Mechanical and rheological properties of wood plastic composites based on polypropylene and birch plywood sanding dust

Article summarizes investigation results of thermal, mechanical and rheological properties of industrially prepared two new wood plastic composites, based on a virgin polypropylene (PP) and birch plywood production residues-plywood sanding dust (PSD). The studies revealed that the tensile strength of composites increased about 25-30% and the modulus for 4.0-4.5 times, but the lightness, the whiteness degree and the common colour changes are smaller in comparison with previously investigated similar composites [5,6].The softening temperatures by VIKA of approbated composites are 154.4 and 158.6°C. The starting temperatures of thermal oxidation are 250.5 and 253.5°C and the thermal expansion of samples at 90°C is only 3%. The rheological experiments showed the decrease of composite melts viscosity with the increase of temperature and the shear rate, but the fluidity index is smaller than 1, that is typical phenomenon for pseudoplastic polymer liquids. The SEM pictures of the fractured surface replicas confirmed that the composites failure has mixed character: partially fracture the polymer matrix and the border surface of polymer matrix and wood fibre.