Effects of Aspergillus niger on some Physical Properties of Composites Produced from Transparent Low Density Polyethylene Films/Iroko Wood Dust Particles

Abstract

Composites were prepared by dissolving low density polyethylene (LDPE) films and wood dust particles in toluene at 115 ^oC. The hardness, water absorption, weight loss, FT-IR spectroscopy and SEM of the composites were investigated before and after biodegradation. Generally, water absorption increased with increase in wood particles but decreased with increase in LDPE. This was attributed to the hydrophilic nature of wood and hydrophobicity of the plastic. However, un-used transparent LDPE films in composite showed decreased in amount of water absorbed by 15.7% after 2 hours and 8.5% after 24 hours whereas, waste transparent LDPE in composite gave 14.1% after 2 hours and 13.1% after 24 hours immersion. This was ascribed to the fact that the microorganisms have interacted with the both cellulosic and non -cellulosic components of Iroko wood dust particles thereby creating more -OH groups. This led to the high amount of water absorbed after degradation. Significant decrease in hardness was observed as the Iroko wood dust particles increased at constant LDPE but when LDPE films increased the hardness was however observed to increase at constant hard wood particles. This was attributed to the possible formation of strong interaction between LDPE/Iroko wood dust particles leading to more oriented and better packing of the composite. Both vLDPE and wLDPE composites showed decrease in weight as the time of degradation progresses. Their FT-IR spectra showed the presence of hydroxy, carbonyl and alkyne groups after biodegradation. The SEM mircographs of the composite showedthe growth of A. niger on the surfaces and in the cavities. A decrease in interfacial bonding was visible in composites with higher amount of Irokowood dust particles than with higher amount of LDPE films. The growth of microbes were viewed to be due to the presence of the Iroko wood fibre in the composite rather than the low density polyethylene films. Both the cellulosic and non-cellulosic content of wood could have served as the sources of nutrient for the growth of A. niger. Since the growth of A. niger did not affect these physical properties significantly. Therefore, materials produced such as wooden panel, chair, etc. for outdoor use many not experience significant destruction by the common mold.