Influence of photodegradation with UV radiation in biotreatment with Paecilomyces variotti on PHBV/GNS nanocomposites

Graphite nanosheets (GNSs) and poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) nanocomposites were prepared by solution casting method. This study aimed to evaluate the effects of previously phototreatment with ultraviolet (UV) radiation on the biotreatment with Paecilomyces variotti of neat PHBV and PHBV/GNS nanocomposites. Some samples of PHBV film were submitted only to biotreatment with P. variotti during 120 days; other samples were subjected to phototreatment (UV radiation) for 30h followed by biodegradation assessment with P. variotti for a period of 120 days. The effects of biotreatments on thermal properties were studied through differential scanning calorimetry. The PHBV films were monitored by weight changes as a function of time. Also, their surfaces were examined after the tests using scanning electron microscopy, contact angle and roughness measurements. The level of oxidation was recorded by means of carbonyl index evaluation by Fourier transformed infrared spectroscopy spectroscopy. The phototreatment of PHBV films influenced the process of adhesion and colonisation by P. variotti on the surface of the films, and enhanced morphological and structural changes.