Design, validation and implementation of on-line measurement techniques to study the phase behavior of partially miscible PMMA/P(alpha)MSAN blends under quiescent and flow conditions, and application to filled-PVC in quiescent mode.

摘要

In this dissertation, temperature and flow effects on the phase behavior of a polymer blend were investigated by means of the Raman spectroscopy technique, while the ultrasonic technique was implemented only under static conditions. A static bench setup and a flow cell were used in the implementation processes. The polymer systems used for experimentation included homopolymer poly(methyl methacrylate)(PMMA), random copolymer poly(α-methyl styrene-co-acrylonitrile)(PαMSAN), their partially miscible blends, and a commercial PVC compound filled with calcium carbonate.; Raman spectroscopy was applied to investigate the phase behavior of the partially miscible polymer blend of PMMA and PαMSAN under static and flow conditions. Then, the effects of simple shear flow on the phase behavior of this blend, starting from the two-phase region, were undertaken in a simple capillary flow, backed up by the examination of the extrudate by optical and electron microscopy techniques. The ultrasonic studies involved investigating the temperature dependence of the ultrasonic velocity and attenuation under static conditions, using the materials mentioned above.; The cloud point curve for the solution-cast blend was established by heating at various rates with light scattering. Furthermore, the cloud point curve for selected melt-blended static samples using Raman spectroscopy was established to serve as a benchmark for the flow experiments.; The static ultrasound technique was able to detect composition dependence of the attenuation peak as a function of temperature, but, it was not able to detect the onset of phase separation in the blends tested. The setup and procedures were used to follow the filler loading and sizes effects in a calcium carbonate filled PVC compound, giving a good composition and filler size dependency of the attenuation property.; The effects of shear flow on the onset of phase transition (dissolution) using a flow cell designed with slit conduit that is equipped with flush mounted pressure transducers, was monitored by Raman spectroscopy detection system through the recording of the background Raman scattering. It was found that at temperatures of 190, 200 and 220°C, for 90/10 PαMSAN/PMMA blend at low shear rates, the shear heating effects due to high viscosity of the blend, seems to be overpowering any flow effect that would have precipitated phase changes towards 1- or 2-phase.; Lastly, we probed the effect of shear flow on the phase behavior of the blend in a simple capillary die with an L/D ratio of 28.5 (D = 0.063in.), backed up by microscopic spatial analysis of the extrudate cross sectional features. Un-polarized optical images of the flow cross section suggests radial variation in the morphology as melt temperature is set deeper into the 2-phase region, which is undesirable as such a trend points in the direction of poor property in any article made there-from. The sampling of the morphology near the region of high stress, at melt temperatures close to the cloud points, produced morphological trends similar to that of a partially miscible blend in a quiescent state as the temperature is being raised.