Compatibilization and degradation study of Polypropylene/Poly(3-hydroxybutyrate) (PP/PHB) blends. / Estudo da compatibilização e da degradação de blendas polipropileno/poli (3-hidroxibutirato) (PP/PHB).

AUTOR(ES)
DATA DE PUBLICAÇÃO

2010

RESUMO

In this work Polypropylene/Poly(3-hydroxybutyrate) (PP/PHB) blend was studied. In particular the compatibilization and the influence of a previous photodegradation on the biodegradation of the blend were investigated. In order to understand the photodegradation of the blends it was also necessary to study the photodegradation of PHB. The compositions of the PP/PHB blends studied ranged from 90/10 to 60/40 (by weight). These blends were obtained using a twin screw extruder. The compatibilization was evaluated using a PP/PHB blend 80/20 containing or not 10% of the following compatibilizers: maleic anhydride grafted polypropylene (PP-g-MAH), poly(ethylene-co-methyl acrylate) (P(E-co-MA)), poly(ethylene-co-glycidyl methacrylate) (P(E-co-GMA)) and poly(ethylene-co-methyl acrylate-co-glycidyl methacrylate) (P(E-co-MA-co-GMA)). The blends obtained were characterized through their morphological, chemical and mechanical properties (tensile and impact tests). The results obtained enabled the classification of the compatibilizers efficiency in the following order: P(E-co-MA-co-GMA) >>P(E-co-MA) >P(E-co-GMA) PP-g-MAH. PHB photodegradability was investigated through its exposure to artificial UV radiation in a weathering chamber for 3, 6, 9 and 12 weeks. The photodegradation effect was followed by changes of molecular weight, of chemical and crystalline structures, of thermal, morphological, optical and mechanical properties, as well as of biodegradability. UV radiation caused several changes in all the properties evaluated, however, these effects were not very severe. These results could be explained in light of the low UV radiation transmittance of the PHB sample studied, which caused a strong degradation profile for this material. PP/PHB blends in all compositions were exposed to UV radiation for 2 and 4 weeks and had their biodegradability evaluated using the weight loss and the Bartha respirometer tests (CO2 production measurement). The materials before and after the different degradations were characterized by chemical, thermal, morphological and molar mass analysis. First, it was observed that, before any degradation, the biodegradation of the PHB phase was suppressed in the blends, most likely due to the fact that PHB was the dispersed phase within the mixtures studied. Previous photodegradation delayed PHB biodegradation and sped up the biodegradation of PP and all PP/PHB blends. The greater biodegradability of PP and blends was attributed to the chain scission and formation of oxidized functional groups taking place during ultraviolet radiation exposure.

ASSUNTO(S)

blendas ultraviolet radiation radiação ultravioleta blends biodegradação biodegradation

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