Effect of Wood Strength on the Properties of Wood Saw Dust Reinforced Polymer Matrix Composites

Abstract

The use of wood dust for reinforcing polymer has already been considerably studied both from a scientific and a commercial point of view over the last decades. Because, these materials are attractive for their reduced environmental pollution and globally pleasant aesthetical properties. Wood dust is attractive filler for thermoset polymers, mainly because of it low cost, low density and high-specific properties. It is biodegradable and nonabrasive during processing. The present research work has been undertaken with an objective to explore the effects of wood strength, i.e. the types of woods were used to prepare the dust particle as reinforcing materials in polymer composites. In this regards, mechanical, electrical and thermal behaviours of the resulting composites reinforced with dust particle of various woods were investigated. For more detail study 0, 5 and 10 wt% were used to know the effects of proportions of wood particle on composite properties. Similarly, wood particle of two different sizes (medium and coarse) were used to know the effects of wood particle sizes on the properties of the developed composites. Initiative has also been taken to investigate the effects of chemical treatment (treatment with 10% NaOH solution) of wood particle on composite properties. Among three woods Garjan, Kerosene and Gamari resulted, respectively, the highest, medium and the lowest tensile strengths. Experimental results revealed that saw dust particle of higher strength wood resulted relatively higher tensile strength of the developed composites. For all cases, tensile strengths of the developed composites were found to decrease with increase in the wood particle contents. Compared to medium size particle, coarse saw dust particle caused more deterioration in the tensile strengths. On the other hand, chemically treated wood particle resulted relatively higher strengths. With increase in the wood particle contents more wood particle stacking and air bubbles were found during the study of fracture surface under the SEM, which have been thought to be responsible for the reduced tensile strength of the composites. For pure woods, wood strengths or densities have not been found to influence their breakdown voltages. In this case, size of the individual pore was found to influence the breakdown voltage. Similar to tensile strength, breakdown voltage was found to decrease with increase in the proportion of the wood particle. FTIR results suggested that chemical treatment removed part of the lignin of the wood particle. Increase in the breakdown voltage of the composites reinforced xvii with the chemically treated wood particle suggested that lignin has relatively poor breakdown voltage compared to that of the wood fiber. Pure polyester has been found to have lower thermal conductivity compared to that of any wood and that wood strength or true density has been found to influence the thermal conductivity of the as-received pure very mildly. With increase in the dust particle content, thermal conductivities of all composites have been found to increase for both the untreated and chemically treated wood particle. Thermo-Gravimetric Analysis (TGA) was used to know the decomposition of composites as a function of increasing temperature. TGA results revealed that wood particle have no significant influence on the thermal stability of the pure polyester up to 350oC, however, the thermal stability of the composite increased slightly at further higher temperature. This high temperature thermal stability was again improved with higher proportion of wood particle. Chemical treatment improved the thermal stability of the composite. In this case improved thermal stability has been found from around 150oC. This observation suggested that lignin has lower thermal stability compared to that of wood fiber. Water absorption of both pure polyester and wood particle reinforced composites has been found to increase with increase in time. Either increase in the proportion of wood particle content in the composite or particle size of the wood dust increased the water absorption. Chemical treatment improved almost all properties. However, in the case of water absorption, it has been found to reduce the water absorption resistance of the composites, which indirectly suggest that lignin has better water absorption resistance than that of wood fiber.