impact, thermal and biodegradation properties of high impact polystyrene/corn starch blends processed via melt extrusion

High impact polystyrene (hips)/corn starch blends were prepared in presence of glycerol as a plasticizer via melt extrusion process by a twin-screw extruder. the novelty of this work is the use of pre-gelatinized corn starch which is a new modified corn starch. in addition, the procedure of making blends by extruder is easy and practical from the industrial point of view. the blends were then characterized by scanning electron microscopy (sem) to visualize their morphology and dispersion of starch in hips matrix, soil burial test (sbt) to investigate blend biodegradability by measuring weight loss of samples, izod impact strength test to evaluate impact properties, and melt flow index (mfi), thermo-gravimetric analysis (tga) and vicat softening point (vsp) tests to evaluate their thermal properties. the results indicated that these properties were affected by the amount of starch and glycerol used for preparation of blends in a way that the addition of starch and glycerol led to a faster degradation rate especially in the first two weeks, more decomposition stages, and a decrease in the values of izod impact strength and vsp. measurements also showed that higher amount of starch led to a decrease in the value of melt flow rate (mfr), although it was increased by addition of glycerol.