Optimization studies of blend composition and ageing parameters for makingLDPE/HDPE/LLDPE films by response surface methodology

Films of low-density (LD), high-density (HD) and linear low-density (LLD) p olyethylenes have been prepared by melt blending in a single screw extruder (L/D ratio = 20:1). The film samples were aged at 50, 60, 70, 80, and 90 d egreesC for different time periods up to 750h. A central composite rotatabl e design (CCRD) has been adopted to study the effect of blend composition, ageing time and ageing temperature on tensile strength using response surfa ce methodology (RSM). Also, a linear second-order model has been developed to optimize and to study the interaction effects on tensile strength of the films. The optimized film sample had a maximum strength of 85.43 kg/cm(2) when aged at 70 degreesC for 333.5 h having 44.8, 27.7 and 27.7 wt.-% of LD PE, LLDPE and HDPE, respectively, in the blend system.