Improvement of thermal properties of polyhydroxybutyrate by grafted chemicals

Abstract

The crystallization and thermal degradation behaviors of polyhydroxybutyrate (PHB) grafted with maleic acid (MAc) and exo-3,6-epoxy-1,2,3,6-tetrahydrophthalic anhydride (ETA) are analyzed with differential scanning calorimetry (DSC), dynamic thermogravimetric analysis (TGA), and gel permeation chromatography (GPC). It is obtained that the PHB grafted with MAc or ETA has a faster crystallization rate, larger crystallinity, and better thermal stability than the as-received PHB. The thermal stability of specimens are in the order of the as-received PHB < PHB grafted with ETA < PHB grafted with MAc. The grafting ratio of MAc is larger than that of ETA. The thermal stability of PHB can be greatly improved by grafting a small amount of MAc. The activation energy of the PHB degradation reaction are little affected by the grafted chemicals, nonetheless, the reaction order and frequency factor are significantly affected by the grafted MAc.