The bifunctionality of poly[(R)-3-hydroxybutyrate] in self-reinforced composite materials

The poly[(R)-3-hydroxybutyrate] (PHB) is a highly crystalline, biosourced polymer. The advantages of the PHB are its biodegradability and biocompatibility; however, the brittleness caused by its high crystallinity decreases the application ability of the PHB in comparison with the polyolefins. Excellent results were observed for the reactive extrusion of PHB in the presence of peroxides in many investigations of the modifications of PHB mechanical properties. The disadvantage must be considered to be the thermal degradation of PHB during extended extrusion and its limitation in natural composite preparation. The peroxides are highly reactive with natural fillers, and this causes a decrease of the filler's mechanical properties. Consequently, the reactive extrusion may be a useful tool for the production of additives only. The results we present of this investigation is based on a different material preparation strategy. The two-stage method incorporated additives preparation via reactive extrusion of PHB and the blending of the obtained product with neat PHB. Theself-reinforced composite material obtained in this way revealed significantly higher values of stress and strain compared to neat PHB. The thermal degradation of the PHB matrix was retarded and total crystallinity of the composite was decreased. The materials were characterized using DSC, SEM and SEC techniques. The samples were also investigated employing tensile and impact strength tests.