Investigation on Crystallinity Behavior of the Polylactic Acid and Poly-3-hydroxybutyrate Bio-based Polymers in the Presence of the Pyromellitic Anhydride

Bio-based polymers have attracted significant attentions because of their renewable nature which can be a substitute of petroleum-based polymers; moreover, such polymers do not pollute the environment due to their degradable nature. In this research,the poly lactic acid (PLA) and poly-3-hydroxybutyrate (PHB) blend, as biodegradable polymers, behavior was investigated. Different ratios of PLA/PHB blend were prepared using solution casting method in the presence of the pyromellitic anhydride (PMDA) as acompatibilizer. DSC results revealed that the PMDA presence caused to separation of α-helix crystals and β-plate in two polymers resulting in phase separation via altering the crystallinity rate. PMDA can control the crystallization phenomenon which affected the crystallization rate, percentage and crystal size. Low molecular interaction was observed using the XRD results of pure and blended samples. SEM images of samples with higher content of PLA illustrated the homogeneous dispersion of PHB. Ring opening reaction of PMDA resulted in increasing the acidic number of samples which indicated the weak interaction with active group of polymers. It was observed no shit in IR peaks which indicated the incompatibility of these two polymers. Results shed light on the PMDA behavior in PLA/PHB blend which PMDA in spite of controlling the crystallinity behavior of the blend, cannot improve the compatibility and mixing.