Effect of Alkaline Treatment and Pre-impregnation on Mechanical and Water Absorbtion Properties of Pine Wood Flour Containing Poly (Lactic Acid) Based Green-Composites

The effect of surface treatments and wood flour (WF) ratio on the mechanical, morphological and water absorption properties of poly (lactic acid) (PLA) based green-composites were studied. WF/PLA interfacial adhesion was promoted by means of alkaline treatment and pre-impregnation with dilute solution of matrix material. The composite materials were manufactured with twin screw extruder and injection molded samples were used for characterization. According to tensile test results, the inclusion of WF without any surface treatment caused high reduction at tensile strength in spite of incremental increase of modulus values. As the amount of alkaline treated WF increased, both modulus and tensile strength increased. Both alkaline treatment and pre-impregnation further increased the mechanical properties including tensile strength, tensile modulus and impact strength. Scanning electron microscopy (SEM) micrographs supported these findings. According to dynamic mechanical analysis (DMA) test results, the glass transition temperature of PLA increased with the addition of WF and the highest increment was obtained when pre-impregnated WF was used. Although alkaline treatment had no effect on water up-take properties of composites, pre-impregnation reduced the water uptake of the composite.