Thermal degradation of PHB/clay nanocomposites: effect of treatment and processing

D. A. D'AMICO; V. P. CYRAS; R. P. OLLIER; W. F. SCHROEDER; V. A. ALVAREZ

Congreso; Congreso Internacional de Metalurgia y Materiales.; 2016

Biodegradable polymers and, in particular, polyhydroxyalkanoates (PHAs) represent an interesting alternative to synthetic polymers due to many advantages related with their biodegradability and biocompatibility and also because they are produced from renewable resources. Nevertheless, they have several disadvantages related with mechanical and barrier properties. In order to overcome such disadvantages one alternative is the preparation of nanocomposites because the nanoparticles are able to enhance the material properties [1]. There are in the literature several studies focalized in PHB or PHBV/ montmorillonite (MMT) based nano-biocomposites. The main drawback is its thermal instability during melt processing. Due to the particular temperature sensitivity of PHA family, that restricts the use of melt processing [2].Kinetic data obtained from TGA are very useful for understanding thermal degradation process and also to identify whether filler helps to improve the thermal stability of material. There are several reports for the thermal degradation of of PHB-based nanocomposites reinforced by of alkyl quaternary ammonium MMT. Xie et al. [3] has pointed out the complex degradation reactions that could exist in organically modified MMT and consequently, in nanocomposite with those kind of clays.In this work, the influence of clay and clay modifiers (silane and phosphonium) on the thermal degradation of a biodegradable bacterial poly(3-hydroxybutyrate), PHB, were studied. We have analyzed combined reactions of cationic exchange, silylation and acid activation of bentonite (E-S-A-Bent) which was the best treatment of a previous work[4]. The obtained results reveal that organic modifiers greatly enhance the degradation leading to a dramatic decrease in PHB molecular weight. A kinetic analysis based on the Coats and Redfern model was applied to the non-isothermal TGA data. The results demonstrate that the surfactants effectively have a catalytic effect on the PHB degradation.