Where there is a need for clarity, flexibility, elasticity, and reduced stress whitening with improved toughness and impact strength, ExxonMobil Chemical (Houston, TX) offers compounders a minority blend partner in the form of new Vistamaxx specialty elastomers. They show excellent compatibility with polypropylene (PP) and polyethylene (PE), and compounding costs can be reduced when substituting Vistamaxx for polymers, including styrene block copolymers.
A predominantly amorphous ethylene propylene matrix laced with well-dispersed isostatic PP crystallites delivers elasticity, flexibility, and impact toughness while maintaining clarity in PP random copolymer and PP homopolymer blends.
The higher the concentration level of Vistamaxx, the better the physical properties. When the elastomer content is greater than 30%, there is a steep increase of elongation at break, and impact strength in even small additions of the elastomer are improved down to temperatures of -20°C. Thermal properties in blends with a Vistamaxx content of less than 30% are dominated by those of the PP; however, note that with a blend of more than 30%, stickiness is observed when aged at temperatures higher than 100°C. On the other hand, stress whitening is eliminated.
Its unique compatibility with PP, plus its oil and filler loading capabilities, make Vistamaxx also an ideal component for styrene ethylbutylene styrene (SEBS) compound modification. Vistamaxx acts as a plasticizer in SEBS compounds, increasing tensile and tear strength by up to 45%, while reducing raw material costs by replacing the SEBS resin. Blend density also has a significant influence on chemical resistance, but Vistamaxx elastomers show excellent chemical resistance to aqueous systems and nonhydrocarbon-based fluids.