Preparation And Properties Of Poly (Lactic Acid)/MMT Nano-composites

Polylactic acid (PLA) is a kind of polymer materials synthesised from lactic acid which fermented with renewable resources such as corn, it can be completely decomposition into water and carbon dioxide with the condition of water,becteria,acid and alkali after abandoned. PLA is believed to be the most promising biodegradable polymer materials because of biodegradable, biocompatibility and good workability. The product of polylactic acid that act as current polymer was little because the stress, brittleness, heat-resistant properties of polylactic acid limited the field of application, it will improve the properties through nanometer material modification and irradiation modification. Major achievements list as follows:1. PLA/MMT nano-composites were prepared through melt intercalation in twin-screw extruder. The microstructures, morphology of PLA/MMT nano-composites were characterized by XRD and TEM. Results showed that polylactide molecular chains insert into montmorillonite slice layers and montmorillonite dispersed in matrix with nano size. Mechanical test showed that adding montmorillonite can effectively improved the tensile strength and toughness of PLA. Vicat softening point was significantly imporved as montmorillonite joined into PLA, differential scanning calorimeter (DSC), Wide-angle X-ray diffraction (WXRD) indicated crystalline degree increased and crystalline temperature, crystalline time, crystalline size all decreased of polylactic acid when nanometer montmorillonite was filled in.2. The masterbatch is not suitable for preparation of PLA/MMT nano-composites, GPC tests showed that with the increasing number of processing, the molecular of PLA decreases which reduce the mechnical properties of materials. Annealing treatment can improve tensile strength of PLA/MMT nano-composites, however, toughness was decreased, DSC analysis indicated that the crystallinity of PLA/MMT nano-composites was improved and WXRD analysis showed that the average grain size increased after annealing treatment.3. Radiation crosslinking modification studies showed that cross-linked PLA/MMT nano-composites was successful prepared by joining three allylic urea different acid ester (TAIC) after radiation. The results showed that crosslinking could effectively improve the tensile strength of the composites, DSC and vicat softening point test showed that radiation crosslinking can improve the thermal stability, Tm and vicat softening temperature of PLA/MMT nano-composites.