Highly toughened polylactide/epoxidized poly(styrene-b-butadiene-b-styrene) blends with excellent tensile performance

Polylactide (PLA) has inherent shortcomings which limit its widespread application: brittleness, low elongation and low melt strength. In this paper, these problems were addressed through melt blending of PLA with an epoxidized thermoplastic elastomer, epoxidized poly(styrene-b-butadiene-b-styrene) (ESBS). ESBS with different epoxidation degree were prepared by an in-situ peroxy-formic acid method. The T-g of ESBS increased while the flexibility decreased with increasing epoxidation degree. The impact strength improved from 29.9 J/m for pure PLA to 891.0 J/m for the blend with 30 wt% ESBS35.8%, meanwhile, the elongation at break increased from 3.5% to 253.8%. In-situ compatibilization of these immiscible blends was achieved via melt blending of PLA with ESBS that led to the formation of graft copolymer architecture at the interface. The compatibility between PLA matrix and ESBS phase increased gradually while the notched impact strength increased firstly and then decreased with increasing epoxidation degree of ESBS. The morphology of PLA/ESBS blends played an important role in notched impact strength and could be controlled by adjusting the epoxidation degree of ESBS. Rheological tests showed a drastic enhancement of melt viscosities for PLA/ESBS blends in oscillatory experiments. Therefore, the mechanical properties could be easily tailored by the epoxidation degree of ESBS. (C) 2016 Elsevier Ltd. All rights reserved.