Abstract
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.
Highlights
This is to ensure that melt mixing process between the poly(ethylene-co-vinyl acetate) (PECoVA) and organophilic microcrystalline dolomite (OMCD) in the heated two-roll mill can be optimized without the interference of moisture that can reduce the quality of the composites
The tensile-fractured surface morphology of the virgin PECoVA, PECoVA/DOL composite and PECoVA/OMCD composite was examined through field emission scanning electron microscopy (FESEM), with the equipment model number of ZEISS LEO 1525 (ZEISS, Oberkochen, Germany) by referring ASTM F1877-98(2003)
Tensile test of the virgin PECoVA, PECoVA/DOL and PECoVA/OMCD composites was conducted by using the Universal Testing Machine Instron 5569 (Norwood, MA, USA) to determine their tensile properties according to ASTM D638
Summary
Another research study indicates the possibility to use of using dolomite as filler in enhancing the mechanical properties of the phenolic composite. Nik Adik et al reported that thermal stability of polypropylene was enhanced when reinforced with 25 wt% dolomite filler that has been treated with stearic acid [14] This proved that when the filler is chemically modified, well-blended filler and polymer matrix can be achieved and homogeneous polymer composite is formed. The dolomite which underwent size reduction through ball milling and tip sonication process, followed by surface modification using stearic acid, was employed as filler in the production of PECoVA composite. The control samples of PECoVA/dolomite composites with different loadings of pristine dolomite (DOL) were prepared and tested in order to realize the effectiveness of the size reduction and surface modification combination method in enhancing the mechanical and thermal properties of the PECoVA composite
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