Effect of agro waste α-cellulosic micro filler on mechanical and thermal behavior of epoxy composites

Journal Pre-proof Effect of agro waste α-cellulosic micro filler on mechanical and thermal behavior of epoxy composites

K.J. Nagarajan, A.N. Balaji, K. Sathick Basha, N.R. Ramanujam, R. Ashok Kumar PII:

S0141-8130(20)30285-3

DOI:

https://doi.org/10.1016/j.ijbiomac.2020.02.255

Reference:

BIOMAC 14872

To appear in:

International Journal of Biological Macromolecules

Received date:

10 January 2020

Revised date:

19 February 2020

Accepted date:

22 February 2020

Please cite this article as: K.J. Nagarajan, A.N. Balaji, K.S. Basha, et al., Effect of agro waste α-cellulosic micro filler on mechanical and thermal behavior of epoxy composites, International Journal of Biological Macromolecules(2020), https://doi.org/10.1016/ j.ijbiomac.2020.02.255

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© 2020 Published by Elsevier.

Journal Pre-proof

Effect of agro waste α-cellulosic micro filler on mechanical and thermal behavior of epoxy composites K.J.Nagarajana*, A.N.Balajib , K. Sathick Bashac, N.R.Ramanujamd, R. Ashok kumare a, b,e

Department of Mechanical Engineering, K.L.N. College of Engineering, Pottapalayam, Tamil Nadu, India,

c

Department of Mechanical Engineering, B.S. Abdur Rahman Crescent Institute of Science and Technology, Chennai, Tamil Nadu, India, Department of Physics, K.L.N. College of Engineering, Pottapalayam, Tamil Nadu, India,

corresponding author email: [email protected];

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*

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Abstract

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Of late, measures are being undertaken to curtail deforestation thereby to save the environment. In this venture, agro waste products are utilized for structural

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applications instead of wood. By this way, the α-cellulosic micro filler, which are

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isolated from Cocos nucifera var Aurantiaca Peduncle (CAP) through chemical treatment process, are systematically utilized as a reinforcing material in thermo set

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epoxy polymers as a replacement by manmade carbon, ceramic fillers and wood derived products. The results on mechanical properties such as tensile, flexural, impact test revealed that these properties of the α-cellulosic micro filler reinforced epoxy composites increased in linear nature for 3 wt.% to 15 wt.% of filler loading and 15 wt % shows the superior behaviour in their mechanical properties. The internal structure of the fractured mechanical test specimens are investigated through Field Emission Scanning Electron Microscopy (FE-SEM). In addition to that, visco-elastic behaviour, thermal stability of the 15 wt.% of α-cellulosic micro filler reinforced epoxy composite were analyzed through dynamic mechanical and thermo gravimetric analysis and compare with pristine epoxy. 1

Journal Pre-proof Keywords:

α-cellulosic

micro

filler;

Epoxy

composite;

Mechanical

properties;

Morphological properties; Thermal stability.

1. INTRODUCTION In recent years, the demand for products is made from sustainable and renewable resources such as non-petroleum based, biodegradable, availability of carbon in nature [1, 2]. Concerning the above, the researchers all over the universe have been focused to

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incorporate the organic materials as a reinforcement material into the polymer matrix

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especially for engineering structural applications. Hence, the composite materials based on natural fiber as utilized by the engineering industry sectors for the past few years [3].

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The natural fiber-based composite materials are used in many static and dynamic

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applications like automobiles, sports equipment, constructions, electronic and food packing

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industries [4]. Specifically, in automobile sectors (Audi Group, BMW, Daimler Chrysler, Ford, Mercedes, and Volkswagen) utilized the natural fiber-based composite materials in

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various automobile parts such as coconut fibers rubber latex composites for the seats (Mercedes Benz A-class),fax-sisal fiber mat reinforced epoxy composite for car door panels

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(Mercedes Benz E-class model), sisal mat reinforced polyurethane composite for door trim panels (Audi), kenaf fibers reinforced composites for door panels (Ford Mondeo) and BMW Group has a lot of natural fiber-reinforced composites into its automobiles [3]. In the latest trends, the material researchers are focused in developing the organic micro fillers reinforced composites due to their attractive features such as good aspect ratio, stiffness, low density, eco-friendly, recyclable, and larger surface to volume ratio, which provides a better mechanical properties when compared to short or long fiber reinforced polymer composites [5]. The production cost of organic fillers is much lower than the cost of synthetic fillers [6, 7]. 2

Journal Pre-proof Enormous number of research works was carried out based on the plant fiber (short fiber/ woven mat) reinforced polymer composites. However, this is not the case with exploration on micro cellulosic filler reinforcement. Some of the cellulosic fillers derived from the plant fibers, which were used as reinforcement in the past, are biochar, Arundo donax, wood dust, sunflower stalks, pee nut, pine needles, and jatropha curcas L etc. [8-14]. Therefore, the utilization of micro-level fillers that are gained from natural fibers has a broader scope in the research field. Stalin et al. [15] developed a tamarind seed filler

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reinforced with vinyl ester composite, by using the compression mold method. They

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investigated the properties such as tensile, flexural and impact strength of tamarind seed filler

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composites. They concluded that the tensile, flexural and impact strengths are increased by

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39%, 55% and 21.5%, respectively with 15 wt.% filler reinforcement in matrix. Similarly, Naga Prasad et al. [16] prepared a powder form of date palm seed through the ball milling

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process, which was used as a reinforcement material in the vinyl ester polymer matrix by

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using the compression molding method. A 30 wt.% of date palm seed powder-filled composite indicates better results in thermal and mechanical properties.

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Further, Vignesh [17] et al studied the effect of mechanical properties on wood sawdust filler of Indian mallow fiber yarn mat reinforced with polyester composites. They concluded that the double-layered Indian mallow fiber on longitudinal direction of yarn mat with sawdust filler reinforced polyester composites has the optimum value of tensile strength of 65 MPa, flexural strength of 220 MPa, and impact strength of 295kJ/m2 due to better bonding between the reinforcement and the matrix material with uniform dispersion of particulate into the matrix. Vinod [18] et al. comparatively analyzed the jute fiber reinforced epoxy composite with different calotropis gigantea Stem particulate (5-10%wt.) loading and without the particulate content. Through their studies, they observed that the Calotropis gigantea Stem particulate (10wt.%) reinforced epoxy composite exhibits an optimum tensile 3

Journal Pre-proof strength of 48.73 MPa, and the flexural strength of 195.19 MPa. Santhosh et al. [19] also studied the effect of 5 wt.% rice husk particulate on alkali-treated prosopis juliflora reinforced epoxy composite which provides a better tensile and flexural strength than other composites equipped with different wt.% of particulate content. From the literature survey, it is evident that the mechanical and the thermal properties of the polymer composites improved due to the incorporation of cellulosic filler material. The literature discloses that there is still an opportunity to analyze the mechanical, thermal and morphological behaviour from the

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wasted cellulosic filler (from agricultural waste) reinforced polymer composite to meet the

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worldwide demand partially.

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In the latest trend, the research attitude of the researchers is towards developing the α-

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cellulosic micro fillers from the new biomass sources to be used for large scale of polymer composite applications. Cellulose, a biopolymer, is the main component of all plant fibers

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and is created by repeating the link of β–D–glucopyranose [20, 21]. This cellulose is derived

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from lingo-cellulosic fibers such as wood, natural plant fibers and agricultural residues etc., Besides the low production cost, biodegradability and renewability, the α-cellulosic micro

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fillers have drawn much attention among the researchers in the field of material science and it fulfils the industry requirements. Due to these features, the micro-fillers exhibit a unique capacity to improve the mechanical, surface morphology and thermal properties of the polymer composites [22,23]. Various methods such as the chemical, biological, mechanical and combined processes are utilized for the extraction of α-cellulosic fillers from the plant resources [24–26]. Among these, the chemical treatment is one of the low-cost methods that produces α-cellulosic micro fillers very effectively by removing the maximum amount of non-cellulosic from the natural fiber by increasing the moisture resistance property and crystalline size of the fibers as well [27]. One of the most commonly used chemical treatments to eliminate the non-cellulosic materials from the fibers is an integrated process 4

Journal Pre-proof consisting of acidified-chlorination, alkalization, and acid hydrolysis. Besides, this process breaks the polymerization of the cellulose chains and consequently the diameter of the fibers, which get reduced to a micron range. Moreover, it is a continuous process with the utilization of a limited amount of acids and it produces a particle in micron range with a low production cost [28]. A large amount of wasted cellulosic material in the Asian region necessitates the utilization of bio-waste as filler in polymer matrices, which has gained attention today.

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The Cocos nucifera var aurantiaca is one of the most renewable and sustainable

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resources of cellulose fibers plant, which belongs to the Arecaceae (palm family),

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abundantly available in worldwide humid tropical zones. On the global scale, coconut is

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grown in about 12.9 Million hectares (Mha) over 90 countries, with an annual production of about 61.2 billion nuts. Among the Asian countries, India is one of the

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leading coconut growing nations with a production of about 15.73 billion nuts in an area

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of 1.89 Mha at average productivity of 8300 fruits per ha [29]. Coir is one of the classical natural fiber which is extracted from the fruit husk and utilized for producing

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products such as floor mats, doormats, brushes, mattresses and reinforcing material in polymer materials [29]. However, the peduncles have been considered as a waste product by harvesters, are discarded in the earth, and are one of the major components in the agricultural solid waste management system. Open dumping causes problems related to land use and environment. Conversion of this cellulosic biomass into reinforcing material for polymer matrix and the pressure reduces handling of this waste to solid waste management community. The authors [30] evaluated the feasibility of using alkali treated Cocos nucifera var Aurantiaca Peduncle as a source for the reinforcement of thermo set composites. In particular, the fibers, which are extracted from the Peduncle and their chemical composition, microstructure, and mechanical 5

Journal Pre-proof properties, were investigated [30]. Yet, there has been no concrete approach to make use of α-cellulosic micro fillers from Cocos nucifera var Aurantiaca Peduncle as potential reinforcing filler. Hence, in the present work, chemical treatment (acidifiedchlorination, alkalization, and acid hydrolysis) is utilized for producing α-cellulosic micro fillers from Cocos nucifera var Aurantiaca Peduncle. Further, this study revolves around the reinforcing effect of α-cellulosic filler in epoxy composites is investigated through various techniques of tensile test, flexural test, impact test, Dynamic

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Mechanical Analysis (DMA), Fourier Transform Infrared spectroscopy (FT-IR) and

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Thermo Gravimetric Analysis (TGA). The microstructure of the fractured α-cellulosic

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filler reinforced epoxy composite specimens was analyzed through Field Emission-

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Scanning Electron Microscope (FE-SEM).

MATERIALS AND METHODS

2.1

Materials

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2.

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The Cocos nucifera var Aurantiaca Peduncles (CAPs) were collected from Pollachi, Coimbatore district, Tamil Nadu, India. Acetic acid, sodium chlorite, sodium hydroxide

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pellets, sodium bisulfite, nitric acid, toluene and ethanol (Sd-Fine Chemicals) chemicals were purchased from Sigma–Aldrich, Bangaluru, Karnataka, India. Diglycidyl ether of bisphenol A (DGEBA) epoxy LY556 with density 1.15-1.2g/cm3, Aliphatic Primary Amine hardener (HY951) with density 0.97 g/cm3 and Afra silicone spray were purchased from Vikash chemicals, Chennai, Tamil nadu, India. 2.2

Extraction of α-cellulosic micro filler Stage I: The water-retting process is used to extract the fibers from the peduncle. The

extracted fibers are dried under sunlight for nearly two days. The process of extracting fibers from CAPs is shown in Fig.1(a). Around 120–150 g of fibers was obtained from each 6

Journal Pre-proof peduncle by this retting process. Stage II: In this stage, fibers were finely chopped (nearly 1-2 mm) by using a high-speed flour mill for 30 min. Then, these chopped fibers are processed at different stages by means of prechemical treatment as shown in Fig.1(b).

The de-waxed process was carried out with

toluene-ethanol (2:1, v/v) solutions, by maintaining at a temperature of 70 °C for 240 min in a Soxhlet apparatus. The de-waxed CAP fibers were delignified with 0.7 wt.% sodium

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chlorite in an acidic solution (pH 4–4.2 adjusted by 10 wt.% acetic acid) and were maintained

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at a temperature of 100 °C for 120 min with liquor to CAP fibers ratio of 50:1 (g/g). The pH

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value was measured by using the digital pH meter with a glass probe (S202, suntornics,

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India). Then, the extracted holo-cellulose was washed with 2% sodium bisulfite and deionized water until the neutral pH value was reached. Further, it was treated with 17.5 %

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(wt./v) sodium hydroxide solution at a room temperature (30°C) for 60 min. The filtrate was

°C for nearly two hours.

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extensively washed with 10 wt.% acetic acid, distilled water and then dried in an oven at 110

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Acid hydrolysis was carried out with a volume concentration in the ratio of 10:1 from composition of 80% acetic acid and 70% nitric acid, and fiber respectively. Then, they are stirred vigorously for 30 min at a constant temperature of 120°C by using a high-speed mechanical stirrer with a speed of 1200 rpm. The ratio of the α-cellulose to liquor was 5:100 (wt.%). The acid hydrolysis reaction was quenched by adding the surplus amount of cold water (12°C) to the reaction mixture. The quenched suspension was washed sequentially with 95 wt.% of ethanol and distilled water for several times until it reached the neutralized pH value (7) as shown in Fig.1(c). The obtained α-cellulosic micro filler was oven-dried at 95°C for 5 hrs and then stored in a container at a room temperature of 30°C as shown in Fig.1(c). [Figure 1 should here] 7

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2.3

Preparation of composites Epoxy composites were prepared with different loading (0 wt.%, 3 wt.%, 6

wt.%, 9 wt.%, 12 wt.%, 15 wt.%, and 18 wt.%) of α-cellulosic micro filler based on epoxy resin weight. For this process, a predetermined amount of α-cellulosic micro filler was mixed with epoxy resin and stirred continuously for 20 min at room temperature (30°C) by using a high-speed mechanical stirrer to achieve a homogeneous mixture.

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Then, the calculated amount of hardener was added into the mixture (10:1 (epoxy

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g/hardener g)) and the mixture was further stirred for 30 min. The well-dispersed state

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of α-cellulosic micro filler in epoxy suspension was observed as shown in Fig.2 (a).

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Finally, the obtained mixture was poured into the mold size of 300 mm× 300 mm × 3 mm. Silicone spray was used inside the surface of the mold to facilitate easy removal of

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the composite samples. The closed mold was loaded into a compression-molding

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machine and then it allowed 24 hrs for resin curing at a pressure of 17MPa with a constant temperature of 80°C.

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After 24 hrs, the semi cured (flexible in nature) epoxy composites (Fig.2 (c)) were taken out from the mold as shown in Fig. 2(c). Afterwards, the composites were placed in between two metal plates (Fig.2 (d)) and were compressed at a constant load of 450N for 15days under atmospheric room temperature (30°C). Finally, full solid composite plates were obtained as shown in Fig.2.(e). [Figure 2 should here] 2.4

Material characterization

2.4.1 Characterization of α-cellulosic micro filler In the previous work, a chemically extracted (chlorination, alkaline and acid hydrolysis) α-cellulosic micro filler from Cocos nucifera var Aurantiaca peduncle was 8

Journal Pre-proof examined [31]. Due to an increase of solid α- cellulose content, the α-cellulosic micro filler has high thermal stability and cellulose crystalline index. In addition, it forms a micro cellulosic crystalline structure with high-order α- cellulose crystalline regions and low-order amorphous regions during the chemical treatment. Physicochemical and thermal properties of α-cellulosic micro filler were compared with raw Cocos nucifera var Aurantiaca Peduncle fiber as shown in table .1. In our proposed study, the α-

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cellulosic micro particles are used as filler reinforcement material in epoxy matrix.

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[Table 1 should here]

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2.4.1 FE-SEM analysis

The structure and morphology of chemically extracted α-cellulosic micro filler were

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investigated through FE-SEM analysis. Before the FE-SEM analysis, a 10µl drop of the

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dilute suspension of α-cellulosic micro filler was poured on a scientific micro slide (10mm x 10mm) and then dried under a table lamp for 3 hours.

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2.4.2 Mechanical properties of composites

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An average of five specimens for pristine epoxy and with different α-cellulosic micro filler reinforced epoxy composites as a function of filler loading (wt.%) were tested for each mechanical characteristic. The rectangular samples were cut by using diamond wheel cutter as per ASTM dimensions for studying the properties such as tensile, flexural, impact and dynamic mechanical tests. Before the test, the specimens were subjected to edge finishing process by applying emery sheet. 2.4.2.1 Tensile properties The tensile properties of the pristine epoxy and α-cellulosic micro filler reinforced epoxy composites as a function of filler loading (wt.%) were conducted based on the ASTM: D638-10 (165 mm long × 10 mm wide × 3 mm thick) by using an Instron 9

Journal Pre-proof 5500R digitalized universal testing machine. The tensile test was carried out at the rate of a crosshead speed of 5 mm/min [17]. 2.4.2.2 Flexural properties Flexural testing was carried out in the Instron 5500R digitalized universal testing machine with a crosshead speed of 1.2 mm/min, as per ASTM standards. Flexural test specimens were cut from the prepared composite plates as per the ASTM: D638-10 (165 mm long × 10 mm wide × 3 mm thick) [15].

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2.4.2.3 Impact properties

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The un-notched Charpy impact test was done on a digitized impact tester (Tinius

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Olsen model IT 503) according to ASTM: D256-10 (63.5 long×12.7 wide×3mm thick).

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Appropriate pendulum hammers were mounted at a speed of 10KJ for impact test [17]. 2.4.2.4 Fractography study

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The fractography study for the fractured tensile, flexural and impact specimens

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were investigated through FE-SEM analysis. Prior to a surface morphology visualization, the fractured samples with dimensions of 10mm x 10mm were fixed on the

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brass stub and were sputtered with gold in order to make the sample conductive, and the photographs were taken with a magnification level of 250×. 2.4.2.5 Dynamic Mechanical Analysis The visco-elastic behaviour of pristine epoxy and α-cellulosic micro filler reinforced epoxy composites were analyzed by using DMA Q 800 instrument according to the ASTM: D4065-01 (65 mm × 12 mm × 3 mm) [33]. The analysis was carried out with an oscillation frequency of 1 Hz with three-point bending mode in the temperature range of 30°C to 250°C. The sinusoidal strain with a heating rate of 5°C/min was maintained throughout the test. 2.4.2.6 FT-IR analysis 10

Journal Pre-proof The functional groups of pristine epoxy and α-cellulosic micro filler reinforced epoxy composites were analyzed by using iTR-ATR Nicolet iS10 FTIR spectrometer. The powdered samples were mixed with potassium bromide (KBr) separately. The transmittance spectra for various samples were recorded in the range from 4000 cm−1 to 500 cm−1 with a scan rate of 32 scans per minute at a resolution of 4 cm−1. 2.4.2.7 TGA analysis Thermal stability of pristine epoxy and α-cellulosic micro filler reinforced epoxy

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composites was characterized by using thermo gravimetric analyzer (Model STA 449

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F3, NETZSCH, Germany).This analysis was carried out at a heating rate of 10°C/min

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under a nitrogen atmosphere (20ml/min) from room temperature to 720°C.

Surface morphology of the α-cellulosic micro filler

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3.1

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3. Results and discussion

[Figure 3 should here]

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The FE-SEM image of chemically extracted α-cellulosic micro filler is shown in

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Fig.3. The fibers were fragmented into a single micro-sized fiber in the diameter range of 1532 µm during chemical treatment as shown in Fig 2. This resulted by the dissolution of noncellulosic plant components in CAP fibers during the sodium hypochlorite bleaching and alkali treatment [28]. After the acid hydrolysis treatment, there was a non-uniformity of micro-fibrils with rough surface due to the occurrence of hydrolytically calved the glycosidic bonds of cellulose. It provided a better aspect ratio, which may induce a strong interfacial interaction between the α-cellulosic micro filler and the polymer matrix. The yield of αcellulosic micro filler extracted from the dried CAP fibers was found to be 65%.

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Journal Pre-proof 3.2 Tensile properties The tensile properties of the pristine epoxy and α-cellulosic micro filler reinforced epoxy composites as a function of filler loading (wt.%) are shown in Fig.4 (a-b). In this study, the pristine epoxy is recorded with the tensile strength and tensile modulus being 32.5 ± 1.5 MPa and 2.74 ± 0.07 GPa respectively. With the increase of α-cellulosic micro filler loading (wt.% ) into the epoxy matrix, the tensile strength of the epoxy composite increased up to the optimum loading of α-cellulosic micro filler (15 wt.%) as shown in Fig.4 (a). It was

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evident that 3wt.% and 6 wt.% of α-cellulosic filler reinforced composites produces a tensile

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strength of 1.05 and 1.16 times higher than that of pristine epoxy, respectively. Similarly,

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when the α-cellulosic micro filler loading was increased from 9 wt.% to 12 wt.%, the tensile

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strength increased linearly from 42.2 ± 1.2 MPa to 46.4 ± 1.4 MPa, respectively. The maximum tensile strength of 52.5 ± 1.8 MPa was obtained for15wt.% of α-cellulosic

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micro filler reinforced epoxy composite, due to the better dispersion of α-cellulosic micro

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filler. It provides good interfacial adhesion properties between the epoxy and α-cellulosic micro filler, thereby allowing a better transfer of the applied longitudinal stress during tensile

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test. At the same time, the maximum tensile strength for15 wt.% of α-cellulosic micro filler reinforced epoxy composites increased by nearly 60.9% when compared to pristine epoxy. When the α-cellulosic micro filler loading exceeded by15 wt.%, the tensile strength decreased due to the agglomeration of α-cellulosic micro filler and was surrounded by an insufficient amount of resin in the composite. This is not suitable for any applications because there is a reduction in stress transfer between the α -cellulosic micro filler and the matrix. The tensile strength for15 wt.% is (52.5 ± 1.8MPa ) of α-cellulosic micro filler reinforced epoxy composites is higher than that of the other cellulosic filler reinforced polymer composites such as date seed reinforced vinyl ester composite (40.3 MPa), robusta 12

Journal Pre-proof reinforced polyester composite (15 MPa), arundo donax reinforced Epoxy composite (48 MPa), coir reinforced Polyester composite (45.63 MPa), wood apple reinforced epoxy composite (43.6 MPa), coconut shell reinforced epoxy composite (41.3 MPa), tamarind seed reinforced vinyl ester composite (34.1 MPa), wood flour/pulp reinforced Polyvinyl chloride composite (17 MPa), oil palm shell reinforced Polyester composite (41 MPa), sawdust reinforced polypropylene composite (30 MPa), Pine needles reinforced resorcinol formaldehyde composite (16.5 MPa), jatropha curcas L reinforced epoxy composite (33.83

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MPa) and lower than that walnut reinforced Epoxy composite (163 MPa), commercial

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cellulose filler with alkali-treated hemp fiber reinforced epoxy composite (52.92 MPa), bio

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char reinforced Polyester composite (60 MPa) [16,36,9,32,34,15,10,33,38,13,14,35,37,8].

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[Figure 4 should here] [Table 2 should here]

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The stress-strain curve for pristine epoxy and 15wt.% of α-cellulosic micro filler

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loading epoxy composites are shown in Fig. 4(b). The tensile modulus for the composites with different loading of α-cellulosic micro filler was calculated from the linear behaviour of

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the stress-strain curve. The tensile modulus (GPa) is used to measure the stiffness of the composites, which increased with the concentration of α-cellulosic micro filler in the epoxy matrix up to the optimum level and then decreased due to an insufficient bonding between the α-cellulosic micro filler and the matrix. The tensile modulus of the pristine with different loading of α-cellulosic micro filler reinforced epoxy is shown in Fig.4(c). Due to the addition of α-cellulosic micro filler from 3 wt.% to 15 wt.%, the modulus enhanced from 2.76±0.02GPa to 3.3±0.06GPa. The maximum tensile modulus of 3.3±0.06 GPa was attained for15 wt.% of α-cellulosic micro filler reinforced epoxy composite because the α-fillers were well dispersed into the epoxy matrix. Further, with the increase of α-cellulosic micro filler content into the epoxy matrix, 13

Journal Pre-proof the tensile modulus decreased slightly due to the occurrence of agglomeration which provides a poor interaction of α-cellulosic micro filler with the epoxy matrix. Elongation at break indicates the percentage of strain that can be experienced before rupture in tensile testing. The percentage of elongation at break (Fig.4 (d)) between 3 wt.% and 15 wt.% is ranged from 0.68% to 0.98 %. The elongation at rupture for15 wt.% of α-cellulosic micro filler reinforced epoxy composite was less than that of the pristine epoxy. The decrease in elongation of α-cellulosic micro filler reinforced epoxy composites occured due to an

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increase in the rigidness of the epoxy composites. The results of tensile strength of α -

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cellulosic micro filler reinforced epoxy composites were compared with that of the other

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previously published organic filler reinforced polymer composites. Subsequently, randomly

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3.2 Flexural properties

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oriented natural fibers reinforced polymer composite are presented in Table 2.

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The flexural strength and modulus for the pristine epoxy and α-cellulosic micro filler reinforced epoxy composites as a function of filler loading (wt.%) are shown in Fig.5 (a-b).

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In this study, the flexural strength and flexural modulus were recorded as 82.5 ± 0.8MPa and 2.5±0.2GPa, respectively. At the same time, the flexural strength for 3, 6, 9, 12, and 15 wt.% of α-cellulosic micro filler reinforced epoxy composites are 96.2 ± 1.2 MPa,104 ± 0.8,119 ± 0.8MPa, 125 ± 1.1 MPa and 135±0.8 MPa respectively. As a result, there is an increase in proportion by nearly 16.7%,26%, 43.2%, 51.5% and 63.3 % respectively, when compared to pristine epoxy. Fig.5(a) indicates the flexural strength being increased with the filler content up to 15 wt.% while it is maximum (135 ± 0.8 MPa) for15wt.% of α-cellulosic micro filler loading into the epoxy composite. If the α-cellulosic micro fillers are homogeneously dispersed in epoxy matrices, it provides more resistance during the shear stress transfer to composites in 14

Journal Pre-proof addition to effectively transmitting the bending stress through the interface. Similar observations of remarkable improvements are noted even in the properties such as flexural strength and modulus. Similar improvements due to the incorporation of α-cellulosic micro filler in epoxy composite, were also noticed earlier [39]. However, when the α-cellulosic micro filler increased to 18wt. %, the aggregation of the α-cellulosic micro filler too increased and the reinforcement reduced due to the formation of cluster and voids in the interfacial regions of the epoxy matrix. This finding is in concurrence with the previous

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studies, which have lower mechanical properties due to the agglomeration of α-cellulosic

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micro filler during higher loading of fillers in the polymer matrix [39].

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[Figure 5 should here]

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The flexural strength (135±0.8 MPa) for 15 wt.% of α-cellulosic micro filler reinforced epoxy composites is higher than that of other cellulosic filler reinforced polymer

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composites such as robusta reinforced Polyester composite (26MPa),arundo donax reinforced

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Epoxy composite (88 MPa), wood apple reinforced Epoxy composite(78.19 MPa), coconut shell reinforced epoxy composite(68.25 MPa), tamarind seed reinforced vinyl ester composite

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(121 MPa), wood flour/pulp reinforced Polyvinyl chloride composite (42 MPa), oil palm shell reinforced Polyester composite (62 MPa), sawdust reinforced Polypropylene composite (54 MPa), pine needles reinforced Resorcinol formaldehyde composite (7.26 MPa), hazelnut reinforced Epoxy composite (117 MPa) and lower than that walnut reinforced epoxy composite (1360 MPa), date seed reinforced vinyl ester composite (149MPa), commercial cellulose filler with alkali-treated hemp fiber reinforced epoxy composite (170 MPa) and coir reinforced Polyester composite (160MPa) [36,9,10,34,10,33,38,13,40,35,37,32]. The results of flexural strength of α -cellulosic micro filler reinforced epoxy composites were compared with that of the other previously published organic filler reinforced polymer composites. Randomly oriented natural fibers reinforced polymer composite are presented in table 2. 15

Journal Pre-proof The flexural modulus of the composites with different wt.% of α-cellulosic micro filler reinforced epoxy composites are illustrated in Fig. 5(b). From the figure it is evident that the flexural modulus also have a similar behaviour like tensile modulus as shown in Fig.4(a). With the addition of α-cellulosic micro filler from 3 wt.% to 15 wt.%, the flexural modulus increased from 3.2 ± 0.05 GPa to4.78 ± 0.02 GPa. The maximum flexural modulus of 4.78 ± 0.02 GPa was attained for15 wt.% of α-cellulosic micro filler reinforced epoxy composite. Consequently, 15 wt.% of α-cellulosic micro filler reinforced epoxy composites

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can withstand more loads as it exhibits a higher value of flexural strength and modulus,

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among the rest of the composites.

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3.3 Impact properties

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The specimens of α-cellulosic micro filler epoxy composites, which were fabricated with various filler wt.%, were tested for impact strength. Fig. 6 shows the results of impact

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strength for the α-cellulosic micro filler epoxy composites as a function of filler loading

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(wt.%). The impact strengths of 3, 6, 9, 12, and 15 wt.% of α-cellulosic micro filler reinforced epoxy composites are 9.4 ± 0.6 KJ/m2, 9.8 ± 0.75 KJ/m2, 11 ± 0.8 KJ/m2, 12.1 ±

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0.7 KJ/m2 and 12.8 ± 0.7 KJ/m2 respectively. At 9 wt.% filler, the improvement on impact strength was 19.5% higher than that of pristine epoxy. Meanwhile, when it was increased from 3 wt.% to 15 wt.%, the impact strength slightly increased from 9.4 ± 0.6 KJ/m2 to 12.8 ± 0.7 KJ/m2, respectively. The maximum impact strength for15 wt.% of α-cellulosic micro filler reinforced epoxy composite was 12.8 ± 0.7 KJ/m2, which is chosen as an optimum value. In addition, it was 39% higher than that of pristine epoxy. Hence, this observation provides an excellent interfacial bond between the filler and the epoxy matrix, and the fillers are homogenously dispersed strongly to enhance the load tearing capacity of the composites. So, propagation of crack was prevented and the energy was easily absorbed, thereby improving the impact strength. A similar observation can be 16

Journal Pre-proof noticed earlier in the previous literature [15]. In general, the impact strength of the micro filler reinforced polymer composites have been rarely studied in the literature. When the α -cellulosic micro filler loading exceeds to15 wt.%, the impact strength decreased, as shown in Fig.6. The insufficient amount of epoxy matrix to disperse well into the α-cellulosic micro filler and aggregation of α-cellulosic micro filler reduces the impact properties of the composite accordingly. This impact strength (12.8 ± 0.7 KJ/m2) for15 wt.% of α-cellulosic micro filler reinforced epoxy composites was closely related to other

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cellulosic filler reinforced polymer composites such as biochar reinforced polyester

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composite (10 KJ/m2 ), tamarind seed reinforced vinyl ester composite (14 KJ/m2) [8,15].

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The results of impact strength of α -cellulosic micro filler reinforced epoxy composites were

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compared with that of other previously published organic filler reinforced polymer composites. Randomly oriented natural fibers reinforced polymer composite are presented in

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table 2.

3.4 Fractography study

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[Figure 6 should here]

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The fractured tensile specimens are shown in Fig.7 (a-b). The huge amount of smooth and glassy exterior wavy surface or stream like surface (denoted as B), matrix cracks (denoted as C), and very little amount of irregular jig-jagged surface (denoted as A), are identified in the tensile fracture specimen as shown in Fig. 7 (a). It clearly indicates the brittle mode of fracture happened during the tensile test and this was due to presence of very less amount of α-cellulosic micro filler in epoxy matrix. From Fig.7(b), it can be observed that there are a large number of irregular and jagged pattern (denoted as A), a very few numbers of glassy exterior wavy or stream - like pattern (denoted as B) and the existence of matrix cracks (denoted as C) in the fractured surface (15 wt% of α-cellulosic micro filler reinforced epoxy composite). The irregular and 17

Journal Pre-proof jagged pattern indicate a better dispersion of α-cellulosic micro filler which provides an excellent interfacial adhesion property between the α-cellulosic micro filler and the epoxy, thereby allowing a better transfer of the applied stress during the test. Similar behaviour was observed in the tested specimen also, which is already taken during flexural and impact tests as shown in Figure.7 (c-f). The nature of fractured specimens for 15 wt.% and 3 wt.% of αcellulosic micro filler reinforced epoxy composite is illustrated in Table.3. Among the different wt.% epoxy composites, 15 wt.% α-cellulosic micro filler

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reinforced epoxy composite exhibits the superior mechanical properties compared to others.

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Hence, this (15 wt.%) α-cellulosic micro filler reinforced epoxy composites is chosen as

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optimized one, which were used for the DMA, FT-IR, and TGA analysis and the results were

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compared with pristine epoxy.

[Table 3 should here]

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[Figure 7 should here]

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3.5 Dynamic Mechanical Analysis

For polymers, the glass transition temperature or secondary transition and yield

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transition is very essential for dynamic conditions with a wide range of temperatures, which is applied to polymers. The storage modulus and loss modulus of pristine epoxy and 15 wt.% of α-cellulosic micro filler reinforced epoxy composite were investigated through dynamic mechanical analysis and its curve is displayed in Fig.8 (a-b). There is occurrence of loss in storage modulus, due to an increase of temperature for the sample of pristine epoxy and 15 wt.% of α-cellulosic micro filler reinforced epoxy composite. This loss could be noticed in three stages namely glass region, transition region, and rubbery region which are illustrated in Fig.8(a). From the figure, it can be observed that 15 wt.% of α-cellulosic micro filler reinforced epoxy composite shows an enhancement in storage modulus (E’) value than pristine epoxy during every stage. The storage modulus for 15 wt.% of α-cellulosic micro 18

Journal Pre-proof filler reinforced epoxy composite is 26% higher than that of pristine epoxy at room temperature (30°C) due to the presence of stiffer α-cellulosic micro filler as shown in Fig.8(a). This has already been confirmed in Section 3.2 under discussion on tensile testing. During the first stage (below the glass transition temperature), there occurs a very slow mobility of polymer chains in the solid epoxy matrix around the α-cellulosic micro filler. This results with a gradual drop in the storage modulus, which normally occurs at the temperature range of 30°C – 80°C. Figure 8 (a), indicates an increase in E’ with a filler

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loading of α-cellulosic micro filler as the interface is stronger between the α-cellulosic micro

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filler with high elastic modulus and the matrix. In the second stage (transition stage), the

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storage modulus rapidly decreased due to the higher segmental movement of polymer chains

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occurring at the temperature regions of 80°C – 98°C [32]. In this stage, the stiffness of the pristine epoxy and 15 wt.% of α-cellulosic micro filler reinforced epoxy composite dropped

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dramatically with an increase in viscosity of the epoxy and consequently there is a drop-in

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storage modulus which is maximum. The pristine epoxy and the composites are physically soft because there is a drop-in storage modulus with the rise of temperature. Finally, the

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behaviour was rubbery when the temperature exceeds 98°C. Loss modulus is regarded as a vicious response of the materials and it can be measured in terms of energy loss under deformation as heat/cycle [41]. The loss modulus curve for 15 wt.% of α-cellulosic micro filler reinforced epoxy composite and pristine epoxy is shown in Fig.8(b). The glass transition temperature for 15 wt.% of α-cellulosic micro filler reinforced epoxy composite is shifted towards the higher temperature which is primarily attributed to the segmental immobilization of the matrix at the α-cellulosic micro filler surface. The transition region is higher than that of pristine epoxy, which may be due to better dispersion and there is no visibility of agglomeration in the composite of α-cellulosic micro filler. The loss modulus curve is spread over a wider range with a higher peak due to the 19

Journal Pre-proof presence of α-cellulosic micro filler in the epoxy matrix. In the previous literature, a similar observation was found in the cellulosic filler reinforced polymer composite [32,41, 42]. From Fig.8(c), it is revealed that the 15 wt.% of α-cellulosic micro filler reinforced epoxy composite exhibits the least damping factor during the transition region in comparison with pristine epoxy. This is due to the existence of higher elastic modulus in α-cellulosic micro filler that carries a greater amount of load and it produces a lesser amount of strain at the interface region during testing. Therefore, the composite has more potential to store the load

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instead of dissipating it, due to good interfacial adhesion between the α-cellulosic micro filler

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and the epoxy. The damping factor is also significantly increased with temperature and

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attains the uppermost value at the end of the transition stage. Afterwards, it decreases in

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which a similar behaviour is observed in the loss modulus curve [41].

3.6 FT-IR analysis

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[Figure 8 should here]

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The mechanism of inter polymer miscibility through hydrogen bonding and is well regarded as a molecular fingerprint of the pristine epoxy and 15wt.% of α-cellulosic micro

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filler reinforced epoxy composite which is examined through Fourier transform infrared spectroscopy as shown in Fig. 9. The wideband appearing at around 3100-3600 cm−1 corresponds to N-H stretching of the primary and secondary amine of hardener and O-H stretching vibration of the hydroxyl group is observed in pristine epoxy. Incorporation of αcellulosic micro filler into the epoxy matrix produced a doublet, which was mainly due to the un-reacted primary amine groups. The peak at wave number 3040 cm−1 refers to the C-H stretching of the terminal oxirane group of epoxy resin. The intensity peaks at 2900cm-1 and 2850 cm-1 indicated the presence of C-H stretching in epoxy resin. The peak was observed at 1100cm-1 and 1050cm-1 due to the presence of C-O of saturated aliphatic primary alcohols [43]. After the addition of α-cellulosic micro filler in the epoxy matrix, the peaks decreased 20

Journal Pre-proof significantly as shown in Fig.9. The peak at 2305cm-1 refers to the double CO2 band, which is found in the pristine epoxy and α-cellulosic micro filler in the epoxy matrix [44]. The peak at wave number 1505 cm−1 refers to the N-H deformation of the primary amine of hardener. The peak at wave number 1602cm-1 and 1450cm-1 indicate the characteristics of DGEBA epoxy resin which resulted due to the presence of aromatic ring stretching of C=C in both the samples as shown in Fig.9. The sharp peak at 1240cm-1 indicates the stretching of epoxide–

O–C of the terminal oxirane group of the epoxy system.

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C–O bonds [44]. The visible sharp peak observed at 820cm-1 indicates the stretching of C–

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[Figure 9 should here]

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3.7 Thermo gravimetric Analysis

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The thermo gravimetric analyses for the pristine epoxy and 15 wt.% of the αcellulosic micro filler reinforced epoxy composites are shown in Fig.10(a-b). The initial

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weight loss of 2 wt.% occurred up to 120°C, due to evaporation of physically weak moisture.

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This is loosely bounded on the surface of the composite and dehydration of secondary

pristine epoxy.

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alcoholic groups for 15 wt.% of α-cellulosic micro filler reinforced epoxy composite and

The decomposition and pyrolysis of aromatic groups for the epoxy network, which effects the reduction in curing agent of aliphatic amine owing to break the C–N bond with low energy, took place during the second stage of thermal degradation up to 290°C[45,46]. At this stage, a very negligible weight loss was found at around 2% for 15 wt.% of αcellulosic micro filler reinforced in epoxy composite and pristine epoxy. The occurrence of major degradation could be due to the decomposition of the epoxy network, with a weight loss of about 65% to 74% between the temperature regions of 290°C and 350°C for pristine epoxy and, 290°C and 372°C for 15 wt.% epoxy reinforced composite respectively. From the TGA and DTG graph (Fig.10.(a-b)), the thermal stability and thermal degradation of the 21

Journal Pre-proof pristine epoxy were found to be 290°C and 350°C, while the thermal stability and thermal degradation values for 15 wt.% of α-cellulosic micro filler reinforced epoxy composites are 290 °C and 365°C respectively. Thus, the thermal stability and thermal degradation of the composite were shifted to a higher temperature due to the formation of carbon char content in α-cellulosic micro filler reinforced epoxy composite and it acts as an insulating layer against further thermal degradation of the composite. [Figure 10 should here]

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4. Conclusions

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The α-cellulosic micro fillers were extracted from Cocos nucifera var Aurantiaca

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Peduncle through the chemical treatment process. A huge amount of α- cellulosic micro

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filler (65 wt.%), extracted from this peduncle is more advantageous and it can be utilized as a reinforcement in polymer composites. The α- cellulosic micro-filler with a

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short cylindrical structure , converging from the size of a macro scale is confirmed from

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the analysis of FE-SEM. The preparation of epoxy composites with different αcellulosic micro filler loadings has been successfully carried out by using a compression

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molding technique. The mechanical properties such as tensile, flexural and impact strength have significantly improved for 15 wt.% of α-cellulosic micro filler reinforced in the epoxy matrix when compared with those of other wt.% of α-cellulosic micro filler loading. FE-SEM analysis confirmed that there is a minimal fracture in the matrix and glassy exterior wavy or stream like pattern in the 15 wt.% of α-cellulosic micro filler reinforced epoxy composite. The reinforcement of α-cellulosic micro filler with a higher interfacial surface area causes a strong interaction between the homogeneously dispersed α- cellulosic micro filler and the epoxy matrix. The results which are obtained from DMA and TGA indicate that the storage modulus, loss modulus, thermal stability, and thermal degradation temperature increased for 15 wt.% of α-cellulosic micro filler 22

Journal Pre-proof reinforced epoxy composite while compared with pristine epoxy. Thus mechanical and thermal properties of α-cellulosic fillers reinforced epoxy composites show excellent figures than other micro filler reinforced composite materials, giving scope to extend the application in building, and automotive products industries.

Acknowledgment The author is grateful for the support rendered by the Management of K.L.N. College of

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Engineering.

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47. Nagarajan

characterization of alkali treated cocos nucifera var aurantiaca peduncle fibers reinforced

epoxy

composites.

Materials

15;6(12):125310.

27

Research

Express.

2019

Nov

Journal Pre-proof

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Physicochemical and thermal properties of α-cellulosic micro filler

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Table.1

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Table Captions

Comparison of the mechanical (tensile, flexural and impact) properties of α-

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Table.2

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compared with raw Cocos nucifera var Aurantiaca Peduncle fiber.

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cellulosic filler reinforced epoxy composite with other cellulosic filler

Table.3

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reinforced polymer composites and short fiber composite. Nature of fractured specimens of 15 wt.% and 3 wt.% of α -cellulosic micro filler reinforced epoxy composite

Figure Captions Fig.1.

(a). extraction process of the CAPFs from peduncle

(b). pre-chemical

treatment process of the CAPFs (c). isolation of α -cellulosic micro filler Fig.2

(a). Well-dispersed state of α -cellulosic micro filler in epoxy suspension (b). hydraulic press (c). Post curing process (d). prepared composites

Fig.3.

FE-SEM image of extracted α -cellulosic micro filler 28

Journal Pre-proof Fig.4.

tensile strength (b). Stress-strain curve (c). tensile modulus (d). elongation at break of the pristine epoxy and α-cellulosic micro filler reinforced epoxy composites as a function of filler loading (wt.%)

Fig.5.

(a). flexural strength (b). flexural modulus of the pristine epoxy and αcellulosic micro filler reinforced epoxy composites as a function of filler loading (wt.%) impact strength of the pristine epoxy and α-cellulosic micro filler reinforced

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Fig.6.

epoxy composites as a function of filler loading (wt.%) FE-SEM image of (a). tensile fractured specimen (3 wt.% α -cellulosic micro

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Fig.7.

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filler loading) (b). tensile fractured specimen (15 wt.% α -cellulosic micro

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filler loading) (c). flexural fractured specimen (3wt.% α -cellulosic micro filler

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loading) (d). flexural fractured specimen (15 wt.% α -cellulosic micro filler loading) (e). impact fractured specimen (3 wt.% α -cellulosic micro filler

Fig.8.

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loading)

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loading) (f). impact fractured specimen (15 wt.% α -cellulosic micro filler

(a).storage modulus (b). loss modulus (c). mechanical loss factor curve of the 15 wt.% of α-cellulosic micro filler reinforced epoxy composite and pristine epoxy

Fig.9.

FT-IR spectra of the 15 wt.% of α -cellulosic micro filler reinforced epoxy composite and pristine epoxy

Fig.10.

(a).TGA curve and (b). DTG curve of the 15 wt.% of α -cellulosic micro filler reinforced epoxy composite and pristine epoxy

29

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Journal Pre-proof Table 1 : Physicochemical and thermal properties of α-cellulosic micro filler compared with raw Cocosnucifera var Aurantiaca Peduncle fiber S.No

Nature of fiber

αcellulose

Hemicellulose Lignin (wt.%)

Wax

(wt.%) (wt.%)

Crystalline Cellulose index (%)

1.

Extracted α-

87.5

size (nm)

1.2

2.8

l a

filler Raw Cocosnucifera var Aurantiaca

40.5

18.2

rn

u o

e

----

cellulosic micro

2.

f o

crystalline stability

o r p

(wt.%)

15.9

76.1%

r P

Thermal Thermal

6.87

Reference

degradation

(°C )

(°C)

257

354

[31] 3.5

50.2%

J

Peduncle fiber

31

5.8

250

350

Journal Pre-proof

Table 2: Comparison of the mechanical (tensile, flexural and impact) properties of α-cellulosic filler reinforced epoxy composite with other

f o

cellulosic filler reinforced polymer composites and short fiber composite. S.No Filler

Size

Composite

p e

Flexural

Impact

strength

strength

strength

matrix

(MPa)

(MPa)

(KJ/m2)

n r u

epoxy

52.5±1.8

125±1.2

14.6±0.6

-

Hand layup

epoxy

52.92

170

30 – 60

Compression

Vinyl ester

40.3

149

process

α-

Name of the

(µm/nm) manufacturing polymer

type

1.

Cocos nucifera var

cellulosic Aurantiaca Peduncle 2.

Commercial cellulose

3.

Date seed

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Tensile

Filler name

15-32

o J

l a

r P

Compression

µm

Reference

Present study

µm

32

0.85

[36] [14]

Journal Pre-proof 4.

Robusta

5-10 µm

Hand layup

Polyester

15

26

-

[34]

5.

Arundo donax

150 µm

Hand layup

Epoxy

48

88

-

[6]

45.63

160

-

[13]

43.6

78.19

-

[16]

e

Epoxy

41.3

68.25

-

[16]

n r u 16.3-

- 2 mm 6.

Coir

250 nm

Compression

Polyester

7.

Wood apple

212 nm

Hand layup

Epoxy

to 1 mm 8.

9.

10.

212 nm

Coconut shell

Tamarind seed

Lignocellulosic

Wood flour/pulp

o J

r P

Hand layup

f o

o r p

to 1 mm

l a

25–60

Compression

Vinyl ester

34.1

121

14

[12]

Injection

Polyvinyl

17

42

-

[7]

μm

18.6 μm

chloride

33

Journal Pre-proof 11.

50 μm -

Oil palm shell

Hand layup

Polyester

41

62

54

-

[15]

1.18mm 12.

Saw dust

----

Injection

Polypropylene 30

13.

Bio-char

45 nm-

Compression

Polyester

Pine needles

200 µm

Compression

e

Resorcinol

r P

-

10

[5]

16.5

7.26

-

[10]

o r p

510 nm 14.

f o

60

[36]

formaldehye

15.

Compression

n r u

Epoxy

30

117

-

[19]

µm

l a

----

Hand layup

Epoxy

163

1360

-

[17]

575±265 Hand layup

Epoxy

33.83

-

-

[11]

200-300

Hazelnut

16.

Walnut

17.

Jatropha curcas L

o J

µm

34

Journal Pre-proof 18.

Short

Cocos nucifera var

fibers

Aurantiaca Peduncle

---

Compression

Epoxy

57.5±5.2

130.2±6.1

15.25±0.5

56.21

---

137.05

9.44

40.8

65.9

---

e

16.39

57.53

---

Epoxy

8.37

40.48

5.8

19.

Nappier grass (20 wt.%)

---

Hand layup

Epoxy

28.45

20.

Phoenix.sp

---

Compression

Epoxy

39.22

21.

Arundo donex

---

Hand layup

Epoxy

22.

Banana

----

Hand layup

23.

sisal

---

l a

r P

Hand layup

n r u

o J

35

Epoxy

f o

o r p

[47]

Journal Pre-proof Table.3: Nature of fractured specimens of 15 wt.% and 3 wt.% of α -cellulosic micro filler reinforced epoxy composite irregular

glassy exterior matrix

S.No

and jagged

wavy or stream

pattern

like pattern

(A)

(B)

Less

High

High

Less

Less

Less

High

High

High

Less

Less

Less

High

High

High

Less

Less

Fractured specimen

fracture (C)

1.

ro

filler loading in epoxy)

of

Tensile ( 3 wt.% of α -cellulosic micro

Tensile ( 15wt.%ofα -cellulosic micro

High filler loading in epoxy)

re

Flexural ( 3wt.%ofα -cellulosic micro

-p

2.

3.

lP

filler loading in epoxy) Flexural ( 15wt.%ofα -cellulosic 4.

na

micro filler loading in epoxy)

5.

Jo ur

Impact ( 3wt.% of α -cellulosic micro filler loading in epoxy)

Impact ( 15wt.%ofα -cellulosic micro 6.

filler loading in epoxy)

36

-p

ro

of

Journal Pre-proof

Fig.1. (a). extraction process of the CAPFs from peduncle (b). pre-chemical treatment

Jo ur

na

lP

re

process of the CAPFs (c). isolation of α -cellulosic micro filler

Fig.2. (a). Well-dispersed state of α -cellulosic micro filler in epoxy suspension (b). hydraulic press (c). Post curing process (d). prepared composites

37

re

-p

ro

of

Journal Pre-proof

Jo ur

na

lP

Fig.3. FE-SEM image of extracted α -cellulosic micro filler

38

Jo ur

na

lP

re

-p

ro

of

Journal Pre-proof

39

Jo ur

na

lP

re

-p

ro

of

Journal Pre-proof

Fig.4. (a). tensile strength (b). stress-strain curve (c). tensile modulus (d). elongation at break of the pristine epoxy and α-cellulosic micro filler reinforced epoxy composites as a function of filler loading (wt.%)

40

Jo ur

na

lP

re

-p

ro

of

Journal Pre-proof

Fig.5. (a). flexural strength (b). flexural modulus of the pristine epoxy and α-cellulosic micro filler reinforced epoxy composites as a function of filler loading (wt.%)

41

lP

re

-p

ro

of

Journal Pre-proof

na

Fig.6. impact strength of the pristine epoxy and α-cellulosic micro filler reinforced

Jo ur

epoxy composites as a function of filler loading (wt.%)

42

Journal Pre-proof

(a)

na

(d)

Jo ur

(c)

lP

re

-p

ro

of

(b)

(f)

(e)

Fig.7.FE-SEM image of (a). tensile fractured specimen (3 wt.% α -cellulosic micro filler loading) (b). tensile fractured specimen (15 wt.% α -cellulosic micro filler loading) (c).

43

Journal Pre-proof flexural fractured specimen (3wt.% α -cellulosic micro filler loading) (d). flexural fractured specimen (15 wt.% α -cellulosic micro filler loading) (e). impact fractured specimen (3 wt.% α -cellulosic micro filler loading) (f). impact fractured specimen (15 wt.% α -cellulosic micro

Jo ur

na

lP

re

-p

ro

of

filler loading)

44

-p

ro

of

Journal Pre-proof

re

Fig.8. (a). storage modulus (b). loss modulus (c). mechanical loss factor curve of the 15

Jo ur

na

lP

wt.% of α-cellulosic micro filler reinforced epoxy composite and pristine epoxy

Fig.9. FT-IR spectra of the 15 wt.% of α -cellulosic micro filler reinforced epoxy composite and pristine epoxy

45

Jo ur

na

lP

re

-p

ro

of

Journal Pre-proof

Fig.10.a). TGA curve and (b). DTG curve of the 15 wt.% of α -cellulosic micro filler reinforced epoxy composite and pristine epoxy

46

Journal Pre-proof Authors Statement K.J.NAGARAJAN: Conceptualization; Investigation; Methodology

Jo ur

na

lP

re

-p

ro

of

A.N.. Balaji, K.Sathick basha, N.R.Ramanujam & R.Ashok Kumar: Validation; Writing – review & editing.

47