Polymer Alloys of Nodax Copolymers and Poly(lactic acid)

TLDR

Nodax consists of bacterially produced polyhydroxyalkanoate copolymers containing 3‑hydroxybutyrate and other 3‑hydroxyalkanoate units with side chains of at least three carbons. The study investigates the properties of polymer alloys made from poly(lactic acid) and Nodax copolymers. By incorporating medium‑chain‑length 3HA units, the authors lower the crystallinity and melt temperature of the PHA copolymers, and particle size further modulates crystallization rate through reduced spontaneous nucleation. Blending a small amount of ductile PHA into PLA yields a renewable polymer alloy with markedly improved toughness and optical clarity, owing to reduced crystallinity and delayed crystallization of dispersed PHA domains.

Abstract

Abstract Summary: Properties of polymer alloys comprising poly(lactic acid) and Nodax copolymers are investigated. Nodax is a family of bacterially produced polyhydroxyalkanoate (PHA) copolymers comprising 3‐hydroxybutyrate (3HB) and other 3‐hydroxyalkanoate (3HA) units with side groups greater than or equal to three carbon units. The incorporation of 3HA units with medium‐chain‐length (mcl) side groups effectively lowers the crystallinity and the melt temperature, T m , of this class of PHA copolymers, in a manner similar to that of alpha olefins controlling the properties of linear low density polyethylene. The lower T m makes the material easier to process, as the thermal decomposition temperature of PHAs is then relatively low. The reduced crystallinity provides the ductility and toughness required for many plastics applications. When a small amount of ductile PHA is blended with poly(lactic acid) (PLA), a new type of polymer alloy with much improved properties is created. The toughness of PLA is substantially increased without a reduction in the optical clarity of the blend. The synergy between the two materials, both produced from renewable resources, is attributed to the retardation of crystallization of PHA copolymers finely dispersed in a PLA matrix as discrete domains. Effect of the particle size on the overall crystallization rate by low spontaneous nucleation frequency. image Effect of the particle size on the overall crystallization rate by low spontaneous nucleation frequency.