UV-photodegradation of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHB-HHx)

The effects of ultraviolet (UV) radiation on the properties of the biodegradable polymer, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHB-HHx), were evaluated. Photodegradation was followed by changes in molecular weight, crystallinity, morphology, and thermal properties. PHB-HHx undergoes both chain scission and crosslinking reactions upon UV irradiation. The crystallinity of PHB-HHx was higher during UV-photodegradation. scanning electron microscopy (SEM) micrographs of the PHB-HHx surface before and after UV exposure show that the photodegradation occurred via bulk erosion, not surface erosion. IR spectra showed that both the crystalline and amorphous portions of PHB-HHx were photodegraded through a Norrish type I reaction.