Glass fiber reinforced PLA composite with enhanced mechanical properties, thermal behavior, and foaming ability

Polylatic acid (PLA) and PLA foams show a promising prospect for replacing the traditional petroleum-based polymers and foams. However, PLA shows poor ductility, thermal stability and foaming ability, and its application is significantly limited. Herein, silane-modified glass fibers (m-GF) were adopted to improve the mechanical properties, thermal stability, and foaming ability of PLA. PLA/m-GF composites with different GF contents were firstly prepared by twin-screw compounding. Microscopic morphology analysis showed that silane-modified GF has a good bonding with PLA matrix, and increasing GF content led to slight decreased of GF length. Mechanical testing showed that GF led to simultaneously enhanced strength, rigidness, and toughness. The higher the GF content is, the more obvious the reinforcement effect is. With 20 wt% GF, the PLA/m-GF composite shows almost 2-fold enhanced strength and rigidness, and more than 3-fold enhanced impact toughness than the pure PLA. The outstanding mechanical properties arises from the strengthening effect of the GF network skeleton that shows good bonding with PLA matrix. Thermal analysis showed that GF led to increased heat deflection temperature but reduced melt flow index of PLA. Foaming experiments showed that GF can dramatically improve the foaming ability by increasing expansion ratio and refining cellular morphology. Microcellular PLA/m-GF foam with an expansion ratio of up to 20-fold and cell sizes less than 10 mu m was achieved. Thus, the strong PLA/m-GF composites and their foams show a promising future in preparing lightweight structural components used in many applications such as automotive and aircraft industries.