Heterochain entanglements forced by shear forces and their influence on the properties of polylactic acid/hydrogenated styrene‐ethylene‐butylene‐styrene tri‐block copolymers blends

Abstract A forced entanglement between polylactic acid (PLA) chains and hydrogenated styrene‐ethylene‐butylene‐styrene (SEBS) tri‐block copolymers chains is designed based on the inertia of PLA to shear force and the sensitivity of SEBS to shear force. The melt blending of PLA with SEBS prepared through a twin‐screw extruder is a strategic method to form interchain entanglements. The influence of star‐shaped SEBS ( s ‐SEBS) and linear SEBS ( l ‐SEBS) on the compatibility, crystallization behavior, tensile properties, and rheological characteristics is systematically investigated. The incompatible interfaces between PLA and s ‐SEBS or l ‐SEBS are confirmed by their interfacial tension and micrographs of their cryo‐fractured surfaces. Although the interfacial incompatibility in PLA/ s ‐SEBS blends and PLA/ l ‐SEBS blends, s ‐SEBS, or l ‐SEBS could effectively enhance their crystallization behavior, tensile ductility and dynamic rheological properties. Relative to the Newtonian behavior of PLA, PLA/SEBS blends exhibit obvious shear‐thinning behavior under frequency‐dependent conditions, which clarifies the physical entanglements of PLA/SEBS blends. PLA/ s ‐SEBS blends possess stronger heterogeneous entanglements than PLA/ l ‐SEBS blends, which is verified by the micrographs of cryo‐fractured surfaces, crystallization characteristics, and rheological behavior. This designed concept based on the chain dynamics in the processing provides clues for polymer blends with significantly different sensitivity of chains to shear force to improve their properties. Highlights The melt blending of PLA with SEBS prepared through a twin‐screw extruder. The forced entanglement between PLA chain and SEBS chain is designed. PLA/ s ‐SEBS blends have stronger heterogeneous entanglement. The addition of SEBS can enhance its crystallization behavior and toughness. PLA/SEBS blends exhibit show shear‐thinning behavior in frequency dependence.