FLEXURAL FATIGUE BEHAVIOUR OF NEW ENGINEERED BIOCOMPOSITES FROM POLY (3-HYDROXYBUTYRATE-COHYDROXYVALERATE) (PHBV)/POLY (BUTYLENE ADIPATECO-TEREPHTHALATE) (PBAT) BLENDS AND SWITCHGRASS

摘要

Recently, environment friendly biodegradable composites made of biopolymer matrix reinforced with natural fibres have been developed in order to compete with conventional composites. Pre-blend of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/poly (butylene adipate-co-terephthalate) (PBAT) incorporated of switchgrass were successfully produced by injection molding as new biocomposites [1]. It was shown that the addition of compatilizer, poly diphenylmethane diisocyanate (pMDI) improved the tensile properties and heat deflection temperature of the compatibilized biocomposite compared to the virgin composites of PHBV/PBAT/switchgrass [1]. The mechanical damage caused by cyclic loads in fatigue loading results in a material failure at stress levels that are lower than the static strength. For this reason, in this study, flexural fatigue behavior of two switchgrass based biocomposites was investigated using the four point bending test. The matrix material of the composite systems was a pre-blend of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/poly (butylene adipate-co-terephthalate) (PBAT). PHBV-PBAT blend with (i) 30 wt% switchgrass; (ii) 30 wt% switchgrass and 0.75 parts by weight compatibilizer, poly diphenylmethane diisocyanate (pMDI), were selected for this investigation. Furthermore, the fracture surfaces of tested specimens were also examined since it has been shown that SEM micrograph observation could be useful to study the failure mechanisms of composites under flexural fatigue loading [2].