Bioplastic PHA puts new muscle in flexible PVC compounds

New research from Metabolix is putting an interesting twist on the fitness-of-PVC-for-medical applications debate.

Naturally produced plastics called polyhydroxyalkanoates (PHAs) can be used as a modifier to significantly improve the physical properties of a PVC compound while simultaneously reducing the amount of phthalate plasticizers needed to make the material flexible for applications such as bags and tubing.

In a presentation at the recent ANTEC, Yelena Kann, a senior polymer scientist at Metabolix said: "In addition to producing flexibility, practically every other property of PVC is changed by the introduction of plasticizers. The impact strength and tensile toughness are usually lost with plasticization."

Kann said that PHA copolymers with 25-40% rubber segments are miscible with PVC and could provide required toughness modification without a need to tightly control processing conditions required to disperse core-shell impact modifiers. The blends also demonstrate higher flexibility due to simultaneous plasticization.

"Metabolix's research has shown that PHA polymeric modifiers can be used to modify PVC to improve impact resistance and simultaneously impart some plasticization," Bob Engle, VP business and commercial development at Metabolix, told Plastics today in a follow-up interview.

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