Ternary blends from biodegradable poly(L-lactic acid), poly(ε-caprolactone) and poly(vinyl acetate) with balanced properties

A ternary blend of poly(L-lactic acid) (PLA), poly(e-caprolactone) (PCL) and poly(vinyl acetate) (PVAc) was melt compounded with an aim to obtain novel biodegradable blends with a balance of performance. We systematically studied the relationship between the microstructure and macroscopic properties of the ternary blends. PVAc was miscible with both PLA an PCL. It was interesting that PVAc was selectively located in the PLA matrix of PLA/PCL/PVAc ternary blends, which significantly affected the crystallization behavior, mechanical and rheological properties, and enzymatic hydrolysis rate of the blends. The inhibited crystallization of PLA was achieved, whereas the crystallization of PCL was not affected by incorporating PVAc. Unexpectedly, increases of 10%, 17% and 26% were achieved in the yield strength, breaking strength and modulus of the ternary blend with 20 wt% PVAc compared to PLA/PCL binary blend, while the elongation at break maintained above 300%. Moreover, the rheological properties was enhanced and enzymatic hydrolysis rate was decelerated by introduction of PVAc. The excellent stiffness - toughness balance coupled with the enhanced melt viscoelasticity of the blends will help to expand the property range and processing methods of biodegradable polymers.