Studies of the physico-mechanical properties of chemically treated wood fiber-reinforced polypropylene composites

Abstract

Wood plastic composites (WPCs) have been popular day by day in Bangladesh as well as in the whole world and have characteristics similar or close to commercial wood. In this research work, different types of soft wood reinforced polypropylene (PP) composites were prepared by injection moulding technique. To prepared improved sawdust-PP composites by chemical treatment, an innovative, clean, cheap and effective yet simple technology with different procedures was introduced in this work to demonstrate the suitability of wood plastic composites’ techniques for developing countries. The effects of treatments on the physico-mechanical properties of composites were studied. Untreated raw sawdust was modified by sodium hydroxide and the effect of alkali treated sawdust reinforced PP composites was studied comparing with the raw sawdust-PP composites. FT-IR spectroscopic analyses were done for chemical treatment and results showed the evidence of positive reactions. The effects of fiber content on the physico-mechanical properties of composites were studied by preparing the composites with different percentage of fiber loading (from 20 wt.% to 35 wt.%) for each type of composites. Mechanical properties; tensile strength, tensile modulus, elongation at break, flexural strength, flexural modulus and hardness were measured for both alkali treated sawdust-PP composites and raw sawdust-PP composites. Improved mechanical properties were obtained for most of the treated sawdust-PP composites over untreated raw sawdust-PP composites. Thermal analysis was done with the fractured part of the composite specimens and increased thermal stability was found for alkali treated sawdust-PP composites compared to that of raw sawdust-PP composites. Scanning Electron Microscopy (SEM) and water absorption test were done to study the physical properties of both types of composites. SEM was taken to investigate the interfacial adhesion and bonding between the sawdust and PP matrix from various chemical treatments. Improved interfacial interactions were found for treated composites than untreated composites. Water absorption tests were carried out of all composites to investigate the effect of chemical treatment on the moisture absorption characteristics of hydrophilic sawdust in sawdust-PP composites which has direct effect on the dimensional stability of the composites. Reduced water absorption was found for alkali treated sawdust-PP composites. All the findings are reported in details in this thesis.