Influence of the 3-Hydroxyvalerate Content on the Processability, Nucleating and Blending Ability of Poly(3-Hydroxybutyrate--3-hydroxyvalerate)-Based Materials.

Poly(3-hydroxybutyrate--3-hydroxyvalerate (P(3HB--3HV) copolymers are an attractive class of biopolymers whose properties can be tailored by changing the 3-hydroxyvalerate monomer (3HV) concentration, offering the possibility of counteracting problems related to high crystallinity, brittleness, and processability. However, there are few studies about the effects of 3HV content on the processability of copolymers. The present study aims to provide new insights into the effect of 3HV content on the processing step including common practices like compounding, addition of nucleation agents and/or amorphous polymers as plasticizers. P(3HB--3HV)-based films containing 3, 18, and 28 mol % 3HV were processed into films by extrusion and subsequent molding. The characterization results confirmed that increasing the 3HV content from 3 to 28 mol % resulted in a decrease in the melting point (from 175 to 100 °C) and an improvement in mechanical properties (i.e., elongation at break from 7 ± 1% to 120 ± 3%). The behavior of P(3HB--3HV) in the presence of additives was also investigated. It was shown that an increase in the 3HV content leads to better miscibility with amorphous polymers.