Study On Blending Modification Of P(3HBb-co-4HB)/PLA

Poly(3-hydroxybutyrate-co-4-hydroxybutyrate)[P(3HB-co-4HB)] is a kind of thermo-plastic aliphatic polyester which is synthesized by microbial fermentation. Owning to many advantages such as biodegradability and biocompatibility. it has a well applicable prospect. However, its application is limited to a certain extent because it is expensive, quite brittle and has poor thermal stability. In this paper, PLA was used to blend with P(3HB-co-4HB). Melt chain extending and melt grafting were used to prepared P(3HB-co-4HB)/PLA blends respectively. The effects of several additives on the crystal properties, fracture morphologies, rheological properties, processing performance and mechanical properties of the blends were studied via differential scanning calorimeter (DSC), scanning electron microscope (SEM), capillary rheometer, HAAKE and electronic universal testing machine, etc.The results show that the compatibility of the two phases and apparent viscosity of blends were obviously improved by chain extenders. The optimal effect of modification were obtained at1.5phr IPDI and1.Ophr TPP, at which the breaking elongation and impact strength of blends were34.5%/69.6%and89.6%/81.0%respectively. The tensile strength of blends increased by8.3%at1.5phr IPDI and decreased slightly with TPP. It means that the effect of chain extension with IPDI was superior to that of TPP. Comparing different process, one step method was superior to two step method. As the stabilizer, antioxidants effectively improved the thermal stability of blends modified with TPP.The graft ratio and mechanical properties of composites were first increased and then decreased with increasing MAH and BPO ratio for melt grafting. The compatibility, tensile strength, flexural strength and impact strength of blends were significantly improved at MAH and BPO was1.0phr and0.3phr respectively. Due to the mutual interaction was reinforced via introducing polar group onto molecular structure, the interfacial strength and compatibility of two phases were improved. Addition of the lubricant increased fluidity of blends, improved dispersion of two phases, shorten plasticizing time, reduced apparent viscosity and plasticizing torque.