SynopsisAn experimental study of temperature effect and composition effect on the rheological and extrusion properties of several dispersed multiphase polymer melts were investigated, using a cone-and-plate rheometer and a capillary rheometer. The polymeric systems studied included three homopolymers (two polystyrenes and one poly(methy1 methacrylate) (PMMA)), a mechanically blended copolymer of polystyrene and PMMA, two graft copolymers (rubber-modified polystyrene and PMMA), and three particulate-filled polystyrenes (CaCO,, milled glass fiber, and glass flake). It was found that the principal normal stress difference plotted against shear stress gives rise to a temperature independence for all dispersed multiphase polymeric systems. Composition independent correlations, however, do not exist for the principal normal stress difference. The extrudate swell plotted against shear stress becomes independent of temperature only for the homopolymers and graft copolymers. For the mechanically blended polymers and particulate-filled polymers, the temperature independent correlation does not exist. The reduction in viscosity of the glass fiber-and glass flakefilled polystyrenes is found due to the degradation of the base polymer during mixing.

Interpenetrating polymer networks of polyurethane and unsaturated polyester were prepared by reaction injection molding (RIM) and transfer molding. The structures of the molded samples were analyzed by electron microscopy and dynamic mechanical analysis. It was found that polymer morphology and dynamic mechanical properties depend strongly on the molding temperature, reaction rate and reaction sequence. Simplified structure models based on Takayanagi's model and sample morphology can predict the storage modulus reasonably well but not the tans.

An experimental and theoretical study of reaction injection molding (RIM) of polyurea was conducted in this work. A lab‐scale RIM machine was used to carry out the polyurea bulk polymerizations. A “free‐table” viscometer was designed to measure the fast rheological changes and liquid‐solid transition. A mathematical model was proposed to simulate the fast reaction and rheological changes in the polyurea RIM process. The parameters of this model were determined based on the solution polymerization data from FTIR and Haake rheometer measurements. Combined with an appropriate heat transfer equation, this model predicts fairly well the adiabatic temperature and viscosity rises of bulk polyurea reactions in RIM.

SynopsisThe viscosity rise and conversion profile of polyurea reaction in solution were measured using a Haake viscometer and an FTIR, respectively. In a three-component polyurea system, it was found that the liquid-solid transition is dominated by the microphase separation from the formation of hard segments. The formation of soft segments mainly contributes to the initial viscosity buildup. A series of experiments were carried out to study the effects of resin composition, solvent concentration, and reaction temperature on the viscosity rise and gelation of polyureas.