Ethylene-styrene interpolymers processability

As a result of the catalyst and process conditions used in their manufacture, the particular copolymers of current major interest are atactic, and contain typically up to about 50 mol% ( 80 wt%) styrene. These materials have been described as pseudo-random , since successive head-to-tail styrene chain insertions have been shown to be absent, even at high levels of styrene incorporation [1,2]. The term ethylene-styrene interpolymer (ESI) is used here to describe the specific ethylene-styrene copolymers produced via INSITE Technology. For convenience, all subsequent comonomer contents are expressed in weight percentages, unless otherwise stated. For example, the code ES70 refers to an interpolymer having 70 wt.% comonomer styrene incorporation. 

Ethylene-styrene interpolymers exhibit a novel balance of properties that are uniquely different from polyethylenes and polystyrenes. In contrast to other ethylene-a-olefin copolymers, ESI display a broad range of material response ranging from semicrystalline, through elastomeric to amorphous. The styrenic functionality and unique molecular architecture of ESI are postulated to be the basis of the versatile material attributes such as processability (shear thinning, melt strength and thermal stability), viscoelastic properties, low-temperature toughness and broad compatibility with other polymers, fillers and low molecular weight materials. 

Since the early 1990s, the constrained geometry metallocene catalysts have been used by Dow to produce either alternating or pseudo-random ethylene-co-styrene interpolymers (ESI) (Stevens et al. 1991). ESI with up to 50 wt% styrene is semicrystalline it is known to compatibilized PE/PS blends since it forms domain structures into which the homopolymers can dissolve. ESI also has good melt strength, mechanical, impact, and damping characteristics (Ellebrach and Chum 1998). Flow and processing information on ESI were pubUshed (Karjala et al. 1998). 

These interpolymers based on ethylene and styrene are an integral part of an exciting new generic class of materials, offering unique opportunities for innovative developments in basic polymer chemistry, catalyst and process development, materials science and engineering and application technology. 

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