DETERMINATION OF STRAW PARTICLE SIZE EFFECT ON THE WATER ABSORPTION OF STRAW-PLASTIC COMPOSITES

The main aim of this paper is to present the research findings which come out from the experimental determination of the influence of input raw material properties and composition on the water absorption of straw-plastic composites (SPC). During the SPCs production, important raw material parameters such as straw sawdust particle size, straw/plastic concentration ratio or type of plastic matrix can be recognized. In this research study, the aim was to produce SPCs of an acceptable and competitive level of quality which is determined from the final mechanical properties of SPCs. Particle size of straw sawdust used for production of SPC has significant influence on mechanical properties of composites and also on other important properties (water absorption, hardness, frost resistance, etc.). The paper deals with the determination of the impact and the relationship between the input straw sawdust particles sizes, straw/plastic concentration ratio and water absorption of composites. By side intention of authors is to determine the possibilities of waste raw materials usage. The experimental research findings were obtained using a semi-operational injection molding press where the injection is provided by a working screw. As the input raw material, wheat straw, HDPE plastic matrix and recycled HDPE, represented by lids from PET bottles, was used. The effect of the input straw sawdust particle size on water absorption was determined according to a combination and default levels of straw/HDPE concentration ratio, using recycled HDPE instead of virgin HDPE and particle size of straw sawdust.