Study of biodegradation evolution during composting of polyethylene-starch blends using scanning electron microscopy

The end product of low-density polyethylene-starch was manufactured by injection molding process. Four starch concentrations (10, 25, 40, and 50%) were used for blend preparations, which were injected into the mold of a 250 mL commercial cup. A control sample of neat polyethylene (PE) was also included. Square coupons (4 cm × 4 cm) of each blend were buried in the middle of a 50 cm pile of compost. Samples were recovered, washed, dried, and weighed after 25, 50, 75, 100, and 125 days beneath the compost. Scanning electron microscopy (SEM) analysis was performed on the samples to track the biodegradability evolution. A SEM scandium analyzer was used to measure the size and number of pores and the eroded area. Weight loss measurements were conducted to validate the SEM observations. Total biodegradation time was determined by mathematical analysis and graphical extrapolation. SEM analysis revealed the formation of pores, cavities, discontinuities, and cracks resulting from the time beneath the compost. Pore measurements revealed that the specimen composed of 40% starch and submerged for 125 days experienced up to 25% eroded area. Pure PE remained practically unchanged for the 125-day period. Fourier transform infrared spectroscopy studies also demonstrated the biodegradation of PE in PE-starch blends.