Studies on confined crystallization behavior of nanobiocomposites consisting of acetylated bacterial cellulose and poly (lactic acid)

This article deals with the confined crystallization behavior of nanobiocomposites consisting of acetylated bacterial cellulose (BC) and poly(lactic acid) (PLA). PLA/acetylated BC nanobiocomposites were prepared by compressed molding. Nonisothermal crystallization, melting behavior and isothermal crystallization kinetics within confined spaces were investigated by differential scanning calorimetry (DSC). The results indicated that acetylated BC was favorable to the crystallization of PLA at higher temperatures. On one hand, due to better compatibility between acetylated BC and PLA, crystal nucleation and growth of PLA took place while crystallization process of PLA was restricted. Acetylated BC had an effect of heterogeneous nucleation on PLA crystallization. On the other hand, crystal growth of PLA molecular chain was confined within the nanometer gaps between the microfibrils of acetylated BC. The interaction between microfibrils of acetylated BC and PLA also had an effect on the crystal growth of PLA, which resulted in the growth of confined crystallization. As the time course of acetylation became longer and longer, the compatibility of acetylated BC and PLA was enhanced and the crystallization of PLA became more difficult. This result was in accordance with the observation of polarized optical microscope (POM) pictures. Activation energy of crystallization and free energy surface of PLA were reduced in PLA and acetylated BC composites.