Preparation And Characterization Of Poly(Lactic Acid)/Esterified Cellulose Composites

The study on the development and application of the environment-friendly bio-degradable polymer has attracted increasing attention with the aggravation of energy shortage and "white pollution" more and more countries will carry out the basic national policy on the sustainable development and resource recycling society. Polylactic acid (PLA), coming from many renewable resources (such as starch), has become one of the most important materials due to its good biodegradability and biocompatibility. However, PLA has some shortages, for example, the crisp texture and the low softening point. In order to make better use of PLA, it must be modified by means of copolymerization and blending it with other materials. Among the PLA-base blending system, the material of cellulose that is naturally degradable and regenerated has been receiving much concern. Unfortunately, cellulose dispersed badly in the composites and the interfacial adhesion between cellulose and PLA is poor.In this paper, cellulose was esterified by maleic anhydride (MA) in a gas-solid reaction system, The conditions for esterification were optimized and the properties of esterified cellulose were characterized. The esterification reaction was carried out in a hydrothermal reactor, which can avoid the use of large amounts of organic solvents. PLA/esterified cellulose composites were prepared by melt blending technology and the properties of the composites were investigated in detail. Though esterified cellulose dispersed fully in the composites, the interfacial adhesion between esterified cellulose and PLA was weak, which leaded to unsatisfactory properties of the PLA/esterified cellulose composites.When adding the initiator into the composite system, the properties of the PLA/esterified cellulose composites were enhanced. on the one hand, the initiator can induce the cross-linking reaction between esterified cellulose and PLA, on the other hand, the initiator can increase the viscosity of the system and enhance the physical winding between esterified cellulose and PLA.When CaCO3 added to the PLA/esterified cellulose composites, some interaction between esterified cellulose and CaCO3 was existed that was proved through mechanical properties testing, TGA, GPC, and FTIR. This interaction improves the mechanical properties and thermal stability of the composites to a certain extent, and is helpful to slow down the thermal degradation of PLA.Based on the study on the interaction between esterified cellulose and CaCO3, the esterified cellulose combined with nano-CaCO3 was as a compound filler, and PLA/esterified cellulose/nano-CaCO3 composites were prepared. When the filler content is less than 5%, the mechanical properties of the composites is improved obviously compared with pure PLA, Whereas, when the filler content is more than 5% in the composite, the mechanical properties decreased with the increase of filler. The properties of isothermal and non-isothermal crystallization of the composites were studied in this paper, and the results indicate that the filler acts as a nucleating agent in PLA. The SEM obviously showed that the esterified cellulose could be well dispersed in PLA, but the nano-CaCO3 with high content obviously gather together, and then lead to unsatisfactory properties of the composites.