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EVALUATION OF STRENGTH AND SORPTION PROPERTIES OF POLYSTYRENE BONDED COMPOSITES OF MAHOGANY (KHAYA IVORENSIS) AND TEAK (TECTONA GRANDIS) WOODS

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EVALUATION OF STRENGTH AND SORPTION PROPERTIES OF POLYSTYRENE BONDED COMPOSITES OF MAHOGANY (KHAYA IVORENSIS) AND TEAK (TECTONA GRANDIS) WOODS
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   Arid Zone Journal of Engineering, Technology and Environment, June, 2018; Vol. 14(2):201-207 Copyright © Faculty of Engineering, University of Maiduguri, Maiduguri, Nigeria. Print ISSN: 1596-2490, Electronic ISSN: 2545-5818, www.azojete.com.ng   EVALUATION OF STRENGTH AND SORPTION PROPERTIES OF POLYSTYRENE BONDED COMPOSITES OF MAHOGANY ( KHAYA IVORENSIS ) AND TEAK ( TECTONA GRANDIS ) WOODS Adefisan, O.O. (Department of Wood Products Engineering, University of Ibadan, Nigeria.) Email Address:   femiadefisan@hotmail.com, oo.adefisan@mail.ui.edu.ng  Abstract The cost of synthetic resin used for composites production is increasing. Low cost durable glue may be derived from disused polystyrene foams and used in wood composites production. This work therefore examined the strength and sorption properties of polystyrene bonded composites made from particles of Mahogany (  Khaya ivorensis ) and Teak ( Tectona grandis ). Particles of  K. ivorensis  and T. grandis  were mixed with polystyrene (PS) glue in ratios 1:1, 2:1, 1:2 and 3:1, and formed into boards. Functional properties of the PS glue were examined using Fourier Transformed Infrared Radioscopy. Strength and sorption tests were conducted on specimens in accordance with ASTM standards. The results obtained revealed that the glue  possessed hydroxyl, phenyl and aromatic functional groups that enhanced the strength and stability. The fabricated boards possessed moderate strength and dimensional stability indicating their use as indoor insulating components. Increase in the glue content significantly improved the strength and sorption properties of the composites. Optimum flexural properties were obtained at glue mixing ratio of 2:1. Keywords:  Polystyrene foams, wood composites, Mahogany, Teak    1.0 Introduction  A lot of waste is generated worldwide due to daily human activities. Prominent amongst these are wood wastes which occur due to poor sawing patterns, lack of expertise of the machine operators, use of obsolete facilities, etc. and polystyrene foam, a petroleum based polymer of styrene used for insulation and packaging. While wood wastes are hazardous to the mill, the mill workers, the wood and the wood products, polystyrene which has a low scrap value is not biodegradable. Therefore, these items are mostly disposed of in landfills resulting in environmental pollution (Kwon et al  ., 2009; Kan and Demirboga, 2009; Ricky et al  ., 2010). A means of curtailing these deleterious effects could be in the production of wood polymer composites. Wood Polymer Composites (WPCs) incorporate wood particles as fillers and reinforcing agents while the polymer acts as matrix. They are lightweight, environmentally friendly products with increased hardness, improved dimensional stability, and possess abrasion and decay resistance. They can be integrated in furniture items such as table tops, cabinet manufacture and in low cost building components such as floor and wall tiles, ceiling boards etc. (Poletto, 2016). While wood (fibres or particles) is hydrophilic in nature which may negatively affect the mechanical  properties of the derived composite products, most synthetic resins which are used for bonding wood composites on the other hand oftentimes emit toxic substances. Incorporation of polystyrene based resin has been reported to reduce the emission of toxic substances and moisture uptake due to the hydrophobicity of polystyrene. These properties of polystyrene when incorporated in composite  production may enhance the mechanical properties (Osemeahon and Dimas, 2014). This is more so since the deployment of polystyrene based resins in the production of polymer composites seems a sustainable practice of utilizing polystyrene and wood wastes. The effect of polystyrene based resins on properties of composites products made from Nigerian grown wood species is sparse in literature. Therefore, this work examined the strength and sorption properties of polystyrene based polymer composites made from Teak ( Tectona grandis ) and Mahogany (  Khaya ivorensis ) wood particles.   Arid Zone Journal of Engineering, Technology and Environment, June, 2018; Vol. 14(2):201-207. ISSN 1596-2490; e-ISSN 2545-5818; www.azojete.com.ng  2.0 Materials and Methods  Wood particles of Teak ( Tectona grandis ) and Mahogany ( khaya ivorensis ) were obtained from a local sawmill in Ibadan while polystyrene foams (PS) were collected within the premises of University of Ibadan Campus, Oyo State, Nigeria. 2.1 Board Formation and Testing  The particles of the wood species were air-dried for 2-weeks until 10% moisture content was attained. The dried particles were then sieved with a sieve of size 4.76mm. Particles that passed through the 4.76mm sieve were collected and used for the board formation. The collected PS were cleaned, cut into smaller sizes of about 2 x 2 x 5 cm³ and then dissolved in Premium motor spirit (PMS) in the PS: PMS ratio of 1:2 (w/v) based on the preliminary trails until homogeneous slurry was formed. Particles of the wood species were mixed with PS-PMS blends in the ratios 1:1, 2:1, 1:2 and 3:1, and formed into a board in a wooden deckle measuring 30 x 30 x 10 cm³. The mat was cold  pressed with a pressure of 3MPa for 30 minutes and then conditioned at room temperature (25 ± 2°) and at relative humidity of 72% for 14 days. 2.2 Fourier Transform Infrared Radioscopy (FTIR) of the Polystyrene Glue  The functional groups of the PS glue were determined using the Fourier transform infrared (FTIR) machine in accordance with the procedure adapted by Fabiyi et al. (2009). 2mg weight of the dried glue were homogenized with 200mg of Potassium bromated (KBR) salt. With the aid of hydraulic  press, the powdered mixtures were pelletized in disc form and inserted into the FTIR machine. Spectrum was taken as an average of 64 scans at a resolution of 4 cm -1 . 2.3 Flexural Test The de-moulded boards were cut to samples sizes according to ASTM standard (D790-07) and tested on a Universal Testing Machine (UTM) at cross head speed of 2mm/min from which the mechanical  properties i.e. moduli of rupture (MOR) and elasticity (MOE) were evaluated. 2.4 Water Absorption (WA) and Thickness Swelling (TS) Test Samples of the Teak and Mahogany bonded boards were initially weighed and then soaked in water at room temperature for 2 hours and then 24, 48 and 72 hours. At the end of the soaking period the samples were withdrawn from water and allowed to drain before the final weights and thicknesses were determine. The WA and TS of the wood species were determined as expressions of the initial weights and thicknesses. W.A. =       112 W W W    x 100% ……………………..(1)  while the thickness swelling (T.S) was expressed as a percentage of the srcinal thickness as T.S =       112 T T T    x 100% …………………………(2)  Where: W 1  is the initial weight W 2  is the final weight T 1  is the initial thickness T 2  is the final thickness   Adefisan, Evaluation of Strength and Sorption Properties of Polystyrene Bonded Composites of Mahogany (Khaya ivorensis) and Teak (Tectona grandis) Woods. AZOJETE, 14(2):169-171 ISSN 1596-2490; e-ISSN 2545-5818, www.azojete.com.ng  203 3.0   Results and Discussi on  3.1 The Infrared Radioscopy Analyses The infrared spectrum of the PS glue showed absorption bands at 3441 cm -1 corresponding to O-H stretching vibration which indicates the ability of the glue to bond with other substances (Table 1). The aromatic C-H stretching vibration of which occurred at 3062.85 cm -1 and 3027.62 cm -1  induces strength and abrasion properties. The saturated C-H vibration occurred at 2921.8 cm -1  while 1677.46 corresponds to the C=C stretching vibration. The peaks at 1600.51, 1600.29 and 1446.40 cm -1 are assigned to C=C stretching of phenyl group. The C-H deformation vibration band of benzene ring hydrogen occurred at 754.74 cm -1 and ring deformation was observed at 690.08 cm -1 (Osemeahon and Dimas 2014) 3.2 Density The densities of the Mahogany (  K. ivorensis ) and Teak ( T. grandis ) composites were between 379.8 and 780.3 kg/m 3  and 341.9 and 635.1 kg/m 3  respectively (Table 2). These values indicate that the composites are lightweight / medium weight products. Statistical analyses (Duncan’s multiple range test) revealed that the mixing ratio and wood species significantly (P ≤ 0.05) affected the dens ities of the composites (Table 2). Boards bonded with higher mixing ratios of polystyrene recorded significantly higher densities (Table 2). What this suggests is that increasing the glue content during  board production improved the interfacial bonding between the wood particles. Also, composites  bonded with Mahogany particles had significantly higher densities than those of Teak suggesting higher strength properties. Table 1: Infrared bands observed in Polystyrene Glue   S / N Wave number (cm-1) Peak Assignment 1 3441 O-H stretching vibration 2 3062.85 Aromatic C-H stretching vibration 3 3027.62 4 2921.8 Saturated C-H stretching vibration 5 1677.46 C=C stretching vibration 6 1467.04 C=C stretching vibration of Phenyl group 7 1600.51 8 1600.29 9 754.74 C-H stretching Vibration 10 690.08 C-H stretching Vibration 3.3 Mechanical Properties  The results of the flexural tests are shown in Table 2. As shown, the MORs of the Mahogany and Teak composites ranged from 4.9 to 12.9 N/mm 2  and 4.9 to 8.4 N/mm 2  respectively. The respective MOEs were between 1497 and 14,411 N/mm 2  and 23,746 and 77,249 N/mm 2  respectively. The MORs obtained in this study were lower than 15.1 to 24.1 N/mm 2  recommended by Forest Products Laboratory (FPL) (Cai and Ross, 2010) and 14.5 to 32 N/mm 2  obtained by Kosonen et al.,  (2000) and Voulgardis et al  ., (2003). The recorded MOEs were however comparable with those recommended by FPL (2,800  –   4,100 N/mm 2 ) and those obtained by Kosonen et al.,  (2000) and Voulgardis et al  ., (2003). The flexural test revealed that the fabricated boards have moderate strength values and can only be used as insulating components such as ceiling boards and panel products. The   Arid Zone Journal of Engineering, Technology and Environment, June, 2018; Vol. 14(2):201-207. ISSN 1596-2490; e-ISSN 2545-5818; www.azojete.com.ng  low flexural properties may be attributed to the low density profiles of the fabricated boards. Generally, boards with higher densities and higher mixing ratio recorded higher MORs and MOEs. This may be due to the enhanced interfacial bonding between the wood particles with increasing glue content. Statistical analyses ( Duncan’s multiple range test) revealed that the mixing ratio and the wood species significantly (P ≤ 0.05) affected the MORs and MOEs of the composites (Table 3). Also, composites fabricated with Mahogany particles recorded higher MOR than those of Teak. This may be possibly due to the higher density profiles of the Mahogany composites in comparison with those of Teak. As shown in Tables 2 and 3, the deployment of 2:1 mixing ratio in the composites  production seemed to yield the optimum flexural properties.  Table 2: Physical and Flexural Properties of Mahogany and Teak Composites Mixing ratio Density (Kg/m 3 ) MOR (N/mm 2 ) MOE (N/mm 2 )   Mahogany Composites   1:1 379.8 ef   (22.1) 4.9 g  (0.0) 1,497 e  (385.6)   1:2 368.2 ef   (6.6) 7.4 c  (0.04) 3,196 de  (1138.2)   2:1 570.7 c  (23.1) 12.9 a  (0.05) 8,106 d  (30.1)   3:1 780.3 a  (12.0) 5.2 f   (0.03) 14,411 c  (78.7)   Teak Composites   1:1 341.9 f   (37.7) 4.9 g  (0.0) 24,847  b  (2255.9)   1:2 406.8 e  (3.1) 7.1 d  (0.02) 28,824  b  (72.1)   2:1 520.3 d  (34.4) 8.4  b  (0.02) 77,249 a  (7998.6)   3:1 635.1  b  (41.8) 5.2 e  (0.01) 23,746  b  (1679.8)   Means with the same letters and columns are not statistically different * Significant at 5% level of probability Table 3: Duncan’s Test of the effect of Wood Species, Glu e Type and Mixing Ratio on the Density, MOR and MOE of Mahogany and Teak Composites Wood Species Density (kg/m 3 ) MOR (N/mm 2 ) MOE (N/mm 2 )   Mahogany 524.7 a (176.1) 7.6 a (3.33) 6,803.0  b  (526.6)   Teak 476.0  b (120.2) 6.4  b  (1.41) 38,666.0 a  (2362.7)   Mixing Ratio   1:1 360.9 c (34.5) 4.9 d  (0.0) 13,17.2 c  (1287.0)   1:2 387.5 c (21.6) 7.2  b  ( 0.14 ) 1,601.0  bc  (1405.5)   2:1 545.5  b (38.0) 10.6 a  (2.47) 4,267.8 a (3820.7)   3:1 707.7 a (84.2) 5.4 c  (0.18) 1,907.8  b  (522.2)   Means with the same Letters and in the columns are not statistically different * Significant at 5% Probability level 3.4 Sorption Properties  The results of the Water Absorption (WA) and Thickness Swelling (TS) are shown in Tables 4 and 5. As shown, the WA after 2 h and then 72 h soak in water ranged from 2.2 to 104.5% and 3.8 to 140% for the Mahogany and Teak composites respectively. The respective TS were 0.5 to 4.9% and 0.3 to   Adefisan, Evaluation of Strength and Sorption Properties of Polystyrene Bonded Composites of Mahogany (Khaya ivorensis) and Teak (Tectona grandis) Woods. AZOJETE, 14(2):169-171 ISSN 1596-2490; e-ISSN 2545-5818, www.azojete.com.ng  205 5.2%. These values compared favourably with those of Voulgardis et al  ., (2003). Results of the WA and TS showed that the composites had high sorption properties and cannot be used in outdoor applications. However, statistical analyses (Duncan’s Test, Table 6) revealed that the soaking time, wood species and mixing ratios significantly (P ≤ 0.05) affected the WA of the composites. Table 4: Water Absorption of Polystyrene Based Mahogany and Teak Composites   Mixing Ratio Water Absorption (%)   2h 24h 48h 72h   Mahogany Composites   1:1 61.5 fg  (8.4) 89.8 cde  (19.0) 96.2 cd  (17.0) 104.5 c  (10.9)   1:2 49.0 g  (7.8) 74.0 ef   (4.4) 78.2 e (12.3) 95.7 cd  (5.7)   2:1 13.2 ijklm  (2.5) 22.9 hij  (1.3) 24.8 hi  (1.2) 30.3 h  (3.2)   3:1 2.2 m  (1.0) 4.6 klm  (0.7) 6.6  jklm  (0.9) 9.3  jklmi  (1.4)   Teak Composites   1:1 47.4 g  (9.1) 122.5  b (11.8) 132.7 ab  (16.3) 140.0 a  (10.2)   1:2 49.0 g  (0.3) 75.2 ef   (0.8) 82.2 de  (0.9) 97.2 cd  (1.1)   2:1 21.2 hijk   (15.0) 48.5 g (15.6) 51.0 g  (14.0) 59.2 fg  (16.3)   3:1 3.8 lm  (0.5) 12.0 ijklm  (4.6) 19.6 hijkl  (0.8) 25.1 hi  (1.1)   * Means with the same Letters and in the columns are not statistically different * Significant at 5% Probability level Table 5 : Thickness Swelling of Polystyrene Based Mahogany and Teak Composites   Mixing Ratio Thickness Swelling (%)   2h 24h 48h 72h   Mahogany Composites   1:1 0.9 fgh  (1.4) 1.8 defgh  (2.6) 3.2 cdefgh  (3.7) 4.8 abcde  (3.4)   1:2 1.1 fgh  (0.9) 1.5 efgh  (1.1) 2.0 cdefgh  (1.2) 4.1 abcdef   (3.2)   2:1 4.9 abcde  (2.3) 5.4 abc  (2.3) 6.1 ab  (2.8) 7.1 a  (2.2)   3:1 0.5 gh  (0.3) 0.9 fgh  (0.6) 1.9 defgh  0.7) 3.7 cdefgh  (2.6)   Teak Composites   1:1 0.8 fgh  (0.1) 1.5 fgh  (0.07) 1.9 defgh  (0.01) 4.0 abcdefg  (0.1)   1:2 1.1 fgh  (0.5) 2.7 cdefgh  (0.8) 3.2  bcdefgh  (1.5) 3.6  bcdefgh  (1.5)   2:1 1.9 cdefgh  (1.4) 2.5 cdefgh  (1.4) 2.8  bcdefgh  (1.3) 3.7  bcdefgh  (2.1)   3:1 0.3 h (0.2) 1.7 efgh  (0.7) 3.5  bcdefgh  (0.9) 5.2 abcd  (1.0)   *Means with the same Letters and in the columns are not statistically different *Significant at 5% Probability level
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