding acquisition, Writing—Review & editing. Othman Sulaiman: Funding acquisition. Salim Hiziroglu: Writing—Review & editing. Wan Noor Aidawati Wan Nadhari: Formal analysis. Kushairi Mohd Salleh: Formal analysis. Owolabi Folahan Taiwo: Writing— Review & editing.
1 2
Properties of native and blended oil palm starch with nano-silicon dioxide as binder for particleboard
3
Norani Abd Karima,b, Junidah Lamaminga, Madihan Yusofa, Rokiah Hashima*, Othman
4
Sulaimana, Salim Hizirogluc, Wan Noor Aidawati Wan Nadharid, Kushairi Mohd Salleha,
5
Owolabi Folahan Taiwoa,e
6
Contact information: aDivision of Bioresource, Paper and Coatings Technology, School of
7
Industrial Technology, Universiti Sains Malaysia, 11800 Penang, Malaysia; bPolytechnic
8
Kota Kinabalu, No 4,Jalan Politeknik, KKIP Barat, Kota Kinabalu Industrial Park, 88460,
9
Kota Kinabalu, Sabah, Malaysia; cDepartment of Natural Resource Ecology and
10
Management, Oklahoma State University, Stillwater, OK 74078-6013, USA; dDepartment of
11
Technical Foundation, Universiti Kuala Lumpur, Malaysian Institute of Chemical &
12
Bioengineering Technology, Lot 1988, Kawasan Perindustrian Bandar Vendor, Taboh
13
Naning, 78000 Alor Gajah, Melaka, Malaysia; e Federal Institute of Industrial Research
14
Oshodi Lagos, Nigeria.
15
*Corresponding author. Tel.: +60 4 653 5217; fax: +60 4 653 6375.
16 17 18 19 20
E-mail addresses: [email protected], [email protected] (R. Hashim*); [email protected] (N. Abd. Karim); [email protected] (J. Lamaming; [email protected] (M. Yusof); [email protected] (O. Sulaiman); [email protected] (S.Hiziroglu); [email protected] (W.N.A.Wan Nadhari); [email protected] (K.M.Salleh); [email protected] (O.F. Taiwo)
21
ABSTRACT
22
The replacement of the synthetic binder like urea formaldehyde and other suitable binder
23
with natural adhesive like starch is very challenging to meet acceptable properties. This study
24
evaluates the physicochemical and properties of both native starch and blended oil palm
25
starch from the mixture of polyvinyl alcohol, boric acid and nano silicon dioxide. The result
26
shows higher crystalline index and enthalpy peak of differentiate scanning calorimetry from
27
blended oil palm starch bonded particleboard in comparison with those bonded with native
28
starch. Morphological changes of native starch after blending process were observed from the
29
scanning electron micrograph. Improvement were seen in both the dimensional stability and 1
30
internal bond strength. The study shows that blended oil palm starch would be a potential
31
candidate as a green binder in particleboard production.
32
Keywords: starch; blended oil palm starch; bio-adhesive; polyvinyl alcohol; silicon dioxide
33
1.
34
Introduction The growth of oil palm plantations as an industrial crop in Malaysia has increased
35
exponentially [1] generating 13.97 million metric tons of oil palm trunk (OPT) every year [2-
36
3]. The oil palm trees of the age of 25 years or above are no longer considered as economical
37
and less suitable for cultivation [4]. Therefore, the uneconomical oil palm trees are cut down
38
and being replaced by the new trees plantation. The felled oil palm trees normally left on
39
harvesting site and not being utilized for any valuable products [1,5]. Several researches have
40
been reported on the proposed utilization of abandoned OPT by converting it into other
41
valuable products [6-7].
42
The oil palm biomass contains a substantial amount of starch in the whole plant but
43
more specifically in the trunk part [8-9]. Native starch is the mixture of glucose units of
44
amylose and amylopectin. Amylose is a small polymer and is an α-1,4-linked glucose units
45
with sometimes the long chains attached with α-1,6 branches (<1 % branching) whilst the
46
amylopectin is composed of an α-1,4-linked, α-1,6-branched (4-6 % branching) polymer [10].
47
According to Jarowenko (1977) [11], it is being used in various products including binders,
48
sizing materials, and pastes [12].
49
The oil palm starch (OPS) as a binder has a promising future to be seeen as a green
50
binder for particleboard manufacturing. The use of oil palm starch (OPS) as a binder for
51
wood composite is still new and has been explored by various researchers [1,13,14]. It has
52
been reported that the use of native OPS and modified OPS [1,12] in particleboard
53
manufacturing as binder exhibited a good mechanical property and met the requirement of
54
selected standard. In other work [13], the use of OPS as binder was compared with wheat 2
55
starch and the findings showed that particleboard with OPS have better properties than those
56
with wheat starch. However, it seems that starch based adhesives have some disadvantages
57
such as poor water resistant, mobility and bonding strength [15]. Characterization and
58
analysis of physicochemical properties of starch are important parameters to be studied so
59
that it could be used for various applications [16]. Previous research showed that modified
60
corn starch with polyvinyl alcohol (PVOH) and nano silicon dioxide (SiO2) improved
61
properties of packaging material [17]. However, there is very limited information on
62
physicochemical properties of OPS crosslinked with polyvinyl alcohol (PVA) and nano
63
silicon dioxide (SiO2) as a binder for particleboard manufacturing.
64
Particleboard is usually manufactured from wood particles or biomass materials such
65
as sawdust, wood shavings by bonding with synthetic adhesive under heat and pressure [18].
66
The commercial synthetic adhesive such as melamine formaldehyde, phenol formaldehyde,
67
and urea formaldehyde are commonly used adhesives that having excellent properties
68
including providing strong bonding, cost-effectiveness and fast curing time. It has been
69
reported [19] that such adhesives have one major disadvantage namely formaldehyde
70
emission causing environmental pollution and health hazard [20]. Natural adhesive such as
71
starch from different plants as a binder could provide alternative to commercial synthetic
72
adhesive to produce particleboard [13, 19, 21].
73
Several studies in modification of native starch for the particleboard production with
74
enhanced properties had been carried out [1,19,22]. The combination of starch and polyvinyl
75
alcohol (PVA) showed the best compatibility material [19,23]. The PVA enhance
76
particleboard properties such as excellent chemical resistant and good biocompatibility [23].
77
It also shows a biodegradable behavior when it is mixed with starch [24]. However, starch
78
and PVA have hydrophilic characteristics that can absorb moisture from the environment. A
79
water repellent additive probably is needed to overcome this problem [21]. The nano silicon
3
80
dioxide having a high value of hardness is widely used for many applications [25] and could
81
be suggested as a water repellent in natural adhesive such as starch [17]. Addition of this
82
water repellent to oil palm starch is expected to improve water resistant and mechanical
83
properties of particleboard. The blended oil palm starch can affect the physicochemical
84
properties and properties of starch based adhesives. Therefore, the objectives of this study are
85
to evaluate the performance of oil palm starch mixture based adhesive with the addition of
86
nano silicon dioxide (SiO2) and to evaluate their performance as a binder for particleboard.
87
The starch based adhesive properties, physicochemical and mechanical properties of
88
particleboard samples were evaluated according to Japanese Industrial standard (JIS) [26]
89
with acceptable properties.
90
2.
Materials and methods
91
2.1
Raw materials
92
Oil palm trunks (OPT) samples were obtained from local plantations in Kuala
93
Selangor, Malaysia, and cut into 5 cm discs. The oil palm discs were then cut to a smaller
94
size of approximately 0.5 cm for thickness and 6 cm width to facilitate the extraction process.
95
Raw material of 70 % Acacia mangium and 30 % mixed hardwoods (rubberwood and a few
96
types of tropical wood) was supplied by a local particleboard company in Negeri Sembilan,
97
Malaysia.
98
2.2
99
Oil palm starch extraction process The extraction process of the oil palm starch was conducted according to the previous
100
studies [1,8] with a slight modification in steeping time and mesh type used during the
101
extracting process. The samples were soaked in sodium metabisulphite with 1L of 0.005 g
102
(w/v) in aqueous solution. For each batch, approximately 6 discs were used and a total of 30
103
discs were used for this extraction process. Steeping was carried out for 48 h based on the
104
yield obtained from previous work [27]. After steeping, the starch was then extracted and
4
105
filtered through a mesh of sieve size 200 µm to avoid oil palm fibers being mixed with the
106
original starch. After the screening process, the samples were filtered and then centrifuged for
107
10 min at 3000 rpm using a centrifuge model Beckman Coulter Allegra X-15R. The sediment
108
starch at the bottom of the centrifuged bottle was removed and oven-dried at 60 °C ± 2 °C for
109
3 – 5 days. Then, the dried starch was grounded and stored in a sealed jar prior for further
110
use.
111
2.3
112
Starch blending and adhesive preparation process The PVA/starch blending was carried out based on process described in two previous
113
reports [17,28]. The extracted oil palm starch was placed in an oven at a temperature of 50 °C
114
to dry overnight before the blending process. The PVA with molar mass = 99.00 g/mol
115
(Sigma-Aldrich), boric acid (2 %), glycerol (20 %) and tween 80 (1 %) were used in this
116
study. All the materials were weighed based on adhesive modification formulation and
117
parameters set up for particleboard manufacturing as displayed in Table 1. Then 70 % of
118
starch with 30 % ratio of PVOH was prepared in this study and compared to 100 % native
119
starch and commercially produced UF. Distilled water solution of PVA was heated at a
120
temperature of 90 °C until it was completely dissolved. Then, the oil palm starch, glycerol,
121
boric acid, Tween 80 and 3 % of SiO2 were added to the mixture. All the solutions were
122
poured into a container and oven-dried at 60 °C before being used as a binder for
123
particleboard manufacturing.
124 125 126
Table 1. Starch blending ratio for particleboard manufacturing.
Sample type
Ratio Starch: Polyvinyl alcohol: Nano silicon dioxide (%)
Native starch
100: 0: 0
Blended starch (starch/PVA/SiO2)
70: 30: 3
Urea formaldehyde, UF (Control)
100: 0: 0 5
127 128
2.4
Evaluation of physicochemical properties of oil palm starch
129
Approximately 1 to 2 g of oil palm starch samples were placed in an oven at a
130
temperature of 105 °C for 24 h to determine their moisture content in duplicate. The samples
131
were then cooled down in a desiccator for about 10 min before determining their weight loss.
132
The pH measurement of the samples were done based on the procedure described by previous
133
researcher [16]. About 1.5 g of the starch was weighed in duplicate and placed in a 50 mL
134
extraction bottle before adding 25 mL of distilled water. Then, all the samples were mixed
135
with a portable shaker for 2 min and left for 10 min before measuring the pH value.
136
Particle size analysis was carried out by using the Mastersizer 2000 equipped with a
137
Scirocco dry powder feeder. In the next step, the particles size was measured and expressed
138
in micrometer (µm) units.
139
2.4.1 Determination of oil palm starch content
140
Determination of oil palm starch content was carried out by using method stated in
141
previous work by other researcher [29]. Approximately 0.4 g of the oil palm starch powder
142
was weighed and transferred to 50 mL centrifuge test tube. Then, 4 .7 mL of 7.2 M perchloric
143
acid was added, and the solution was allowed to react for 10 min with occasional stirring in
144
the water bath at 30 °C. After 10 min, the content was transferred to another 50 mL
145
centrifuge test tube and brought to volume. The sample was then centrifuged at 3000 rpm for
146
5 min. Then, 10 mL of solution was transferred into another 50 mL centrifuge test tube
147
together with phenolphthalein and turn to alkaline with 2 N sodium hydroxide. About 2 N
148
acetic acid was added to the solution until the color changed and then a further 2.5 mL was
149
added followed by 0.5 mL 10 % w/v potassium iodide and 5 mL 0.01 N potassium iodate.
150
The color was allowed to develop for 15 min before evaluation process. A UV-VIS
6
151
spectrophotometer was set at a wavelength of 650 nm used as the indicator in this
152
experiment. Three readings were collected for each type of sample.
153
2.4.2 Determination of protein content
154
Protein determination was adopted from previous method [30]. The process was
155
running by fully equipped automatic machine which consists of 3 steps. Firstly, digestion
156
with 2 mL sulfuric acid (98 % v/v) and 5 mg of Kjeldahl digestion tablet (catalyst) was used
157
in this process until transparent or nearly colorless solution was obtained in the flasks test
158
sample. Next, the distillation process used a 50 %, (w/v) of sodium hydroxide (NaOH) to
159
neutralize the sulfuric acid. Finally, titration process using 2 % of boric acid (H3BO3) reacted
160
with ammonia solution was conducted. About 1 - 2 g of duplicates of starch samples were
161
employed in this protein test. Lipid content was evaluated by using Soxtec TM 2050 (Auto Fat
162
Extraction System) equipment. About 90 mL of petroleum ether of 40 % – 60 % (v/v) was
163
used to extract the samples. About 1 – 2 g of samples were extracted within 2 h, oven dried at
164
100 °C for half an hour, placed in a desiccator to cool for 1 h until no further change in
165
weight, before the final weight of the sample was taken.
166
2.4.3 Determination of amylose content
167
Determination of amylose content followed a method by other study [31] using an
168
ethanol with 96 % (v/v) within 20 h for starch defatted by soxhlet extraction. A blank sample
169
was prepared at a concentration of 0 % to 40 % for control specimens. The test was
170
conducted in triplicate for each type of sample. Total amylose of starch sample was
171
calculated based on calibration graph from the blank samples by using a UV-VIS
172
spectrophotometer was set at a wavelength of 600 nm. Amylopectin value of the sample was
173
calculated based on equation stated in previous work [32].
174
Ash content method was adopted from previous work [16]. The duplicate sets of a
175
ceramic container containing a starch approximately 1 - 2 g were prepared and placed in a
7
176
muffle furnace at 550 °C for 3 h, then cooled in a desiccator for 1 h before weighing. The
177
percentage ash quantity of the oil palm starch sample was determined by weight differential
178
bases.
179
2.5
Determination of adhesive properties
180
The solid content of oil palm starch was measured by using a powder form sample in
181
a duplicate set [1]. Approximately 1 - 2 g of starch was weighed to obtain the initial weight,
182
before it was oven dried at 105 °C ± 2 °C temperature for 3 h. After 3 h, the samples were
183
placed in desiccators for approximately 10 min to reach a constant weight.
184
With the aid of viscometer model Brookfield DV-II + Pro, equipped with a spindle
185
size No. 0.7 the viscosity of adhesive of the extracted oil palm starch was measured at 100
186
rpm. Approximately 10 % (w/v) of the starch sample dissolved in 25 mL of distilled water
187
was placed in a 50 mL test tube. The sample was then heated in a water bath at a temperature
188
of 90 °C ± 2 °C for 10 min to allow each sample to dissolve completely. Later, the samples
189
were allowed to cool at ambient temperature for 10 min. Rheological properties of the
190
samples were analyzed with a three readings for each type of sample [27].
191
Evaluation of the Pot life of the prepared adhesive was embarked by preparing starch
192
water slurry at 80 °C temperature until it changed into a paste and left inside the container
193
until it became too thick to be spread. The time was monitored and recorded until the
194
adhesive become stable [33].
195
2.5.1 Swelling power and solubility determination
196
The swelling power and the solubility of the samples were carried out according to the
197
previous researcher [34]. Approximately 1 g of starch were weighed and poured into 50 mL
198
centrifuge tube with coated screw cap. About 10 mL of distilled water was added to the
199
sample dissolved. Each type of samples was prepared in triplicate for the experiment. Then,
200
all the tubes were shaken for 2 min with portable shaker before being heated at 50 °C, 60 °C,
8
201
70 °C, 80 °C and 90 °C for 40 min in a water bath for each different temperature respectively.
202
After heating, each sample was cooled to room temperature for 30 min and centrifuged at
203
3000 rpm for 20 min.
204
2.6
205
X-ray diffractometer (XRD) The percentage of a crystalline structure of the native starch and OPS was measured
206
using a Kristal- loflexD-5000 X-ray diffraction system (Siemens, Germany). This method
207
was adopted from the previous study [14]. The starch samples were placed in the sample
208
holder and packed before eliminating possible dust or any contamination by air blown. The
209
X-rays diffraction pattern were recorded using Cu Kα radiation for the scan measurement
210
were generated with an opening voltage of 40 kV and a current of 30 mA. The scanning
211
process was carried out at a 2θ diffraction angle ranging from 10–40º with 0.02 º and 2 º/min
212
scanning speed. The crystallinity index was calculated using Eq. (1) from the previous
213
method [35] (Segal et al., 1959):
214
C
215
where I200 is the peak intensity of the crystalline fraction and Iam is the peak intensity of the
216
amorphous fraction.
217
2.7 Thermal analysis of the sample
218
%
Eq. (1)
%
The thermal stability of both the blended and native sample were determined using
219
differential scanning calorimetry to compare the thermal stability of the blended starch
220
compared to that of the native starch. The melting temperature (Tm) of each type of starch
221
samples was determined using a Perkin Elmer Thermal analysis (Model DSC 8000). For this
222
study, about 5 mg each of the starch powder was weighed and put into an aluminum pan
223
which was subsequently placed in the instrument furnace along with an empty pan used as a
224
reference. At the preset temperature range between -15 °C and 280 °C under the nitrogen
225
atmosphere the samples were heated at the rate of 10 °C/min. 9
226
2.8
227
Morphological analysis The changes in the morphological structures of the native oil palm starch, and blended
228
starch samples were monitored using scanning electron microscopy (SEM). In this analysis,
229
the starch powder was dispersed and placed on a stub. The thin layer of gold was then coated
230
on the sample using a Polaron SC515 SEM coating system (Fisons Instrument).
231
Microstructure of the samples was evaluated by using a scanning electron microscope (Model
232
Supra 50 VP) with an accelerating voltage of 15 kV.
233
2.9
234
Manufacture of particleboard and evaluation of their properties Particleboard samples were produced based on a target density of 0.80 g/cm3 with the
235
dimensions of 20.1 cm x 20.1 cm x 0.5 cm. The particles used in this work recorded an 8 %
236
of moisture content (MC). Approximately 15 % of starch adhesive as prepared in the earlier
237
formulation was weighed based on dry weight (w/w). The starch adhesive was firstly mixed
238
with 150 mL of hot distilled water having temperature of 80 °C until it dissolved completely.
239
Then, it was poured into particles and mixed carefully until it covered all the particles
240
uniformly for about 5 to 7 min. The mixture was then placed into the mold to form a mat with
241
specified dimensional size, followed by cold pressing for about 2 min. A pressure of 5 MPa
242
was then applied on the mat, pressed with hot pressing at a temperature of 165 °C for 15 min.
243
The panels were cooled and placed in an air conditioning room at a temperature of 25 °C ± 2
244
°C with a relative humidity of 65 °C ± 2 °C for a week before further tests.
245
The physico-mechanical properties of the panel samples were evaluated in accordance
246
to JIS Standard A 5908 [26]. Moisture content (MC) value from an average of 5 samples was
247
taken based on oven dry weight. Density of the samples was calculated based on the product
248
of the dimensional measurement of the mass of the samples, the length, width, and the
249
thickness of the sample. The changes in value of the samples after the samples were soaked
250
for 2 h and 24 h in distilled water were noted. The differences in the thickness before and
10
251
after the immersion were used to determine the thickness swelling (TS) and water absorption
252
(WA) of the samples. Mechanical properties including the modulus of elasticity (MOE),
253
modulus of rupture (MOR) and internal bond (IB) strength were carried out by using an
254
Instron Tensile Machine Model 5582 with crosshead speed 10 mm/min and 2 mm/min.
255
2.10
Statistical analysis
256
All the test results were performed in five replicates and analyzed using SPSS
257
statistical software version 20.0 for Windows package for the analysis of variance (ANOVA)
258
while the post hoc test was conducted with Duncan`s multiple range test DMRT (p < 0.05) to
259
compare mean values at 5 % significance level. However, the physicochemical and adhesive
260
properties were expressed in standard deviation (SD).
261
3.0
262
3.1 Analysis of native starch and blended starch (starch/PVA/SiO2)
263
3.1.1
264
Results and Discussion
Physical and chemical properties of the starch The physicochemical properties of both native starch and blended oil palm starch
265
(starch/PVA/SiO2) are displayed in Table 2. The moisture content values of both native and
266
blended starch were 10.36 % and 23.98 %, respectively. Blended oil palm starch OPS showed
267
higher value as compared to that of native starch. The high MC of blended starch might be
268
attributed to the hydrophilic characteristics of oil palm starch and PVA which made it is easy
269
to absorb moisture from the environment during the blending process and the method storage
270
used for the starch might also contributed to the high MC [36].
271
Table 2.
272
Physical and chemical analysis for both native and blended oil palm starch. Properties
Native starch
Blended starch (starch/PVA/SiO2)
MC (%)
10.36 (0.76)
23.98 (1.83)
pH
4.66 (0.02)
5.63 (0.08) 11
273 274
Particle size (µm)
21.99 (0.71)
17.15 (0.1)
Starch content (%)
6.00 (0.05)
19.75 (6.79)
Amylose (%)
10.87 (0.01)
9.26 (0.01)
Amylopectin (%)
89.13 (0.01)
90.74 (0.01)
Protein (%)
2.17 (0.01)
0.90 (0.08)
Lipid (%)
1.00 (0.01)
0.00 (0.00)
Ash (%)
3.37 (0.05)
2.93 (0.1)
Note: Data is expressed as means; values in parentheses show standard deviations. The pH values for both starches were acidic, with the pH value of the native starch
275
and blended starch measured at 4.66 and 5.63, respectively. From the result, the blended
276
starch is more favored since acidic property enhances better bonding process between binders
277
and wood fibers [13].
278
The granules sizes for both native and blended oil palm starch were 21.99 µm and
279
17.15 µm, respectively. This was the highest value as compared to that of previous work
280
obtained which are in average between 11.00 µm to 13.00 µm [1,13]. A different source of
281
botanical, sampling used, mesh wire size of 200 µm and combination with other additives
282
such as PVA and SiO2 in blended starch may have influenced the results.
283
Starch content obtained in this study was 6.0 % for native starch and 19.75 % for
284
blended starch. The blending process had increased the starch content in the blended oil palm
285
starch which could be attributed to the possibility of cross-linking that might happened
286
between starch and other compounds in the starch-based adhesive. However, further work is
287
required to confirm on this issue. Lower starch content reflected the amylose and amylopectin
288
ratio and purity of the starch that could affect the particleboard properties.
289
Amylose and amylopectin of both starches were also measured. Amylose content of
290
the sample was 10.87 % for native starch and 9.26 % for blended starch/PVA/SiO2.
291
Amylopectin value of 89.13 % and 90.74 % were found for native and blended starch,
292
respectively. Since amylose is insoluble and amylopectin is soluble in water, adhesive 12
293
produced from the blended starch are more soluble and the capability to absorb water was
294
higher [13] as compared to native starch. Water repellent of the sample was lower when
295
amylopectin value is greater. The amylose content of starch affects starch solution properties
296
such as starch solubility and swelling power, which depend on the leaching of amylose out of
297
the crystalline network of amylopectin into solution [36]. In the starch-based application, the
298
amylose content is one of the crucial factors that need to be take account of since the ratio of
299
amylose to amylopectin elucidates the starch applicability [37].
300
Protein content value of both starches was measured and it shows that native starch is
301
having a higher percentage of 2.17 % compared to blended starch, which has 0.90 % of
302
protein. It is known that higher protein content could affect the starch swelling properties due
303
to the proteinaceous materials surrounded the starch granules that can swell rapidly upon
304
hydration [13]. The protein can also affect the starch gelatinization and pasting properties
305
[36]. Higher protein value found in the native starch is an agreement with those of previous
306
work that explain the inefficient removal of protein from the starch sample could contribute
307
to the high value of protein [8].
308
Highest lipid content was found in native oil palm starch (1.00 %) compared to
309
blended oil palm starch that having a value of 0 %. High amylose content in the starch
310
indicates higher lipid content and vice versa. From the findings, the lipid content of both
311
starches were in agreement with the amylose content aforementioned. The native starch is
312
having higher lipid content in accordance to the higher amylose content as compared to
313
blended starch.
314
The higher value 3.37 % of ash content was found in the native oil palm starch, and
315
blended starch/PVA/SiO2 having a value of 2.93 %. The ash content will reflect the purity of
316
starch. The native oil palm starch has higher ash content due to higher silica content in oil
317
palm trunk [8].
13
318
3.1.2
Adhesive analysis
319
Adhesive properties of oil palm trunk starch such as solid content, viscosity and pot
320
life are displayed in Table 3. Percentage of solid content for both native and blended starch
321
was 31.82 % and 24.42 % respectively. The solid content of native starch recorded slightly
322
higher compared to blended starch. The solid content of native starch in this study was found
323
higher while blended starch was lower as compared to previous studies that used native starch
324
and modified starch from oil palm trunk and [1,37]. Different treatments during extraction
325
process and blending/modification process possibly contribute to the difference in the solid
326
content value. However, a value of 24.42 % from blended starch in this study is an agreement
327
with an earlier study [19], suggesting that the solid content should have 27 % or less for
328
better bonding properties.
329
Table 3.
330
Adhesive properties of native and blended oil palm starch. Adhesive properties Type of samples Native starch Blended starch (starch/PVA/SiO2)
331 332 333
Solid content at 105° ± 2°C (%) 31.82 (2.52)
Viscosity at 80 °C (Centipoises, cP) 105.67 (3.06)
Pot life (days) 2.00 (1.41)
24.42 (4.02)
187.67 (12.90)
2.50 (0.71)
Note: Data is expressed as means; values in parentheses show standard deviations.
Native oil palm starch sample obtained a low viscosity value (105.67 cP) compared to
334
blended starch sample having a value of 187.67 cP. This finding was similar to the previous
335
study reported by other researcher [1]. Higher viscosity value of adhesive is required when it
336
acts as an adhesive. It is worth noting that starch originated from different sources and parts
337
of plant also has an influence on the viscosity value [38].
338 339
The pot life of native and blended starch was slightly different from each other. Blended starch had longer pot life of 2.5 days compared to 2 days of native starch. The pot 14
340
life depends on the viscosity of the starch. The higher the viscosity, the less time it will
341
needed for the adhesive to be spread. However, this finding was contradicted with the
342
previous study where native starch has longer pot life compared to blended starch [1]. Natural
343
adhesive commonly was unstable in the room temperature, thus it will shorten the shelf life of
344
this adhesive [39] compared to blended starch based adhesive. This finding could be due to
345
nano silicon dioxide (SiO2) in the samples protecting starch based from absorbing moisture in
346
the environment. Thus, it enhanced the blended adhesive’s shelf life in contrast to the native
347
starch.
348
Table 4 depicted the swelling power and solubility of both native and blended starch
349
at five different temperature. The blended starch/PVA/SiO2 showed higher swelling power
350
values compared to the native starch. The result showed that gradual increment in swelling
351
was shown in both starch before decreasing at temperature of 80 °C for native starch and 90
352
°C for blended starch. The native oil palm starch had the higher swelling power at a
353
temperature of 70 ºC and 80 ºC for blended oil palm starch. Higher solubility values were
354
ranged from 5.23 to 19.05 % to % of native starch as compared to blended starch ranged from
355
0.50 % to 3.38 %. Higher swelling power and lower solubility found in the starch/PVA/SiO2
356
at a temperature of 80 ºC was enhanced the adhesion properties thus improved the internal
357
bonding and dimensional stability.
358
Table 4.
359
Swelling and solubility for native and blended oil palm starch. Temperature (°C)
50
60
Type of sample
SP (g)
Native starch
2.52 17.17 (1.93) (13.24)
SOL (%)
70
80
90
SP (g)
SOL (%)
SP (g)
SOL (%)
SP (g)
SOL (%)
SP (g)
SOL (%)
2.78 (0.35)
19.05 (6.25)
6.90 (5.05)
7.46 (0.88)
6.53 (6.57)
5.23 (2.10)
5.19 (3.90)
2.89 (0.76)
15
360 361 362 363
2.59 24.01 8.64 0.50 10.49 2.80 19.10 0.88 14.17 3.38 Blended (1.95) (0.58) (1.14) (0.12) (1.44) (2.72) (1.64) (0.53) (1.20) (3.30) starch (starch/PVA/ SiO2) Note: Data is expressed as means: values in parentheses show standard deviations; SPswelling power, SOL- solubility.
3.1.3
XRD analysis Native oil palm starch had the lowest crystalline index value recorded at 14.03°
364
compared to blended starch/PVA/SiO2 which had a value at 23 º as illustrated in Fig. 1. The
366
crystalline index value for native starch and starch/PVA/SiO2 calculated were 20.24 % and
367
29.52 %, respectively. Lowest crystalline index in native starch was similar to previous
368
research [1]. This result might be due to the highest amylose content in native oil palm starch
369
that tends to give a lower crystalline index [13]. The results indicated that the crystallinity of
370
the blended starch tends to increase after blending process. Higher crystallinity of oil palm
371
starch can affects the percentage of swelling and solubility, gelatinization temperature and
372
also the reaction enthalpy of the samples [8]. All the results of this study were considered as
373
Type A pattern as agreement with the previous study where the peaks are between 14 °C to
374
24 °C [8].
Intensity counts
365
10000 9000 8000 7000 6000 5000 4000 3000 2000 1000 0
Blended starch
Native starch
4
6
8
10
12
14
16
18
2 Theta 375 16
20
22
24
26
29
376
Fig. 1. XRD patterns for native oil palm starch and blended starch (starch/PVA/SiO2).
377
3.1.4
DSC thermal analysis
378
The result in Fig. 2 shows the DSC thermograms of native oil palm starch and
379
blended starch/PVOH/SiO2. The DSC thermograms showed that the native starch has a peak
380
melting temperature (Tm) of 78.30 °C and the blended starch showing a higher value of Tm at
381
124.36 °C. The glass transition temperature (Tg) of native starch is 11.98 °C, which is lower
382
compared to blended starch which is 70.81 °C. The total enthalpy of gelanization of native
383
starch recorded at 210.28 J/g, higher than that of blended starch (172.01 J/g). Increased in
384
melting temperature for blended starch occurred in this work ascribed to the cross linking
385
reaction between oil palm starch, PVA and nano silicon dioxide (SiO2). The higher enthalpy
386
value will contribute to higher temperature that needed to break up the linkages when OPS
387
adhesive is used as a particleboard binder. Previous study also confirmed that oil palm trunk
388
has a higher molecular organization, structural conformation, and crystallinity compared to
389
another type of starch such as sago, sweet potato, cassava, and water chestnut [8]. Previous
390
work done by Sulaiman et al. (2013) also reported that thermal properties of blended starch
391
improved in contrast to native starch, due to changes in the chemical structure during the
392
modification process [13].
17
393 394 395
Fig. 2. DSC thermogram of native oil palm starch and blended oil palm starch (starch/PVA/SiO2).
396
3.1.5
397
SEM analysis The micrograph images of both the native and blended oil palm starch are shown in
398
Figs. 3 (a) and (b). The SEM images were taken at 2000X magnification and the shape for all
399
the samples is round to oval shape. This finding has similar trend as found by a previous
400
researcher [8] which reported the ovoid and elliptical shape and some bell shaped granules.
401
The SEM analysis revealed that blended oil palm starch granules changed to agglomerate
402
form and covered by PVA and nano silica dioxide (SiO2) on the surface of starch granules
403
after the blending process. The granules size for native oil palm sample was bigger than
404
blended samples so that they tend to enhance overall strength of the panels.
18
a
b
405
Fig. 3. Scanning electron micrograph morphology of (a) native oil palm starch and (b)
406
blended oil palm starch (starch /PVA/SiO2).
407
3.2
408
Properties of particleboard samples Table 5 displays the results of physical and mechanical properties of particleboard
409
panels made using the native starch, blended starch (starch starch/PVA/SiO2) and UF
410
(control) as a binder. The density of particleboard bonded with native oil palm starch had a
411
value of 0.81 g/cm3. Samples having blended oil palm starch/PVA/SiO2 and control samples
412
made with UF had density values of 0.78 g/cm3 and 0.70 g/cm3, respectively. The uneven
413
distribution of particles and binders in the furnish influenced the results. Duncan`s groupings
414
also supported this finding, where control board (UF) was significantly different at p < 0.05.
415
Board achieved the target density which indicated that good bonding has occurred between
416
starch based adhesive and particles. Other study was reported that board with high density
417
will perform excellent particleboard properties [40].
418
Moisture content (MC) of board bonded with native oil palm starch was obtained 6.80
419
% and board bonded with blended starch/PVA/SiO2 and UF obtained the values of 6.87 %
420
and 7.31 %, respectively. The highest MC value of 7.31 % was found in the control board
421
(UF). Duncan`s groupings also revealed that control sample (UF) showed a significant
422
different at p < 0.05.
19
423
Table 5.
424
Physical and mechanical properties of native and blended oil palm starch. Sample type
Physical properties Measured Density (g/cm3)
425 426
Moisture content MC (%)
Mechanical properties Thickness swelling (%)
Water absorption (%)
2h
24 h
2h
24 h
MOR N/ mm2
MOE N/ mm2
IB N/ mm2
Native starch
0.81 (0.03)b
6.80 (0.17)a
34.67 (4.87)a
45.44 (2.27)b
49.89 (9.15)a
108.64 (10.48)b
16.19 (1.87)b
2702.02 (248.90)b
1.38 (0.96)a
Blended starch (starch/PVA/SiO2)
0.78 (0.03)b
6.87 (0.23)a
34.00 (4.55)a
34.63 (7.78)a
84.47 (8.57)b
88.82 (10.15)a
12.39 (2.89)a
2150.55 (347.89)a
2.16 (1.03)b
Urea formaldehyde (UF)
0.70 (0.03)a
7.31 (0.15)b
33.39 (3.07)a
36.01 (1.89)a
93.75 (13.63)b
91.37 (9.31)a
12.24 (2.87)a
2039.10 (468.77)a
5.20 (0.84)c
Note: Data is expressed as means; values in parentheses show standard deviations. Values with the same letter are not significantly different (p< 0.05).
20
427
The native oil palm starch achieved a higher value of thickness swelling (TS) at 2 h
428
(34.67 %) and 24 h (45.44%). Board bonded with blended starch/PVA/SiO2 with TS value of
429
34.63 % recorded a lower value when immersed in water for 24 h as compared to board
430
bonded with native starch and urea formaldehyde (UF). The addition of nano silicon dioxide
431
(SiO2) with starch in blended oil palm starch improved TS value of the samples. Excellent
432
bonding properties between particles and interaction of nano SiO2 with other compounds in
433
the starch-based adhesive are evidence for improving thickness swelling value of the samples
434
[41].
435
The WA value of 88.82 % and 108.64 % corresponding to lowest and highest values
436
were found for board bonded with blended oil palm starch/PVOH/SiO2 and native oil palm
437
starch, respectively for 24 h soaking time. Based on Duncan`s grouping analysis, only board
438
with native starch was significantly different at p< 0.05. However, both TS and WA in this
439
study did not satisfy the minimum requirement (12 %) for Type 8 in JIS standard A 5908.
440
The highest value of modulus of elasticity (MOE) was found for board bonded with
441
native oil palm starch (2702.02 N/mm2). The higher amount of starch typically reflects the
442
higher ratio of amylose to amylopectin [1]. Board bonded with blended starch/PVA/SiO2,
443
showed higher value (2150.55 N/mm2) as compared to the control board (UF) obtained a
444
value of 2039.10 N/mm2. All the boards fulfilled the minimum standard for Type 8 in JIS
445
standard A 5908 for MOE results (2000 N/mm2).
446
Modulus of rupture (MOR) in this study also had showed the similar trend as MOE
447
values where both particleboards with native oil palm starch showed the highest value that is
448
16.19 N/mm2. A similar trend as MOE performance was also shown in board bonded with
449
blended oil palm starch/PVA/SiO2 achieved 12.39 N/mm2 slightly higher than control board
450
(UF) has a value 12.24 N/mm2. All the boards also fulfilled the minimum standard for Type 8
451
in JIS standard A 5908 for MOR results (8 N/mm2). For internal bond (IB) strength test, as 21
452
expected boards bonded with UF showed the higher value 5.20 N/mm2 as compared to
453
blended oil palm starch/PVA/SiO2 and native starch has a value of 2.16 N/mm2 and 1.38
454
N/mm2, respectively. All the boards had passed the minimum requirement of JIS Standard
455
for type 8 (0.15 N/mm2). The addition of SiO2 in the samples resulted in significant effect in
456
enhancing the internal bond strength of particleboard specimens bonded with blended oil
457
palm starch. Other factors such as particle size, chemical composition in starch granules [13],
458
and purity of starch [1] also influenced overall properties of the samples.
459
4.
460
Conclusions Based on the findings in this study, blended oil palm starch with polyvinyl alcohol
461
and nano silicon dioxide (SiO2), had a significant effect on physicochemical properties. Both
462
native starch and blended oil palm starch properties positively influenced the final
463
performance of the particleboard as a binder. The starch content ratio also affected the
464
mechanical properties of the particleboard. All the panels of the particleboard bonded using
465
native and blended oil palm starch in this study satisfied the Japanese Industrial Standards
466
(JIS) Type 8 for mechanical properties including MOE, MOR, and IB. However
467
improvement in dimensional stability of the samples is necessary. The study further revealed
468
that incorporation of additives such as SiO2 is capable of enhancing the TS and the WA
469
characteristics of the samples. This study indicated that blended oil palm starch with
470
polyvinyl alcohol and nano silicon dioxide (SiO2) would have the potential candidate as a
471
binder for particleboard production in the future.
472
Acknowledgements
473
We would like to acknowledge Universiti Sains Malaysia for the research grant (100/
474
PTEKIND/815066 and 1001/PTEKIND/ 8014083) to carry out this research project and
475
postdoctoral fellowship awarded to Dr. Junidah Lamaming Dr. Owolabi Folahan Taiwo and
22
476
graduate assistant to Madihan Yusof. Graduate study scholarship awarded to Norani Abd
477
Karim by Ministry Of Higher Education, Malaysia is also acknowledged.
478
Conflict of Interest
479
We declare there is no conflict of interest.
480
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27
Highlights •
New source of starch extracted from oil palm trunk.
•
Modification with PVOH and addition of nano silicon dioxide (SiO2).
•
Physicochemical properties altered the properties of starch based adhesives.
•
Starch ratios influenced the board panel’s properties.
•
SiO2 had significant influenced the dimensional stability.