Contact angle of untreated/treated kaolin and its correlation with the mechanical properties of PP-kaolin composites

This research relates the effect of contact angle and surface free energy on the mechanical properties of chemically treated and untreated kaolin filler polypropylene (PP) composites. The contact angle of untreated as well as treated kaolin filler samples was obtained using thin layer wicking technique and Washburn’s equation. The information recorded is incorporated into the Young’s equation to obtain the value of surface free energy. The interfacial adhesion of the composite was quantitatively analyzed by using the Pukanszky model. Treated and untreated kaolin filler samples were compounded with PP in a Brabender Plasticorder to produce a PP—kaolin composite. The compound consists of various filler contents ranging 0%, 5%, 10%, and 15%. Tensile, flexural, and impact tests show that treated samples have stronger mechanical properties than untreated PP—kaolin composite. The thin layer wicking technique shows that for treated kaolin samples, a high contact angle is obtained. The surface energy obtained was also low for treated kaolin samples. A conclusion could be made here that high contact angle will have lower surface energy which will then lead to an increase in compatibility of kaolin filler in the composite. Increase in compatibility will increase the mechanical property, which is portrayed by treated PP—kaolin composite samples.