By: Maria Teresa Cidade
From: Univ. Nova Lisboa
At: Complexo Interdisciplinar, B1-01
Melt viscosity is a crucial property in polymer science and technology. Its dependence on shear rate as well as on temperature has been thoroughly described and considered in formulations and predictions of the flow behaviour. Pressure effects, on the other hand, are usually an overlooked aspect of the flow properties of polymeric materials. However, typical pressure levels encountered during polymer processing operations, especially in injection moulding, can be very high (of the order of several tens of MPa), which justifies an effort to investigate this dependency. This presentation will be divided in two parts; in the first one, some basic concepts of rheology, including instrumentation, will be presented. In the second part, which gives the title of this presentation, a combined analysis of Pressure-Volume-Temperature, PVT, and rheological measurements, will be presented, in order to determine the pressure dependency of the viscosity of blends of a thermoplastic, polypropylene (PP), with a liquid crystalline polymer, a copolymer consisting of 60 wt% hydroxybenzoic acid and 40 wt% of polyethyleneterephtalate, commercially know as Rodrun LC3000. This combined analysis is, for the first time, applied to not only polymer blends but also to liquid crystalline polymers.