On the use of ball milling to develop PHBV-graphene nanocomposites (I)-Morphology, thermal properties, and thermal stability

In the first part of this work, novel nanocomposites based on poly (3-hydroxybutyrate co-3-hydroxyvalerate) (PHBV) and functionalized graphene nanosheets (FGS) were prepared through ball milling. As revealed by morphological characterization, this blending methodology was able to allow proper nanofiller dispersion and distribution into the matrix. Thermal properties were studied under non-isothermal and isothermal conditions and the addition of FGS into PHBV matrix, although no changes in crystallization mechanism were observed, it modified the crystallization kinetics leading to increased crystallinity. Thermal stability analysis revealed that FGS affected the mechanism of oxidative thermal degradation and had no effect on thermal degradation by pyrolysis. Furthermore, an analysis of isothermal degradation kinetics showed that FGS speeded up the degradation rate. The Sestak-Berggren model was used as a model to explain the isothermal degradation behavior of the obtained materials in good agreement with the experimental data. ; J. Ambrosio-Martín thank the Spanish Ministry of Economy and Competitiveness for the FPI grant BES-2010-038203. M.J. Fabra is recipient of a “Juan de la Cierva” contract from the Spanish Ministry of Economy and Competitiveness. The authors acknowledge financial support from the MINECO (MAT2012-38947-C02-01 project) and from the FP7 ECOBIOCAP project.