Novel engineering approaches on composite materials (part I): Effect of low temperature air plasma treatment on physico-chemical properties of kaolinite/polyethylene composites

Abstract

It was found in this study that air plasma treatment of particular kaolinite has led to the change of its wettability. This was reflected in the decreased values of water contact angles of wetting. There were determined yield locus and flow function dependencies at different stress levels for virgin and different time plasma treated samples (flow index - ffc, effective angle of internal friction - phie, unconfined yield strength - sigmac). It was found that by plasma treatment the character of the flow was shifting from region of very cohesive (ffc = 2.39) to the cohesive (ffc = 3.19). For untreated samples effective angle of internal friction was decreased with increasing applied consolidation stress, while for plasma treated kaolinite it was increased. As a result of the latter powder rheological changes was a notable improvement of the fracture toughness of prepared HDPE composites as found in the whole concentration range of degree of filling under study (from 5 to 25 w.% filler concentration) and tensile strength increase found for 5 w.% virgin kaolinite filled polyethylene composites. This improvement to the fracture toughness became more marked as the filler loading increased, indicating an improved degree of filler/matrix interaction.