FREE-RADICAL BRANCHING OF POLYLACTIDE BY REACTIVE EXTRUSION

The reactive extrusion of polylactide (PLA) with a free radical initia tor resulting in a branched polymer was accomplished. Reaction conditi ons were in the range of 160 degrees C to 200 degrees C with an initia tor concentration between 0.0 and 0.5%. Triple detector size exclusion chromatography, melt flow index, thermal gravimetric analysis, differ ential scanning calorimetry, and dynamic mechanical analysis were used to characterize the polylactide polymers. PLA without initiator showe d extensive degradation as was evidenced by a decrease in both molecul ar weight and melt viscosity. The optimum range for branching resultin g in a high molecular weight and low melt flow index polylactide was f ound to be around 170 degrees C to 180 degrees C and 0.1 to 0.25% init iator.