Elaboration and Characterization of Bioblends Based on PVC/PLA

International audienceWith the aim to develop new biomaterials (bioblends) to be used in the field of waste elimination, this contribution focuses on the elaboration and characterization of new materials based on poly (vinyl chloride) (PVC) and poly (lactic acid) (PLA). The bioblends based on PVC/PLA were prepared by melt mixing in the absence and presence of maleic anhydride (MAH). The binary blends were first characterized in terms of thermal (glass transition temperature) and mechanical properties (tensile and micro-hardness). Their thermal stability was investigated by thermogravimetric analysis (TGA). The results showed that this pair of polymers is not miscible and exhibited lower properties than those of the separated polymers. The in situ compatibilization was then performed using MAH and dicumyl peroxide (DCP) as an initiator. The presence of MAH enhanced the processability of the bioblends by decreasing the temperature of mixing. The properties of subsequent PVC/PLA bioblends were investigated through tensile and micro-hardness testing, thermal analysis (DSC and TGA), and SEM. From the mechanical results, high level of compatibility was found when introducing MAH. The TGA studies indicated that the incorporation of PLA in PVC (matrix) increased thermal stability of the bioblend. Microscopic observations revealed uniformly dispersed PLA in the PVC matrix, confirming that phase separation has disappeared in the presence of MAH

Effect of postharvest practices on the culturable filamentous fungi and yeast microbiota associated with the pear carpoplane

Information regarding the filamentous fungi and yeast microbiota on pear surfaces is limited when compared to other fruits such as grapes and apples. The effect of commercial postharvest practices on pear fruit surface microbiota and species composition is not known, particularly in terms of the presence of postharvest pathogens and potential biocontrol microorganisms. Pear fruit were collected at harvest in the orchards of four commercial farms, after harvest at a communal pack house following chlorine drenching and after modified atmosphere storage. Microbiological analysis showed that during season one the fungal populations on pears from the four farms were significantly lower after CA storage when compared to populations of orchard pears, however during season two, the opposite trend was observed. The yeast populations were either significantly higher or similar after CA storage compared to the orchard pear counts during both seasons. Commercial drenching led to either an increase or reduction in the filamentous fungi and yeast populations, however a definite trend could not be observed. The postharvest practices decreased the number of viable morphologically different yeast and filamentous fungal species. A total of 16 yeast and 24 filamentous fungal species were isolated. A 76% dominance of Ascomycetes was observed. Known postharvest pathogens Penicilium commune and Penicillium crysogenum were present after CA storage. Potential known biocontrol organisms included Aureobasidium pullulans, Cryptococcus sp. and Sporobolomyces roseus. Knowledge generated could contribute to development of commodity-specific supply-chain management systems and biocontrol strategies based on scientific data to reduce pear fruit losses and for quality control purposes.The National Research Foundation, the Department of Science and Technology Postharvest Innovation program and the University of Pretoria.http://www.elsevier.com/locate/postharvbio2017-08-30Plant Scienc