DETERMINING FRACTURE TOUGHNESS OF WOOD FLOUR/HEMP-REINFORCED PVC POLYMER COMPOSITES
Free (open access)
109 - 115
KRISZTINA ROMÁN, BELLA UDVARDI, EMESE KUROVICS, TAMÁS J. SZABÓ, KÁLMÁN MAROSSY
Rigid PVC wood flour composites were prepared with various volume fractions of wood flour to investigate the effect of the structure properties on the fractural and tensile behavior. During the mixture preparation the first question is the compatibility of the wood flour additive with the rigid PVC and the safe concentration range of the additive. The second question is the fractural behavior of the composites. Accordingly, the 300–400 micrometer particle size beech wood content was varied using 15, 20, 25 parts per weight of the polymer matrix. Since both the PVC and the major components of the beech wood (cellulose and lignin) are polar, we did not use a coupling agent between the polymer and the natural filler. Thus, the properties of the composites as function of concentration can be examined. The usual mechanical properties, such as tensile strength, elongation at break and so-called compact tensile fracture mechanical analysis was also performed. It has been found that the composites could be safely processed with up to 25 parts by weight wood content. However, the properties of 25 parts by weight filler content sample already showed a decrease in strength properties. We also tried to improve the fracture mechanical properties with fibrous (1 cm long) natural filler. In this case 20 parts by weight of wood flour content with one, three and five parts by weight hemp fiber were used in the PVC polymer matrix. The tests results showed that these fibrous fillers neither decrease nor improve the mechanical properties. The raw measurement results were evaluated according to the critical stress intensity factor (Kc) and the critical crack propagation energy (Gc). Ultrasound propagation measurements are in progress trying to determine the effect of structural changes and interactions at increased hemp fiber content.
PVC composite, mechanical properties, Kc, Gc, LEFM