Heat resistance of biobased materials, evaluation and effect of processing techniques and additives

Abstract

The paper describes the effect of different manipulations (addition of fiber, nanoclay, nucleating agents and chain extender, blending, annealing, use of a higher mold temperature and stereocomplexation) on the heat resistance of poly(lactic acid) (PLA) and poly(hydroxybutyrate) (PHB). Therefore, the differential scanning calorimetry profiles, the vicat softening temperatures and the degradation temperatures were measured and compared to standard PLA, PHB, and polypropylene (PP) as reference materials. Furthermore, a comparison between VST and HDT as parameters for heat resistance was made by examining the deformation during contact with hot water. Stereocomplexation and the use of a higher mold temperature seemed the best techniques to obtain PLA‐based materials with good heat resistance, while other manipulations had little to no effect on the processed biopolymer. The addition of chain extender to PLA and PHB had no effect on processed polymers, but it did improve the thermal degradation of PLA during processing. Furthermore, hot fill tests showed that higher VST values were more reliable as a heat resistant parameter than HDT values for these kinds of application. The VST values of PHB were similar to PP, suggesting that PHB also provides opportunities as a packaging material for food products that undergo a heat treatment. POLYM. ENG. SCI., 58:513–520, 2018. © 2017 Society of Plastics Engineers