Effects of Accelerated Freeze—Thaw Cycling on Physical and Mechanical Properties of Wood Flour/PVC Composites

Abstract

Various formulations of wood flour and rigid polyvinyl chloride (PVC) composites were prepared and the effects of three accelerated freeze—thaw cycles on their physical and mechanical properties were studied according to ASTM D7031 specification. Beech (Fagus orientalis) wood flour, PVC, maleic anhydride polyethylene (MAPE), and beech veneer were used to produce the composites in a two-step conventional hot press system. A thickness swelling test was carried out as an indicator of physical property. Mechanical characteristics of composites were evaluated after each cycle using three-point flexural tests, and losses in mechanical properties were studied. Results indicated that thickness swelling was not affected by freeze—thaw cycling while significant relationship was observed between PVC content and thickness swelling and with increase in PVC content, maximum thickness swelling decreased. The values of flexural strength (MOR) and modulus (MOE), were significantly affected by PVC content, layer, and freeze—thaw cycling. Layering of the specimens and higher PVC contents improved MOR and MOE while freeze—thaw cycling decreased them at the first cycle. Repeated freeze—thaw cycling did not exhibit a significant effect on the mechanical properties and the effect of the cycles was confined to the first cycle only. Increase of PVC content had positive effect on both physical and mechanical properties.