Enzymatic degradation of poly ( ε-caprolactone), poly (vinyl acetate) and their blends by lipases

Abstract

Poly ( ε-caprolactone) (PCL) and poly (vinyl acetate) (PVAc) and their blends were degraded in toluene by two lipases (Novozym 435 and Candida Rugosa) at 60°C. The degradation of PCL and side-chain hydrolysis of PVAc yielded specific products of molecular weight ∼500 and ∼700, respectively. FTIR analysis of the polymer before and after enzyme treatment and the specific products show that there is large reduction of ester linkages and generation of –OH, –COO (−), –COOH groups in the broken chains. The optimal temperature for the side-chain hydrolysis of PVAc was 60 and 65°C and the optimal temperature for the biodegradation of PCL was 55 and 60°C for Candida Rugosa and Novozym 435, respectively. Continuous distribution kinetics was proposed for determining the rate coefficients of the polymers and deactivation of the enzyme. Enzymatic degradation studies of PCL–PVAc blends showed that there is a drastic reduction in the degradation of PCL in the blends. This was modeled by the interaction between polymers.