Polymers are one of the most commonly used materials and their consumption is still increasing every day. Consequently, the amount of polymer waste is also increasing, which has negative impact on the environment due to very slow disintegration process. Therefore, it is essential to reduce the environmental effect of polymers by various means. One of the possible ways is the use of highly filled wood-polymer composites. In addition to lower environmental impact, the use of these composites has increased in recent years also due to their lower price, lower specific weight, lower thermal conductivity and higher tensile strength in comparison to pure polymer materials.
The environmental impact of the polymers can be further reduced by using recycled polymers as binder materials for the mentioned composites. Polymers are usually recycled by use of mechanical recycling, during which the material is first physically crushed, and then processed with different treatment methods. The most commonly used processing method is extrusion, during which the rheological, thermal and time-dependent mechanical properties of the material usually change.
The aim of this thesis was to determine the effects of different concentration of wood particles and recycled polymer binder on rheological, thermal and time-dependent mechanical properties of wood-polymer composites. Raw and recycled polypropylene were chosen as the binder materials. The rheological and time-dependent mechanical properties were measured by Rotational Rheometer, while the thermal properties were determined with Differential Scanning Calorimetry (DSC).
The results showed that both, the increasing concentration of wood particles and the recycling of the binder material, have significant effect on the rheological, thermal and time-dependent mechanical properties of highly filled wood-polymer composites. In the prepared composites the wood particles affect the mentioned properties by hindering the movement of polymer chains of polypropylene, while the recycling process results in shortening or disintegration of those chains and consequently changes the structure of the material.