Biobased Rubber Modifiers for Polymer Blends

Compositions of polymer blends of polyvinylchloride (PVC) or polymethylmethacrylate (PMMA) or polyoxymethylene (POM) and polyhydroxyalkanoate (PHA) are described. In certain embodiments, the PHA is a poly-3-hydroxybutyrate-co-4-hydroxybutyrate copolymer having a weight percent 4-hydroxybutyrate of 30-45%. In other embodiments the PHA is a multiphase P3HB-4HB copolymer blend having one phase fully amorphous. The PHA is mixed with the PVC or PMMA or POM to optimize its optical, thermal and mechanical properties. In certain embodiments, the polymer is branched with optionally additives that improve properties. Methods of making the compositions of the invention are also described. The invention also includes articles, films and laminates comprising the compositions.