Martin J. Guest

A study of the blending of ethylene-styrene copolymers differing in the copolymer styrene content : Miscibility considerations

Blends of two or more ethylene–styrene (ES) copolymers that differed primarily in the comonomer composition of the copolymers were studied. Available thermodynamic models for copolymer–copolymer blends were utilized to determine the criteria for miscibility between two ES copolymers differing in styrene content and also between ES copolymers and the respective homopolymers, polystyrene and linear polyethylene. Model estimations were compared with experimental observations based primarily on melt-blended ES/ES systems, particularly via the analysis of the glass-transition (Tg ) behavior from differential scanning calorimetry (DSC) and solid-state dynamic mechanical spectroscopy. The critical comonomer difference in the styrene content at which phase separation occurred was estimated to be about 10 wt % for ES copolymers with a molecular weight of about 105 and was in general agreement with the experimental observations. The range of ES copolymers that could be produced by the variation of the comonomer content allowed the study of blends with amorphous and semicrystalline components. Crystallinity differences for the blends, as determined by DSC, appeared to be related to the overlapping of the Tg of the amorphous component with the melting range of the semicrystalline component and/or the reduction in the mobility of the amorphous phase due to the presence of the higher Tg of the amorphous blend component.

- Blends of Ethylene/Styrene Interpolymers and Other Polymers: Benefits in Applications

INSITE™ technology has enabled the synthesis of ethylene/styrene interpolymers (ESI) using single site constrained geometry catalysts. The current focus is on ESI containing up to about 50 mole % (∼ 80 wt%) copolymer styrene content. These ESIs encompass materials ranging from crystalline to amorphous microstructure, dependent upon the copolymer styrene content. Materials engineering through blending of ESIs with other thermoplastic polymers can be used to expand the material performance envelope, and design materials to meet specific performance requirements. The performance requirements of potential applications currently under development for ESI can be met by thermoplastic blends with one or more thermoplastic polymers. ESIs exhibit compatibility with a wide range of polymers because of their inherent combination of olefinic and styrenic functionality. Blends of ESI with PS, PE, and PP, in particular, have been found to offer interesting and unique combinations of performance properties. The selection of blend components, blend composition ratio and final part fabrication conditions are key factors in determining structure/property relationships. Appropriate morphology/rheology modeling is useful in blend design.

Melt Rheology and Processability of Ethylene/Styrene Interpolymers

The melt rheology and processing characteristics of ethylene/styrene interpolymers, ESI, are correlated with the styrene content and molecular weight of the interpolymers. The complex viscosity, mastercurves, activation energy, high shear rate processability, and melt strength are discussed for four well-defined ESI. Comparisons are also made to polyethylene and polystyrene where appropriate.