Influence of post-fabrication annealing on PHA film properties.

摘要

Polyhydroxybutyrate (PHB), is a bacterial polyester receiving much attention as it is genuinely biodegradable, but its brittleness hampers its applicability. The present study was conducted to evaluate the effect of annealing on mechanical properties of Polyhydroxybutyrate (PHB) copolymer films. Films were made by using a Randcastle extruder fitted with a coat-hanger cast film die and then annealed at 5 different temperatures and for varying times (5 min, 30 min., 1 hr, 2 hrs). Three mil thick film samples were used for impact testing, tear testing, and tensile testing. Differential Scanning Calorimeter (DSC) and an optical refractometer were used to observe the changes in crystallinity. It appears possible to toughen PHB copolymer using an annealing treatment. The results showed a two-fold increase in dart impact and tear strength at 80 °C and at 100 °C, while a three-fold increase was observed for films annealed at 120 °C. Tensile testing results showed improvements in strain hardening with a decrease in modulus with increasing annealing temperature. Annealing appeared to induce structural reorganization. In conclusion the relaxation of the chains in the amorphous phase could be the reason for the improved properties.