PVT and oscillatory tests to analyze pressure effects on polypropylene/Rodrun LC3000 blends: Determination of the pressure dependency of the viscosity

A combined analysis of Pressure-Volume-Temperature (PVT), Dynamic Mechanical Thermal Analysis (DMTA) and oscillatory flow measurements for blends of a polypropylene (PP) with a commercial liquid crystalline polymer (Rodrun LC3000) is presented. This analysis allows the determination of the pressure-viscosity coefficient b = ∂lnη0/∂P. This coefficient depends on the Rodrun LC3000 content, increasing with it and is of the same order of magnitude as values reported for several commercial polymers showing a similar dependence of the viscosity on pressure. The analysis of the pressure dependence of Tg (related to b) leads to the conclusion that the number of segments involved in the glass transition of PP increases with the Rodrun LC3000 content, thus demonstrating that the polymers are not totally immiscible. As far as the authors know, this is the first time that the dependence of the viscosity on the pressure has been reported for thermoplastic/liquid crystalline polymer blends.