Effect of ethylene/propylene ratio on reinforcing characteristics of liquid crystalline polymer (LCP) in EPDM-LCP composites

摘要

Two ethylene/propylene diene monomer (EPDM) polymers wee blended with a liquid crystalline polymer (LCP) at concentrations of 10, 20, 30 and 40 wt-%. The effects of ethylene/propylene (EP) ratio on the in situ fibrillation, and hence the reinforcing characteristics, of the LCP in EPDM-LCP blends were studied. The fibre forming capacity of the LCP depended on the viscosity of the EPDM rubber. Under high temperature processing conditions (at 300 deg C), the high EP ratio EPDM, which had the higher viscosity, facilitated the fibrillation of the LCP. Further melt processing at 100 deg C, followed by curing at 150 deg C, decreased the reinforcing effects of the LCP owing to breakage of the fibrils under the high shear stresses developed in the high viscosity matrix. However, this degradation of fibre lengths depended on the LCP concentration. After curing, the more viscous EPDM formed blends with higher stiffanesses and strengths than growth of crystal domains in the EPDM matrix were promoted by small amounts of LCP. Again the effects were more pronounced in the EPDM with the higher EP ratio.