Plastic waste is a serious environmental problem and become an enormous challenge to waste management. A high determination to produce eco-friendly polymer has led the researchers to investigate about biodegradable polymers by adding natural polymer into the non-degradable plastic material. Thermoplastic is a material that produced by incorporating the plasticizer into the natural polymer, ie starch. Therefore in this research, an attempt was made by incorporating protein based natural polymer which was soya spent powder (SSP) into LDPE matrix. This study investigated the influence of glycerol on the properties of blends prepared from low density polyethylene (LDPE) with different SSP content varied from 5 to 25 wt%. Spear grass powder as a natural pro-oxidant (1.5 wt%) has been added into LDPE/SSP and LDPE/TSSP blends. Natural weathering test and soil burial test were performed for 9 months period to determine the potential of this polymer to degrade in different surroundings. As a result, LDPE/TSSP blends showed higher strength and elongation at break (Eb) compared to LDPE/SSP blends after weathering and composting. However, after the addition of spear grass powder, the tensile strength and Eb of LDPE/TSSP blends decreased. Scanning electron microscopy (SEM) micrographs showed the formation of crack, pores and fungus colonization on of LDPE/SSP and LDPE/TSSP blends surfaces. For differential scanning calorimetry (DSC) analysis, LDPE/TSSP blends presented higher crystallinity (15.65% for 25 wt% TSSP) compared to LDPE/SSP blends for the same blends ratio (14.76%). The thermal stability for each blends decreased from 451 °C (for neat LDPE) with an increase of 25 wt% of SSP (269 °C) and TSSP (284 °C) content. Three different strains have been successfully isolated in this study. Aspergillus fumigatus from the genus of Aspergillus encountered the highest percentage increment of cell dry weight (mg) which is 56% through the fermentation process.
