RHEOLOGICAL, MECHANICAL, AND ADHESIVE PROPERTIES OF THERMOPLASTIC-LCPBLENDS FILLED BY GLASS-FIBERS

Rheological, mechanical, and adhesive properties have been studied of two-phase polymer blends containing a liquid crystal copolyester of po ly(ethylelene terephthalate) and p-hydroxybenzoic acid plus isotactic polypropylene (PP) with varying compositions and concentrations of gla ss fibers. Perfect fibrillation of the disperse LC-phase into the PP-m atrix in capillary flow was observed at LCP concentrations >20 wt% and temperatures >488 K. This effect leads to a decrease of blend viscosi ty and a reinforcing of the extrudate's mechanical characteristics. At the same time, more essential reinforcement is achieved by the simult aneous addition of the reinforcing agents both of the LCP and glass fi bers. Processing of PP is not impaired. It was found that the adhesive strength increases substantially when the amount of LCP in the blend exceeds a definite level, corresponding to a phase inversion. The resu lts are explained by the formation near the interface of two adhesion layers: the first is composed of pure LCP having a higher surface tens ion, whereas the second layer represents the blend of various composit ions. At small amounts of LCP, the adhesion failure proceeds in the in terphase between the LCP and the blend. After the phase inversion, whe re adhesion strongly increases, the failure of adhesion joints proceed s near the interface between LCP and the glass.