EFFECT OF EPDM ON LDPE LLDPE BLENDS - MECHANICAL-PROPERTIES/

Blends of two polyethylenes and an elastomer were prepared to investig ate the effect of the latter polymer. The blends contain equal parts o f low density (LDPE) and linear low density polyethylene (LLDPE), and ethylene-propylene-diene rubber (EPDM) with variable content ranging f rom 0 to 17.5%. Melt-mixed blends were prepared using a single-screw e xtruder. The influence on the mechanical properties of the following f actors were analysed: EPDM content, stretching rate in the range from 10 to 750 mm/min, and two cooling conditions. From the equilibrium tor que the miscibility was analysed. The structure exhibited by the stres s-strain (sigma-epsilon) curve of the polyethylenes blend is reduced w ith the addition of the elastomeric phase, and the ultimate properties increase because the amorphous phase becomes softer and reduces its c apability to transmit the applied stress to the crystalline particles. The slope of the sigma-epsilon curve in the strain hardening region s hows a maximum value at the stretching rate similar to 50-80 mm/min, w hich is explained partially in terms of the strain-induced crystalliza tion of the polyethylene components. (C) 1997 John Wiley & Sons, Inc.