Study of the biodegradability and thermal properties of wood-plastic composite obtained from wood flour, polyhydroxybutyrate and starch

The growing concern about environmental pollution has increased the demand for biodegradable materials worldwide. Natural polymers are used in composite manufacturing to prevent environmental damage, reduce costs, and replace synthetic polymers. In this research, the biodegradability and thermal properties of the wood-plastic composite were investigated. Beechwood flour with a weight ratio of 40 % and a particle size of 80 mesh was used to make the samples as a reinforcement of the matrix. The studied polymer to make the composite biodegradable was polyhydroxy butyrate (PHB). Starch with a weight percentage of 8 and 12 % was used as copolymer, nanoclay was used to improve properties, and maleic anhydride was used as a coupling agent. The samples were mixed using a twin-screw extruder and made with an injection machine. Then, they were subjected to thermogravimetric analysis, differential scanning calorimetry, and biodegradability tests. In terms of thermal properties, a degradation temperature of about 250 ºC was achieved with the presence of wood flour as a filler and other additives, which showed improvement compared to PHB biopolymer which is in the range of 95 ºC. The glass transition temperature increased and this value in the pure polymer was 5 and it showed an increase up to 68 degrees in the results obtained from the composite, however, the melting and crystallinity were decreased in both. In the biodegradable test, the samples containing PHB showed good degradability properties. The weight loss occurred due to the destruction of wood flour, starch, and natural polymer by soil microorganisms. The produced composite samples in this research are completely biodegradable.