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Effects of flame retardants on the properties of particle boards prepared from cottonseed hulls
Biological Wastes 19 (1987) 197-203
Effects of Flame Retardants on the Properties of Particle Boards Prepared from Cottonseed Hulls S. N. P a n d e y & R. M. G u r j a r Cotton Technological Research Laboratory (ICAR), Adenwala Road, Matunga, Bombay-400019,India (Received 22 February 1986; accepted 29 May 1986)
A BS T R A C T The effects of fire retardants on the properties of particle boards made from cottonseed hulls were studied. The boards were treated with (1) 70% borax + 3 0 % boric acid (FR(1)); (2) 60% borax+25% boric acid+15% ammonium dihydrogen orthophosphate ( F R ( 2 ) ) and were evaluated for duration of flaming, after-glow, charred area, charred length and per cent loss in weight, along with physico-mechanical properties. Fire retardant properties, water resistance and per cent thickness swelling improved, and bending strength decreased, with increase in concentration of fire retardants. Treatment (2) wasfound to be the better fire retardant since it served the dual purposes of flame and glow retardation.
INTRODUCTION The annual production of cottonseed in India is about 3 million tonnes from which about 1"2 million tonnes of cottonseed hull, an outer covering of the seed, is available. Besides the use of cottonseed as a source of oil, cake and linters, the cottonseed hulls can also be used for various other purposes (Pandey, 1971). In addition to using hulls to produce xylose (Bass 8,s Olcott, 1940) and a highly effective activated carbon from hull bran, furfural (Peters, 1936) a very important chemical can be isolated, and the hull can also be used for the production of various types of good strength particle boards (Pandey & Gurjar, 1985). Cottonseed is a horny material which protects the seed kernel by an 197 Biological Wastes 0269-7483/87/$03.50 O ElsevierApplied SciencePublishers Ltd, England, 1987. Printed in Great Britain
198
s. N. Pandey, R. M. Gurjar
external hard brownish covering, chemically consisting of three major components--pentosans, cellulose and lignin (:~-cellulose, 45%-47%; pentosan, 25%-27% and lignin, 18%-20%). Considering fire as a hazard it is essential to protect buildings, furniture, etc., from fire. Fire-resistant materials such as polyammonium phosphate and aluminium sulphite, boric acid, borax and sodium silicate can be used to improve fire- and water-resistance properties of particle boards. The present work studied the effects of borax, boric acid and a m m o n i u m dihydrogen orthophosphate, mixed in different proportions and concentrations while preparing the particle board from cottonseed hull, on physical, mechanical and fire retardant properties.
METHODS
Hulls and analysis Mixed cottonseed hulls of different varieties were obtained from local expellers. Urea formaldehyde resin and a m m o n i u m chloride were used as binder and catalyst, respectively. Borax, boric acid and a m m o n i u m dihydrogen orthophosphate were used as fire retardant materials. Chemical analysis of the mixed hulls was carried out for holocellulose (Wise et al., 1946; Erickson, 1962), lignin, pentosans and ash according to T A P P I standards and suggested methods and the results are given in Table 1. Separate samples were used for each analysis. TABLE 1 Chemical Analysis of Cottonseed Hull (% dry weight) Ash Lignin Pentosan Holocellulose
2-74 31"5 18.5 64-7
Preparation of particle boards Cottonseed hull was ground to suitable size in a laboratory beater type mill. Urea formaldehyde resin solution (15%) as a binder and 3% (on resin) a m m o n i u m chloride as catalyst were sprayed on the ground material, which was treated with different solutions of known concentration of fire retarding materials. These were 70% borax + 30% boric acid; 60% borax
Flame retarding particle boards
199
+ 25% boric acid + 15% a m m o n i u m dihydrogen orthophosphate. The moisture content of the material was adjusted by drying before pressing. The material was framed into a false impression by cold pressing and then pressed between heated platens in a hydraulic press. In order to obtain the desired thickness, pressure, temperature and time were adjusted while pressing. The boards were prepared under pressure, 16 kg c m - 2 for 4 rain at a platen temperature of 150°C. The moisture in the material acted as plasticizer and the lignin as a binder which becomes soft at higher temperatures. The boards were then trimmed and kept for conditioning for dimensional stability before use. A control board was prepared as above from cotton hulls without binder and fire retardants. The prepared boards were tested for bending strength, density, water absorption after 2h and per cent thickness swelling as per ISI methods (Indian Standard Specification IS-2380, 1963). These boards were also tested for the fire retardant properties, duration of flaming, after-glow, charred length, charred area and per cent loss in weight by standard methods. The time of exposure of the specimen to fire was set to 5 min. The test methods are defined as follows. Duration offlaming--The period which elapses between the removal of the igniting flame and the time that the specimen ceases to flame, expressed in seconds. Time of glowing--The spread of after-glow, observed until it has ceased, expressed in seconds. RESULTS AND D I S C U S S I O N The control sample shown in Tables 2 and 3 is without binder and fire retardant, to avoid the interference in properties, while other samples contain 15% of binder and concentrations of fire retardant from 0% to 15%.
Time of duration and time of glowing The effect of fire retardant on time of duration and time of glowing is illustrated in Table 2, which shows that untreated board samples made from cottonseed hulls and without binder were almost completely charred when exposed to fire for 5 rain. Even after removing the source of fire, the flaming continued for 104 s for (1) and 99 s for (2) and the carbonised board continued to glow for more than 2 h. With 5% or more of flame retardant the flaming stopped immediately after removal of the source of fire and after-glow was also decreased to 19 s in the case of FR(1) and 7 s for FR(2) with 15% fire retardant. From the results, it is seen that 5% concentration of fire retardant was sufficient.
104 2 1 0 0 0 0
(s)"
Duration time
140 min 52 min 42 min 50s 26'1 min 1-1 min 55 s 19 s
After-glowb
11 8"1 7-0 6-6 4-1 4-0 3-55
(era)
Charred length
FR(1)
Of flaming after removal of source of lire. b Time after removal of source of fire.
Control 0 2 5 8 10 15
Flame retardant (%)
70-5 23-4 21-4 19.8 13.3 10" 1 8"7
(em 2)
Charred area
68"2 15-1 11.7 14-6 6"9 6"5 5-2
(%)
Loss in weight
99 2 0 0 0 0 0
(s)°
Duration time
135 min 52 min 28-8 min 3-9 min 1-8 min 22 s 7s
After-glowb
11 8' 1 6-2 6"0 5.1 4"9 4"3
(cm)
Charred length
68'5 23-4 17.0 16.5 15.7 12"8 8.7
(cm 2)
Charred area
FR( 2)
TABLE 2 Effect of Fire Retardants on Flame Retardant Properties of Particle Boards Prepared from Cottonseed Hulls FR 1--70% borax + 30% boric acid FR2--60% borax + 25% boric acid + 15% ammonium dihydrogen orthophosphate
67-8 15' 1 11.2 10-7 9.3 9.0 6"8
(%)
Loss hi weight
%
'~ .~
.%
Control 0 2 5 8 10 15
Fire retardant (%)
85 172.2 17 I-8 ! 15 108 102 97
(kg c,.-
2)
Bending strength
1"32 I "30 1-29 1"31 1.29 1.26 1"29
Density (gcm - 3)
FR(1)
157 62 65 37 34 41 34
(%)
Water absorption
126 I 12 80 47 45 49 57
(%)
Thickness swelling
81 152 93 103 98 98 66
(kg cm- 2)
Bending strength
I-31 1.31 1'26 1"26 1'26 1-32 1'27
Density (gcm - 3)
(%)
154 64 83 82 57 90 78
Water absorption
FR( 2 )
(%)
124 I 12 92 81 72 92 119
Thickness swelling
TABLE 3 Effect of Fire Retardants on Physical and Mechanical Properties of Particle Boards Prepared from Cottonseed Hulls FR(I)--70% borax + 30% boric acid. FR(2)---60% borax + 25% boric acid + 15% ammonium dihydrogen orthophosphate.
I-,J O
~-
,-, ,~.
,~ "~
e~
202
S. N. Pandey, R. M. Gurjar
Charred length, charred area and loss in weight The effect of fire retardant on charred length, charred area and loss in weight is shown in Table 2. The fire retardants decreased loss in weight from 68.2% to 5.2% in the case of(l) and 67-8% to 6"8% in the case of (2). Similarly, charred length and charred area decreased with increase in concentration of flame retardant. The effects of different concentrations of fire retardant material on physical and mechanical properties of the finished boards are shown in Table 3.
Bending strength It may be seen that increase in concentration of fire retardants decreased the bending strength. Concentrations of fire retardants from 0% to 15% decreased the bending strength of finished board from 172"2kgcm -2 to 97.3cm -2 and 152.2kgcm -2 to 65.6kgcm -2. This may be related to degradation of cellulose fibre by the flame retardants.
Water absorption and per cent thickness swelling It is seen from Table 3 that the water absorption is improved by the addition of flame retardants. The effect of FR(1) was more pronounced than that of FR(2) on water resistance property which may be due to the bulk action of the flame retardant material. From the above discussion it is concluded that both the fire retardant materials increased water resistance of the boards while decreasing bending strength. The ideal concentration of fire retardant materials to attain good flameproofing is found to be 5% which reduced duration of flaming to reach 0s and after-glow to 3.9 min from 135 rain in the case of FR(2). Based on this, cheaper and better quality fire resistant particle boards can be made from cottonseed hulls. These boards can be used in various ways such as in ceiling tiles, partitioning, false ceilings, interior decorative sheets, etc. This will prevent fire hazards in order to protect life and property if used on a large scale. ACKNOWLEDGEMENT The authors express their thanks to the Director, Cotton Technological Research Laboratory, for permission to publish this work.
Flame retarding particle boards
203
REFERENCES Bass, L. W. & Olcott, H. S. (1940). A chronology of cottonseed technology, Ind. Engng. Chem., News Ed., 18, 139-42. Erickson, H. D. (1962). Some aspects of method in determining cellulose in wood. TAPPL 45, 710. Indian Standard Specification IS-2380 IlSI) (1963). Methods of test for wood particle boards from other lignocellulosic materials. Pandey, S. N. (1971). Cotton seed: A valuable agricultural product, Indian Farming (June), 21(3). Pandey, S. N. & Gurjar, R. M. (1985). Production of particle boards from cotton seed hulls, Agricultural Wastes, 13, 287-93. Peters, F. N. (1936). The furans, Ind. Engng. Chem.. 28, 755-9. TA PPI standards and suggested methods (1980). Technical Association of the Pulp and Paper Industry, New York, T-200 to T-265. Wise, L. B., D'Addieio, A. A. & Murphy, M. (1946). Method of determining holocellulose in wood, Paper Trade Journal, 122, 35.
Effects of Flame Retardants on the Properties of Particle Boards Prepared from Cottonseed Hulls S. N. P a n d e y & R. M. G u r j a r Cotton Technological Research Laboratory (ICAR), Adenwala Road, Matunga, Bombay-400019,India (Received 22 February 1986; accepted 29 May 1986)
A BS T R A C T The effects of fire retardants on the properties of particle boards made from cottonseed hulls were studied. The boards were treated with (1) 70% borax + 3 0 % boric acid (FR(1)); (2) 60% borax+25% boric acid+15% ammonium dihydrogen orthophosphate ( F R ( 2 ) ) and were evaluated for duration of flaming, after-glow, charred area, charred length and per cent loss in weight, along with physico-mechanical properties. Fire retardant properties, water resistance and per cent thickness swelling improved, and bending strength decreased, with increase in concentration of fire retardants. Treatment (2) wasfound to be the better fire retardant since it served the dual purposes of flame and glow retardation.
INTRODUCTION The annual production of cottonseed in India is about 3 million tonnes from which about 1"2 million tonnes of cottonseed hull, an outer covering of the seed, is available. Besides the use of cottonseed as a source of oil, cake and linters, the cottonseed hulls can also be used for various other purposes (Pandey, 1971). In addition to using hulls to produce xylose (Bass 8,s Olcott, 1940) and a highly effective activated carbon from hull bran, furfural (Peters, 1936) a very important chemical can be isolated, and the hull can also be used for the production of various types of good strength particle boards (Pandey & Gurjar, 1985). Cottonseed is a horny material which protects the seed kernel by an 197 Biological Wastes 0269-7483/87/$03.50 O ElsevierApplied SciencePublishers Ltd, England, 1987. Printed in Great Britain
198
s. N. Pandey, R. M. Gurjar
external hard brownish covering, chemically consisting of three major components--pentosans, cellulose and lignin (:~-cellulose, 45%-47%; pentosan, 25%-27% and lignin, 18%-20%). Considering fire as a hazard it is essential to protect buildings, furniture, etc., from fire. Fire-resistant materials such as polyammonium phosphate and aluminium sulphite, boric acid, borax and sodium silicate can be used to improve fire- and water-resistance properties of particle boards. The present work studied the effects of borax, boric acid and a m m o n i u m dihydrogen orthophosphate, mixed in different proportions and concentrations while preparing the particle board from cottonseed hull, on physical, mechanical and fire retardant properties.
METHODS
Hulls and analysis Mixed cottonseed hulls of different varieties were obtained from local expellers. Urea formaldehyde resin and a m m o n i u m chloride were used as binder and catalyst, respectively. Borax, boric acid and a m m o n i u m dihydrogen orthophosphate were used as fire retardant materials. Chemical analysis of the mixed hulls was carried out for holocellulose (Wise et al., 1946; Erickson, 1962), lignin, pentosans and ash according to T A P P I standards and suggested methods and the results are given in Table 1. Separate samples were used for each analysis. TABLE 1 Chemical Analysis of Cottonseed Hull (% dry weight) Ash Lignin Pentosan Holocellulose
2-74 31"5 18.5 64-7
Preparation of particle boards Cottonseed hull was ground to suitable size in a laboratory beater type mill. Urea formaldehyde resin solution (15%) as a binder and 3% (on resin) a m m o n i u m chloride as catalyst were sprayed on the ground material, which was treated with different solutions of known concentration of fire retarding materials. These were 70% borax + 30% boric acid; 60% borax
Flame retarding particle boards
199
+ 25% boric acid + 15% a m m o n i u m dihydrogen orthophosphate. The moisture content of the material was adjusted by drying before pressing. The material was framed into a false impression by cold pressing and then pressed between heated platens in a hydraulic press. In order to obtain the desired thickness, pressure, temperature and time were adjusted while pressing. The boards were prepared under pressure, 16 kg c m - 2 for 4 rain at a platen temperature of 150°C. The moisture in the material acted as plasticizer and the lignin as a binder which becomes soft at higher temperatures. The boards were then trimmed and kept for conditioning for dimensional stability before use. A control board was prepared as above from cotton hulls without binder and fire retardants. The prepared boards were tested for bending strength, density, water absorption after 2h and per cent thickness swelling as per ISI methods (Indian Standard Specification IS-2380, 1963). These boards were also tested for the fire retardant properties, duration of flaming, after-glow, charred length, charred area and per cent loss in weight by standard methods. The time of exposure of the specimen to fire was set to 5 min. The test methods are defined as follows. Duration offlaming--The period which elapses between the removal of the igniting flame and the time that the specimen ceases to flame, expressed in seconds. Time of glowing--The spread of after-glow, observed until it has ceased, expressed in seconds. RESULTS AND D I S C U S S I O N The control sample shown in Tables 2 and 3 is without binder and fire retardant, to avoid the interference in properties, while other samples contain 15% of binder and concentrations of fire retardant from 0% to 15%.
Time of duration and time of glowing The effect of fire retardant on time of duration and time of glowing is illustrated in Table 2, which shows that untreated board samples made from cottonseed hulls and without binder were almost completely charred when exposed to fire for 5 rain. Even after removing the source of fire, the flaming continued for 104 s for (1) and 99 s for (2) and the carbonised board continued to glow for more than 2 h. With 5% or more of flame retardant the flaming stopped immediately after removal of the source of fire and after-glow was also decreased to 19 s in the case of FR(1) and 7 s for FR(2) with 15% fire retardant. From the results, it is seen that 5% concentration of fire retardant was sufficient.
104 2 1 0 0 0 0
(s)"
Duration time
140 min 52 min 42 min 50s 26'1 min 1-1 min 55 s 19 s
After-glowb
11 8"1 7-0 6-6 4-1 4-0 3-55
(era)
Charred length
FR(1)
Of flaming after removal of source of lire. b Time after removal of source of fire.
Control 0 2 5 8 10 15
Flame retardant (%)
70-5 23-4 21-4 19.8 13.3 10" 1 8"7
(em 2)
Charred area
68"2 15-1 11.7 14-6 6"9 6"5 5-2
(%)
Loss in weight
99 2 0 0 0 0 0
(s)°
Duration time
135 min 52 min 28-8 min 3-9 min 1-8 min 22 s 7s
After-glowb
11 8' 1 6-2 6"0 5.1 4"9 4"3
(cm)
Charred length
68'5 23-4 17.0 16.5 15.7 12"8 8.7
(cm 2)
Charred area
FR( 2)
TABLE 2 Effect of Fire Retardants on Flame Retardant Properties of Particle Boards Prepared from Cottonseed Hulls FR 1--70% borax + 30% boric acid FR2--60% borax + 25% boric acid + 15% ammonium dihydrogen orthophosphate
67-8 15' 1 11.2 10-7 9.3 9.0 6"8
(%)
Loss hi weight
%
'~ .~
.%
Control 0 2 5 8 10 15
Fire retardant (%)
85 172.2 17 I-8 ! 15 108 102 97
(kg c,.-
2)
Bending strength
1"32 I "30 1-29 1"31 1.29 1.26 1"29
Density (gcm - 3)
FR(1)
157 62 65 37 34 41 34
(%)
Water absorption
126 I 12 80 47 45 49 57
(%)
Thickness swelling
81 152 93 103 98 98 66
(kg cm- 2)
Bending strength
I-31 1.31 1'26 1"26 1'26 1-32 1'27
Density (gcm - 3)
(%)
154 64 83 82 57 90 78
Water absorption
FR( 2 )
(%)
124 I 12 92 81 72 92 119
Thickness swelling
TABLE 3 Effect of Fire Retardants on Physical and Mechanical Properties of Particle Boards Prepared from Cottonseed Hulls FR(I)--70% borax + 30% boric acid. FR(2)---60% borax + 25% boric acid + 15% ammonium dihydrogen orthophosphate.
I-,J O
~-
,-, ,~.
,~ "~
e~
202
S. N. Pandey, R. M. Gurjar
Charred length, charred area and loss in weight The effect of fire retardant on charred length, charred area and loss in weight is shown in Table 2. The fire retardants decreased loss in weight from 68.2% to 5.2% in the case of(l) and 67-8% to 6"8% in the case of (2). Similarly, charred length and charred area decreased with increase in concentration of flame retardant. The effects of different concentrations of fire retardant material on physical and mechanical properties of the finished boards are shown in Table 3.
Bending strength It may be seen that increase in concentration of fire retardants decreased the bending strength. Concentrations of fire retardants from 0% to 15% decreased the bending strength of finished board from 172"2kgcm -2 to 97.3cm -2 and 152.2kgcm -2 to 65.6kgcm -2. This may be related to degradation of cellulose fibre by the flame retardants.
Water absorption and per cent thickness swelling It is seen from Table 3 that the water absorption is improved by the addition of flame retardants. The effect of FR(1) was more pronounced than that of FR(2) on water resistance property which may be due to the bulk action of the flame retardant material. From the above discussion it is concluded that both the fire retardant materials increased water resistance of the boards while decreasing bending strength. The ideal concentration of fire retardant materials to attain good flameproofing is found to be 5% which reduced duration of flaming to reach 0s and after-glow to 3.9 min from 135 rain in the case of FR(2). Based on this, cheaper and better quality fire resistant particle boards can be made from cottonseed hulls. These boards can be used in various ways such as in ceiling tiles, partitioning, false ceilings, interior decorative sheets, etc. This will prevent fire hazards in order to protect life and property if used on a large scale. ACKNOWLEDGEMENT The authors express their thanks to the Director, Cotton Technological Research Laboratory, for permission to publish this work.
Flame retarding particle boards
203
REFERENCES Bass, L. W. & Olcott, H. S. (1940). A chronology of cottonseed technology, Ind. Engng. Chem., News Ed., 18, 139-42. Erickson, H. D. (1962). Some aspects of method in determining cellulose in wood. TAPPL 45, 710. Indian Standard Specification IS-2380 IlSI) (1963). Methods of test for wood particle boards from other lignocellulosic materials. Pandey, S. N. (1971). Cotton seed: A valuable agricultural product, Indian Farming (June), 21(3). Pandey, S. N. & Gurjar, R. M. (1985). Production of particle boards from cotton seed hulls, Agricultural Wastes, 13, 287-93. Peters, F. N. (1936). The furans, Ind. Engng. Chem.. 28, 755-9. TA PPI standards and suggested methods (1980). Technical Association of the Pulp and Paper Industry, New York, T-200 to T-265. Wise, L. B., D'Addieio, A. A. & Murphy, M. (1946). Method of determining holocellulose in wood, Paper Trade Journal, 122, 35.