A novel approach to the impact modification of PLA

Abstract

The concept of adding synthetic polymer fibers for the impact modification of poly(lactic acid) (PLA) was investigated in this study. Poly(ethylene terephthalate) (PET) and poly(vinyl alcohol) (PVA) fibers were used as impact modifiers, while wood flour as reference. Polymer fibers increase stiffness moderately but fracture resistance considerably. Impact modification remains effective even at −20 °C that cannot be achieved by traditional approaches. Local processes and fiber content are the main factors in determining the improvement in impact resistance. The mechanism of the dominating local process depends on fiber characteristics and interfacial adhesion. Different local processes influence dissimilarly the two steps of fracture, crack initiation and propagation. The absolute value of impact resistance is determined by the total energy consumption of local processes. PVA fibers are the best impact modifiers among the reinforcements studied. Plastic deformation initiated by debonding and fiber fracture consumes considerable energy. The 5 GPa stiffness and 15 kJ/m2 impact resistance of PLA/PVA fiber composites is useful for structural applications and have not been achieved before.