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Poly(lactic acid) is at present the most promising and commercially available bio‐based and biocompostable (bio)plastic. The properties of PLA, however, are rather poor, notably its low glass transition temperature Tg of ∼55 °C, its intrinsic low crystallization rate and the limited barrier properties with respect to water, oxygen and carbon dioxide in comparison with to oil‐based counterparts, notably polyesters (PET). In this manuscript we address the question of what could ultimately be achieved in terms of barrier properties when PLA is crystallized fully. In fact, this question is rather academic in view of the long crystallization/annealing times needed to obtain maximum crystallinity but serves the purpose of better understanding current limits and notably a better understanding of the role of crystallinity on the barrier properties. A correlation is made between crystallization, various morphological parameters and the barrier properties of PLA. Crystallization of PLA causes a decrease of the oxygen permeability, but not in linear proportion with the decrease in amorphous volume. We explain this in terms of influence of the space filling and the inner crystalline structure on gas transport properties. Furthermore we suggest that the presence of a rigid amorphous fraction with lower density can have strong impact on PLA gas permeability, in particular on the gas solubility coefficient of PLA. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2247–2258, 2009

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PHB/PBS and PHBV/PBS blends are prepared via in situ compatibilization using DCP as a free‐radical grafting initiator. A considerable reduction in PBS particle size and a significant increase in the interfacial adhesion between the PHB(V) and PBS phases are observed after the compatibilization. The elongation at break of the PHBV/PBS blends was considerably increased. The local deformation mechanism indicates that matrix yielding together with dilatation, deformation, and fibrillation of the PBS particles are responsible for the improved tensile toughness of the compatibilized PHBV/PBS blends. The tensile strength, impact toughness, and elongation at break of injection‐molded PHB(homopolymer)/PBS blends are also increased after in situ compatibilization.magnified image

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