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Physico-Mechanical Properties of Wood and Non-Wood Plaster of Paris Bonded Composite Ceiling Boards
Temidayo Emmanuel Omoniyi Kenny Ajobiewe 1
1 University of Ibadan
Ibadan, Oyo State, 900001, Nigeria
DOI: 10.22178/pos.58-9
LCC Subject Category: TH6014-6081
Received 23.04.2020 Accepted 28.05.2020 Published online 31.05.2020
Corresponding Author: Temidayo Emmanuel Omoniyi [email protected]
© 2020 The Authors. This article is licensed under a Creative Commons Attribution 4.0 License l^O—
Abstract. Woody (Alzibia zygia) and Non-woody (rattan and yarn strands) fibres were used comparatively to improve the physicomechanical properties of Plaster of Paris bonded composite which is used as ceiling boards. The addition of fibre reinforcement in a discrete form improves the engineering properties of the Plaster of Paris. The woody and nonwoody residues were varied in 10, 20, 30, 40, and 50% of the whole mix while the Plaster of Paris used were in the ratio 100 (control), 90, 80, 70, 60, and 50 %. The mean density of the composite produced is 3250 kg/m3. The mean thickness swelling after 2 and 24 hours is 0.84 % and 0.88 % respectively with the mean water absorption at 13.8% after 2 hours and 16.2 % after 24 hours. The MOR and MOE of the composites produced ranged from 1.21-1.22 N/mm2, 2431-51488N/mm2 for sawdust, 1.17-1.22 N/mm2, 10027-49940 N/mm2 for yarn strands and 1.201.22 N/mm2, 23566-86210 N/mm2 for the rattan strands. The results showed physicomechanical properties of POP-bonded fibre reinforced composites were increased for both wood and non-wood fibres and rattan strands compared best.
Keywords: Wood composites; Physico-mechanical; Fibre reinforcement; Plaster of Paris; Ceiling board.
INTRODUCTION
Reinforced Plaster of Paris Composite ceiling boards is a new decorative and finishing material that is gaining increasing importance and usage. Plaster of Paris or gypsum is a very soft sulfate mineral of chemical formulae CaSO42H2O which presents itself often as monoclinic, massive, flat, or elongated and generally prismatic crystals with its colour ranging from colorless to white [1]. In recent years, asbestos materials for making ceiling boards have been banned in many advanced countries due to its carcinogenic nature, with agencies in construction industries having identified its real and potentially adverse effect on humans [2]. Locally sourced building materials that would facilitate sustainable development remain underdeveloped to a socially and economically acceptable level, owing to the low level of development of the economy [3].
Authors [4] reported that composite is designed to take advantage of the desirable characteristics of constituent materials by choosing an appropriate combination of matrix and reinforcement
material, thus producing a new material that meets the exact requirements of a particular application. Yarn is a long continuous length of interlocked fibres suitable for use in the production of textiles, sewing, crocheting, knitting weaving, embroidery, and rope making, while rattan is a stick made from the stem of the rattan palms. Rattan canes are numbered among the important commercial non-timber forest products employed in the furniture industry in the tropics, however, over 30% of rattan harvested at any time particular for furniture manufacture are wastes [5]. Alzibia zygia is a deciduous tree nine to thirty meters tall with a spreading crown and a graceful architectural form and its bole tall and clear, around 240 cm in diameter. It has a dark grey and smooth surface [6]. These materials experimented as reinforcement to improve the properties of Plaster of Paris to produce durable, affordable, and environmentally friendly (non-carcinogenic substances) material suitable structurally as ceiling boards.
METHODOLOGY
Materials Collection. Sawdust of Alzibia zygia collected from the Bodija plank market in Ibadan was graded and sieved to remove -impurities, then oven-dried to around 101 °C to reduce the moisture content of the fibre. Rattan, yarn fibres and Plaster of Paris were purchased from a retail outlet also in Ibadan.
Procedure. The materials were then weighed and batched in accordance to the research methods (Tables 1, 2, and 3). The mixing was done manually with potable water and added into a prepared wooden mold. The mixture was allowed to sit for some minutes before curing take place. The produced composite materials were then subjected to the test to investigate their physical and mechanical properties (Table 1-3).
The following tests were carried out on the specimens.
Density. After curing, the samples were weighed on a digital weighing scale and their corresponding weight in kilograms was recorded. The density of the materials was calculated with the following equation (1):
w
d = -, (1) v
where d is the density in (kg/m3); w is the weight of the composite produced; v is the volume of the produced composite.
Specific gravity. The specific gravity was calculated using this equation (2):
Table 1 - Plaster of Paris and Alzibia zygia (Ayunre)
Samples POP (%) Wood fibre (%) Samples produced
PWF1 100 0 3
PWF2 90 10 3
PWF3 80 20 3
PWF4 70 30 3
PWF5 60 40 3
PWF6 50 50 3
SG = —, (2)
dw
where SG is the specific gravity of samples; dc is the density of composites produced (kg/m3);
dw is the density of water in (1000 kg/m3).
PWF = POP + woof fibre
Table 2 - Plaster of Paris and Rattan fibre
Samples POP (%) Rattan fibre (%) Samples produced
PRF1 100 0 3
PRF2 90 10 3
PRF3 80 20 3
PRF4 70 30 3
PRF5 60 40 3
PRF6 50 50 3
PRF = POP + ratta n fibre
Table 3 - Plaster of Paris and yarn ibre
Samples POP (%) Rattan fibre (%) Samples produced
PYF1 100 0 3
PYF2 90 10 3
PYF3 80 20 3
PYF4 70 30 3
PYF5 60 40 3
PYF6 50 50 3
Water Absorption and Thickness swelling. The specimen from each specimen was submerged horizontally under 50 mm of distilled water maintained at a room temperature of about 27 °C. The amount of water absorbed after 2 hours and 24 hours were recorded.
w — w,
% water = -1X100,
w,
(3)
PYF = POP + yarn fibre
w1 and w2 is the initial and final weight before and after soaking respectively.
% thickness swelling = ——— x 100, (4)
ti
t1 and t2 is the initial and final thickness before and after soaking.
Modulus of Rupture (MOR). This was conducted to approximate the bending strength of the produced composite materials. The samples were tested using the universal test machine (UTM) of the Department of Agricultural and Environmental Engineering, University of Ibadan.
MOR =
3PL 2BH2
where P is the maximum force/ load in (N); L - span of the board (mm); B - width of the test specimen (mm); H - thickness of the test specimen (mm).
Modulus of Elasticity (MOE):
(5)
MOE = ■
PLl
(6)
4DBH3 '
where P is the maximum force / load in (N); L - span of the board (mm); B - width of the test specimen (mm); H - thickness of the test specimen (mm); D - deflection at mid-point.
RESULTS AND DISCUSSION
Density and specific gravity. Figure 1-2 shows the produced composite materials.
Figure 2 - Samples of the fibre composites
Table 4 shows the densities and specific gravity of the material produced. The densities varies from 3200 kg/m3 to 3900 kg/m3 (wood fibre), 2700 kg/m3 to 4500 kg/m3 (rattan fibre), 2000 kg/m3 to 4500 kg/m3 (yarn fibre) and 4700 kg/m3 (POP only). Samples produced with POP alone have higher densities due to the presence of reinforced fibres (which tends to be lighter) in other samples. Increase in the fibre content of the composite produced decreases the density and specific gravity of the material which is in accordance to the report on wood composite by [5].
Thickness Swelling and Water Absorption. Table 5 and 6 shows the water absorption and thickness swelling percentage of the composite materials respectively. Cumulatively, the higher the fibre content in the composite, the higher the water absorption, which may be due to the hydrophilic nature of the wood and the other fibres.
Figure 1 - Producing samples with Vibrating table
Table 4 - Density and specific gravity of composites
Sample, Pop/fibre Ôpwf (kg/m3) dprf (kg/m3) dpyf (kg/m3) SGpwf SGprf SGpyf
100/0 4700 4700 4700 4.7 4.7 4.7
90/10 3900 4500 4500 3.9 4.5 4.5
80/20 3500 4000 3500 3.5 4 3.5
70/30 3480 3000 3200 3.48 3 3.2
60/40 3320 3100 2700 3.32 3.1 2.7
50/50 3200 2700 2000 3.2 2.7 2
The behaviour of the produced composites was similarly reported by [8], that the presence of hydroxyl groups inside the cellulose and hemicel-luloses attract the water molecules and form hydrogen bonding. Moreover, due to the porous
structure of wood fibres, the composites with higher wood content absorb more water which penetrates into the pores according to the principle of capillary flow. The yarn fibre absorbed the lowest amount of water content.
Table 5 - Wal er absorption (%) of composites produced
Sample %WApwf %WApwf %WAprf %WAprf %WApyf %WApyf
(2 hrs) (24 hrs) (2 hrs) (24 hrs) (2 hrs) (24 hrs)
100/0 11.53 15.2 11.55 15.23 11.63 11.24
90/10 14.87 15.75 13.98 14.24 12.32 12.94
80/20 15.06 16.98 14.28 14.93 12.72 13.19
70/30 15.47 18.78 14.72 15.34 13.01 13.89
60/40 15.90 19.22 14.84 15.45 13.59 14.14
50/50 15.98 20.02 15.77 16.32 14.34 15.21
Table 6 - Thickness swelling (%) of composites
Sample %TSPWF %TSPWF %TSPRF %TSPRF %TSPYF %TSPYF
(2 hrs) (24 hrs) (2 hrs) (24 hrs) (2 hrs) (24 hrs)
100/0 0.39 0.59 0.39 0.59 0.39 0.59
90/10 0.58 0.78 0.48 0.69 0.40 0.58
80/20 0.77 0.88 0.51 0.78 0.58 0.59
70/30 0.96 1.18 0.76 0.98 0.58 0.67
60/40 1.28 1.57 0.98 1.13 0.77 0.98
50/50 1.35 1.96 1.17 1.23 0.79 0.99
Table 6 shows the results of the thickness swelling test. Generally, the change in thickness of the produced composites is very minimal after 2 and 24 hours. The yarn fibre has the best performance under the thickness swelling test. As reported by [2] increase in the fibre ratio of the composites increases the thickness swelling after water immersion.
Modulus of Elasticity (MOE) and Modulus of Rupture (MOR). The strength properties of the composites were shown in table 7. The introduction of fibre tends to increase the Modulus of Elasticity of the composites as the primary objective of fibres as filler is to increase the stiffness of WPC. The results tally with [9] report, in which the ten-
sile and flexural strength slightly increased with an increasing wood fibre content of a WPC. The rattan fibre reinforced composites has the highest range of MOE values of 40167 KN/mm2 to 50982 KN/mm2, wood filler composites has a range of 39310 KN/mm2 to 43477 KN/mm2, and the yarn filler composites range from 39567 KN/mm2 to 43270 KN/mm2. The composites exhibit the same behaviour for the MOE and MOR test. The rattan performs best with MOR values of 1.221 KN/mm2 to 1.229 KN/mm2, wood fibre ranges from 1.221 KN/mm2 to 1.229 KN/mm2, and yarn fibre ranges from 1.219 KN/mm2 to 1.211 KN/mm2.
Table 7 - Results of MOE and MOR
Sample MOEpwf MOEprf MOEpyf MORpwf MORprf MORpyf
(KN/mm2) (KN/mm2) (KN/mm2) (KN/mm2) (KN/mm2) (KN/mm2)
100/0 32142.9 32142.9 32142.9 1.210 1.210 1.210
90/10 39310.1 40167.38 39567.39 1.221 1.284 1.219
80/20 41488.0 45235.11 41678.78 1.224 1.297 1.219
70/30 42757.9 56567.76 41997.98 1.237 1.307 1.227
60/40 43038.9 51709.78 43018.78 1.228 1.375 1.211
50/50 43477.7 50982.77 43270.77 1.229 1.376 1.228
CONCLUSION
Fibre-POP composites was produced from wood (Alzibia zygia), rattan (Laccosperma secundiflo-rum), and yarn. The composites were tested for strength and physical properties. The results derived implied that:
1. The mechanical properties of Rattan reinforced composite in terms of Modulus of Rupture and Modulus of Elasticity has the highest value meaning that bending strength of rattan reinforced composite is high.
2. The use of fibre to reinforce Plaster of Paris considerably increased the strength properties of the material.
3. There is reduction in environmental pollution through the use of waste fibres to yield a material suitable in ceiling board production.
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