Preparation And Properties Of PLA/BC Composites

Polylactic acid (PLA) was given serious attention for its excellent biocompatibility and higher mechanical properties as biodegradable materials. But PLA is more sensitive to notched impact and its slow crystallization rate gives rise to amorphous structure appear in the real production process, reduced its thermostability and mechanical properties significantly. Bacterial cellulose (BC) is natural nano-materials, with larger length to diameter ratio, higher crystallinity and modulus, and a finer web-like network. BC also has favorable biodegradability, PLA/BC composite is expected to get excellent comprehensive properties as completely biodegradable composites. However, BC has strong hydrophily and worse compatibility with hydrophobic polymer materials, such as PLA. So it become the researched hot spot to improve composite material compatibility and find a suitable blending method. PLA and BC were selected as matrix and reinforcement respectively to prepare PLA/BC biological composites with interpenetrating networks structure via blending diffusion of PLA-chloroform solution and BC-anhydrous ethanol dispersion.The micro-morphology, dispersibility, mechanical properties, spherulite morphology, isothermal and non-isothermal crystallization kinetics, melting behavior, and thermal decomposition property of the composites were investigated by scanning electron microscope (SEM), polarized optical microscopy (POM), differential scanning calorimetry (DSC) and thermogravimetry analysis (TGA). The results show that the blending diffusion method was available for the preparation of PLA/BC composites with interpenetrating networks structure of PLA wound on the surface of BC skeleton.BC can improve the mechanical properties, adding an appropriate amount of BC, the tensile strength, elongation at break, bending strength, bending modulus and notched impact strength of PLA/BC composites are improved, and all mechanical properties was a maximum performance in BC content is 1.0%.As a heterogeneous nucleating agent, proper amount BC can improve the crystallization rate, crystallinity and the thermal decomposition temperature of PLA/BC composites, refine the spherulite simultaneously, the 1.0%BC content is the best value for PLA/BC composites.The non-isothermal crystallization of PLA/BC composites, the crystallization temperature, melting temperature and crystallinity of PLA/BC composites decreased with the increasing of cooling rate. MO’s theoretical model can describe the non-isothermal crystallization kinetics of PLA/BC composites very well. The isothermal crystallization of PLA/BC composites, the crystallization time increased with the rising of crystallization temperature, Avrami’s equation can describe the isothermal crystallization kinetics of PLA/BC composites very well.