Blending of poly(L-lactic acid) with poly(cis-1,4-isoprene)

Poly(L-lactic acid) (PLLA), a brittle biodegradable thermoplastic polymer, was blended with rubbery poly(cis-1,4-isoprene) (PIP). The PLLA/PIP blend, however, was incompatible as indicated by two Tg’s, each stemming from PLLA and PIP domains, respectively. Since PLLA was known to be compatible with poly(vinyl acetate) (PVAc), PIP was grafted with vinyl acetate monomer to form PIP-g-PVAc, which was then blended with PLLA. The blend of PLLA and PIP-g-PVAc had two Tg’s. The lower Tg, which was due to PIP phase, did not vary with the blend composition, while the higher Tg, which was due to PLLA rich phase, decreased with an increase in the graft copolymer content. The PVAc moiety of the graft copolymer seems to have been mixed in with PLLA. The tensile properties of the PLLA/PIP-g-PVAc blend were much superior to those of the PLLA/PIP blend.