Low melt flow visbroken hydrogenated styrenic block copolymers

Abstract

This invention discloses a viscosity-reducing cracked hydrogenated styrene block copolymer (m-HSBC). The polymer comprises at least one vinyl aromatic block S and at least one rubbery block R derived from a hydrogenated diene unit. The viscosity-reducing cracked HSBC is prepared by controlled chain scission of a high molecular weight HSBC precursor while maintaining a GPC main peak molecular weight (Mp) >200 kg / mol. When measured at 190 °C under a 2.16 kg load, the viscosity-reducing cracked HSBC exhibits an extremely low melt flow rate (MFR) of <10 g / 10 min. This viscosity-reducing cracked HSBC balances controlled melt flow, elasticity, and mechanical integrity, making it particularly suitable for use in foams and foam-forming compositions.

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