Metabolix, Inc., Cambridge, Mass., has developed a series of biobased PHA copolymers that act as impact modifiers, flexibilizers, and processing aids for rigid and flexible PVC. PHA is a bioresin produced by microbial fermentation of plant starches. Data on the new copolymers was presented at the recent SPE Vinyltec conference in Chicago by Dr. Yelena Kann, sr. polymer scientist at Metabolix.
She said the new PHA copolymers are readily miscible with PVC and can perform as high-molecular-weight, readily dispersible flexibilizers that show low migration, low extractables, and little volatile loss or staining characteristics. Unlike standard plasticizers, they do not reduce PVC’s toughness. Rather, their main benefit is impact modification, and PHA-rubber copolymers reportedly outperform the best commercial MBS core/shell impact modifiers and do not compromise PVC transparency or UV stability.
As a processing aid, the metal-adhering properties of PHA copolymers promote hogeneous shear melting of PVC and prevent overheating and degradation. It also allows mixing at lower temperatures. Metabolix worked with compounder AlphaGary Corp., Leominster, Mass., to validate the new PHA copolymers. Metabolix plans to produce them at a 20-million-lb/yr plant being built in Spain. Samples are available. Metabolix is also working on PHA as a modifier for PLA biopolymer