The Mechanical and Thermal Properties of Poly(ethylene--vinyl acetate) (PECoVA) Composites with Pristine Dolomite and Organophilic Microcrystalline Dolomite (OMCD).

Poly(ethylene-co-vinyl acetate) (PECoVA) composite containing organophilic microcrystalline dolomite (OMCD) was studied to replace the non-recyclable silicone elastomer in biomedical application. Pristine dolomite (DOL) is an inorganic mineral filler and is hydrophilic in nature, hence incompatible with most polymers and limits its use in biomedical applications. DOL was subjected to a combination of size reduction, tip sonication and a surface modification process to obtain a more effective dolomite filler, known as OMCD, as reinforcement material in the PECoVA copolymer matrix. The effects of DOL and OMCD loadings (1, 3, 5 wt%) on the structure and properties of the PECoVA composite were investigated. According to the X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), tensile and tear tests, dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) analysis, the use of the OMCD filler brought a more pronounced positive impact to the PECoVA matrix as opposed to the DOL, where it enhanced the crystallinity of the matrix and led to much better matrix-filler interfacial interactions. Therefore, regardless of the filler loading, the PECoVA/OMCD composites demonstrate greater mechanical and thermal properties compared to the PECoVA/DOL composites. The best composite was produced with the OMCD loading of 3 wt%, in which the tensile strength (22.1 MPa), elongation at break (1413%) and Young's modulus (2.0 MPa) of the copolymer matrix were increased by 44%, 23% and 21%, respectively. This proved that the combination of size reduction, tip sonication and the surface modification technique is efficient to obtain the PECoVA/dolomite composite with improved performance.