A green and biodegradable plasticizer from copolymers of poly(β‐hydroxybutyrate‐co‐ε‐caprolactone)

Abstract Biodegradable polymers such as poly(3‐hydroxybutyrate) (PHB) and polycaprolactone (PCL) blends are considered as potential replacements for non‐degradable polymers, however, their brittleness is an obstacle for their full realization in biomedicine and food packaging. Here, new biodegradable plasticizers are developed to improve the physicochemical properties of PHB and PCL blends. These plasticizers are synthesized through a one‐step random copolymerization process using different mass ratios (1:1, 2:1, 1:2) of β‐butyrolactone (HB) and ε‐caprolactone (CL) monomers. Plasticizer with larger content of CL segments (1:2) shows a thermal stability higher than other ratios. The addition of plasticizers to PHB/PCL blends enhances the elongation at the break of PHB 50 /PCL 50 blend at least 4 to 6‐fold compared to pure PHB. This process also decreases the melting point and crystallization of PHB/PCL blends which are pivotal for thermal processing, such as extrusion, while no adverse impact on the tensile strength and elastic modulus of blends was observed.