Preparation And Properties Of PLA/POE/Nano-SiO₂ Composite

Polylactide (PLA) is produced from renewable resources, such as cornstarch, and is one of most important and promising bio-based and biodegradable material. It has the similar performance of polystyrene and can be processed by common plastics processing equipments, such as extrusion, injection, stretching, spinning and blow molding. PLA has tremendous market potentials in packing materials, fibers, agricultural films and biomaterials. However, some of its properties such as toughness are not satisfactory for various end-used applications and its brittleness must be improved.The novel polyolefin thermoplastic elastomer---ethylene-octene elastomer (POE) was used to modify the brittleness of PLA. In an attempt to balance the overall properties, nano-SiO2 was used as the reinforcing agent and PLA/POE/nano-SiO2 composites were prepared.Ethylene-glycidyl methacrylate copolymer (EGMA) was used as a compatibilizer for PLA/POE blends. The results showed that the hydroxyl or carboxyl of PLA can react with the epoxy of EGMA and the formed grafted polymer improved the compatibility between the interface of PLA and POE. SEM was used to analyze the dispersion of POE in PLA, and it was found that PLA/POE blends showed the "sea-island" structure. EGMA could effectively reduce the particle size of POE. When the content of EGMA was 2wt%, the particle size of POE reached to a minimum and POE particles distributed in PLA evenly. When the EGMA content was 2wt%, the elongation at break of PLA/POE (80/20) blend reached to 107% and the impact strength of PLA/POE blends increased with EGMA content. At the same EGMA content (2wt%) the particle size of POE increased with the POE content. In order to balance the tensile strength and toughnes of PLA/POE blends, the best weight ratio of PLA to POE was 90 to 10.In attempt to balance the overall properties, nano-SiO2 was used as the reinforcing agent and PLA/POE/nano-SiO2 composites were prepared by twin screw extrusion and its structure and properties were studied. SEM results showed that the section of PLA/POE blends became rougher after adding nano-SiO2 and the interface between PLA and POE was fuzzy. Small amount of nano-SiO2 could reduce the particle size of POE. Thermal analysis results showed that there was no influence of POE and SiO2 on the glass transition temperature and melting point of PLA. Nano-SiO2 could act as a nucleating agent for PLA and promoted the crystallization of PLA. SiO2 limited the chain movement of PLA and resulted in the increase of the storage modulus, loss modulus and viscosity of PLA/POE/nano-SiO2 composites. The Young's modulus of PLA/POE/nano-SiO2 composites increased with the increase of nano-SiO2 content. Both the tensile strength and elongation at break reached a maximum when the nano-SiO2 content was 0.5wt%, and decreased with the continued increase of SiO2 content.