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Water absorption and swelling characteristics of coir pith particle board
Bioresource Technology 71 (2000) 93±94
Short communication
Water absorption and swelling characteristics of coir pith particle board R. Viswanathan*, L. Gothandapani, R. Kailappan Department of Agricultural Processing, College of Agricultural Engineering, Tamil Nadu Agricultural University, Coimbatore 641 003, India Received 10 February 1999; received in revised form 21 March 1999; accepted 30 March 1999
Abstract The water absorption and swelling characteristics along the surface and thickness were determined for particle boards made from coir pith of 0.4, 0.8, 1.2 and 2.1 mm average particle sizes using phenol±formaldehyde and urea±formaldehyde resins. The water absorption, swelling along surface and thickness ranged from 30% to 133%, 0.7% to 3.7% and 24% to 112.6%, respectively. The water absorption and swelling were least for the board made from largest-size particles and phenol±formaldehyde resin. Ó 1999 Elsevier Science Ltd. All rights reserved. Keywords: Coir pith; Particle board; Water absorption; Swelling in water
1. Introduction Fibre from coconut husk is extracted on a commercial scale by natural retting (golden yellow ®bre) or mechanical (non-retting) process (brown ®bre). In the ®bre extraction process, coir pith is obtained as a waste material, and for want of proper utilisation, this coir pith is dumped outside the coir factory. Medium density particle board using coir pith has been produced and the strength characteristics determined (Viswanathan and Gothandapani, 1998). This board, made of phenol± formaldehyde resin, meets the strength requirements of the Bureau of Indian Standards. The suitability of the particle board for the interior and exterior use is based on the water absorption and swelling in water. In this report, water absorption and swelling characteristics of the coir pith particle boards were evaluated. 2. Methods 2.1. Production of test boards Particle boards of size 250 mm ´ 250 mm by 12 mm thickness with density 0.9 g/cc were produced from the coir pith of particle sizes 2.1, 1.2, 0.80 and 0.40 mm, mixed sizes of particles with ®bre (MF) and mixed size *
Corresponding author.
of particles without ®bre (M). The unit operations included drying of coir pith, mixing of resin, mat-forming, pressing and curing. Phenol±formaldehyde and urea± formaldehyde resins of liquid type with hardeners were used for the production of the particle boards at the following levels of process parameters which had been found to be optimum. Parameter
Proportion of resin (%) Curing duration (min) Curing temperature (°C)
Resin Phenol± formaldehyde
Urea± formaldehyde
16.7 26 138
20.4 17 139
The experimental arrangement used for the production of particle board from coir pith consisted of a power-cum-hand operated hydraulic press, temperaturecontrolled heating arrangement, moulding box and loading and unloading provisions. The hydraulic press used was of 60 ton capacity and powered by a 2 hp motor. A moulding box to produce the particle board of size 250 mm ´ 250 mm was made and used. The plunger to compress the resinated coir pith was mounted to the ram of the hydraulic press and moved along the ram. For heating of resinated coir pith during pressing, strip heaters were provided in the plate and the plunger. The temperatures of the surfaces were controlled using a temperature indicator cum controller.
0960-8524/00/$ ± see front matter Ó 1999 Elsevier Science Ltd. All rights reserved. PII: S 0 9 6 0 - 8 5 2 4 ( 9 9 ) 0 0 0 5 7 - 7
94
R. Viswanathan et al. / Bioresource Technology 71 (2000) 93±94
Table 1 Water absorption and swelling characteristic of coir pith particle board Particle size, mm
a
After 2 h
After 24 h
Phenol±formaldehyde
Urea±formaldehyde
Phenol±formaldehyde
Urea±formaldehyde
62.9 56.9 41.7 29.8 34.4 48.1
76.6 66.5 52.6 45.4 50.1 56.2
107.1 94.9 86.2 74.4 76.7 92.2
132.7 123 104.8 87.5 93.9 116.6
(b) Swelling along surface (%) 0.45 2.4 0.80 1.4 1.20 1.1 2.10 0.6 M 1.1 MF 1.5
2.9 2.2 1.5 1.1 1.7 2.3
5.2 4.1 3.5 2.7 2.9 3.7
3.8 2.8 2.3 1.7 2 2.6
(c) Swelling along thickness (%) 0.45 59.7 0.80 51.1 1.20 46.9 2.10 24 M 29.4 MF 47.4
74.3 60.5 57 44.6 53.9 61.7
60.7 56.1 48.5 38.2 39.5 48.7
126.1 113.9 97.3 83 98.2 107.8
(a) Water absorption (%) 0.45 0.80 1.20 2.10 M MF
a
See Methods.
2.2. Testing of the particle board The particle boards produced were evaluated for water absorption and swelling in water as in Ref. IS: 2380, 1977. Board samples made of various particle sizes and resins were fully soaked in water at room temperature for 2 and 24 h. At the end of these periods, the samples were weighed and dimensions measured. From the increase in mass and dimensions, the per cent water absorption and per cent swelling along surface and thickness were calculated. Three pieces of each sample were used for replicating the determination. 3. Results and discussion The per cent water absorption and swelling along the surface and thickness by the coir pith particle board is given in Table 1. All these properties are higher for 24 h of soaking than soaking for 2 h. At all the treatment combinations of particle size and resin, these properties decreased with increase in particle size. The higher water absorption by the boards made from smaller size particles would be due to the larger surface area which absorbs more water. The minimum water absorptions after 2 and 24 h are 29.8% and 74.4% for the phenol±formaldehyde-bonded coir pith particle
board made using the particle size 2.1 mm, as against the requirements of 25% and 50%, respectively, for IS:3087, 1985. The coir pith particle board does not meet the requirements of the Bureau of Indian Standards for water absorption. The per cent swelling was greater in urea±formaldehyde resin bonded particle board at all particle sizes than the phenol±formaldehyde resin bonded particle board. The minimum swelling of 24% along the thickness was noted for the particle size 2.1 mm for 2 h soaking and the maximum of 126.1% for the particle size of 0.45 mm for 24 h of soaking. The minimum swelling along thickness required by IS:3087, 1985 is 10%, which was not been achieved by the coir pith particle board. Hence these boards are suitable for interior use only. References IS: 2380 (Part I ± XXI), 1977. Methods of test for wood particle boards and boards from other lignocellulosic materials. Bureau of Indian Standards, New Delhi, pp. 1±66. IS: 3087, 1985. Speci®cation for wood particle board (medium density) for general purposes. Bureau of Indian Standards, New Delhi, pp. 1±20. Viswanathan, R., Gothandapani, L., 1998. Mechanical Properties of Coir Pith Particle Boards. Bioresources Technology 67 (1), 93±94.
Short communication
Water absorption and swelling characteristics of coir pith particle board R. Viswanathan*, L. Gothandapani, R. Kailappan Department of Agricultural Processing, College of Agricultural Engineering, Tamil Nadu Agricultural University, Coimbatore 641 003, India Received 10 February 1999; received in revised form 21 March 1999; accepted 30 March 1999
Abstract The water absorption and swelling characteristics along the surface and thickness were determined for particle boards made from coir pith of 0.4, 0.8, 1.2 and 2.1 mm average particle sizes using phenol±formaldehyde and urea±formaldehyde resins. The water absorption, swelling along surface and thickness ranged from 30% to 133%, 0.7% to 3.7% and 24% to 112.6%, respectively. The water absorption and swelling were least for the board made from largest-size particles and phenol±formaldehyde resin. Ó 1999 Elsevier Science Ltd. All rights reserved. Keywords: Coir pith; Particle board; Water absorption; Swelling in water
1. Introduction Fibre from coconut husk is extracted on a commercial scale by natural retting (golden yellow ®bre) or mechanical (non-retting) process (brown ®bre). In the ®bre extraction process, coir pith is obtained as a waste material, and for want of proper utilisation, this coir pith is dumped outside the coir factory. Medium density particle board using coir pith has been produced and the strength characteristics determined (Viswanathan and Gothandapani, 1998). This board, made of phenol± formaldehyde resin, meets the strength requirements of the Bureau of Indian Standards. The suitability of the particle board for the interior and exterior use is based on the water absorption and swelling in water. In this report, water absorption and swelling characteristics of the coir pith particle boards were evaluated. 2. Methods 2.1. Production of test boards Particle boards of size 250 mm ´ 250 mm by 12 mm thickness with density 0.9 g/cc were produced from the coir pith of particle sizes 2.1, 1.2, 0.80 and 0.40 mm, mixed sizes of particles with ®bre (MF) and mixed size *
Corresponding author.
of particles without ®bre (M). The unit operations included drying of coir pith, mixing of resin, mat-forming, pressing and curing. Phenol±formaldehyde and urea± formaldehyde resins of liquid type with hardeners were used for the production of the particle boards at the following levels of process parameters which had been found to be optimum. Parameter
Proportion of resin (%) Curing duration (min) Curing temperature (°C)
Resin Phenol± formaldehyde
Urea± formaldehyde
16.7 26 138
20.4 17 139
The experimental arrangement used for the production of particle board from coir pith consisted of a power-cum-hand operated hydraulic press, temperaturecontrolled heating arrangement, moulding box and loading and unloading provisions. The hydraulic press used was of 60 ton capacity and powered by a 2 hp motor. A moulding box to produce the particle board of size 250 mm ´ 250 mm was made and used. The plunger to compress the resinated coir pith was mounted to the ram of the hydraulic press and moved along the ram. For heating of resinated coir pith during pressing, strip heaters were provided in the plate and the plunger. The temperatures of the surfaces were controlled using a temperature indicator cum controller.
0960-8524/00/$ ± see front matter Ó 1999 Elsevier Science Ltd. All rights reserved. PII: S 0 9 6 0 - 8 5 2 4 ( 9 9 ) 0 0 0 5 7 - 7
94
R. Viswanathan et al. / Bioresource Technology 71 (2000) 93±94
Table 1 Water absorption and swelling characteristic of coir pith particle board Particle size, mm
a
After 2 h
After 24 h
Phenol±formaldehyde
Urea±formaldehyde
Phenol±formaldehyde
Urea±formaldehyde
62.9 56.9 41.7 29.8 34.4 48.1
76.6 66.5 52.6 45.4 50.1 56.2
107.1 94.9 86.2 74.4 76.7 92.2
132.7 123 104.8 87.5 93.9 116.6
(b) Swelling along surface (%) 0.45 2.4 0.80 1.4 1.20 1.1 2.10 0.6 M 1.1 MF 1.5
2.9 2.2 1.5 1.1 1.7 2.3
5.2 4.1 3.5 2.7 2.9 3.7
3.8 2.8 2.3 1.7 2 2.6
(c) Swelling along thickness (%) 0.45 59.7 0.80 51.1 1.20 46.9 2.10 24 M 29.4 MF 47.4
74.3 60.5 57 44.6 53.9 61.7
60.7 56.1 48.5 38.2 39.5 48.7
126.1 113.9 97.3 83 98.2 107.8
(a) Water absorption (%) 0.45 0.80 1.20 2.10 M MF
a
See Methods.
2.2. Testing of the particle board The particle boards produced were evaluated for water absorption and swelling in water as in Ref. IS: 2380, 1977. Board samples made of various particle sizes and resins were fully soaked in water at room temperature for 2 and 24 h. At the end of these periods, the samples were weighed and dimensions measured. From the increase in mass and dimensions, the per cent water absorption and per cent swelling along surface and thickness were calculated. Three pieces of each sample were used for replicating the determination. 3. Results and discussion The per cent water absorption and swelling along the surface and thickness by the coir pith particle board is given in Table 1. All these properties are higher for 24 h of soaking than soaking for 2 h. At all the treatment combinations of particle size and resin, these properties decreased with increase in particle size. The higher water absorption by the boards made from smaller size particles would be due to the larger surface area which absorbs more water. The minimum water absorptions after 2 and 24 h are 29.8% and 74.4% for the phenol±formaldehyde-bonded coir pith particle
board made using the particle size 2.1 mm, as against the requirements of 25% and 50%, respectively, for IS:3087, 1985. The coir pith particle board does not meet the requirements of the Bureau of Indian Standards for water absorption. The per cent swelling was greater in urea±formaldehyde resin bonded particle board at all particle sizes than the phenol±formaldehyde resin bonded particle board. The minimum swelling of 24% along the thickness was noted for the particle size 2.1 mm for 2 h soaking and the maximum of 126.1% for the particle size of 0.45 mm for 24 h of soaking. The minimum swelling along thickness required by IS:3087, 1985 is 10%, which was not been achieved by the coir pith particle board. Hence these boards are suitable for interior use only. References IS: 2380 (Part I ± XXI), 1977. Methods of test for wood particle boards and boards from other lignocellulosic materials. Bureau of Indian Standards, New Delhi, pp. 1±66. IS: 3087, 1985. Speci®cation for wood particle board (medium density) for general purposes. Bureau of Indian Standards, New Delhi, pp. 1±20. Viswanathan, R., Gothandapani, L., 1998. Mechanical Properties of Coir Pith Particle Boards. Bioresources Technology 67 (1), 93±94.