Mechanical properties and thermal stability of modified calcium sulfate whisker-reinforced polydimethylsiloxane/ethylene-vinyl acetate copolymer composites

Polymeric composites of polydimethylsiloxane (PDMS) and ethylene-vinyl acetate copolymer (EVA) with unmodified and modified calcium sulfate whisker (CW and mCW), were prepared through melt compounding method. The surface of CW was modified with 3-aminopropyltriethoxysilane (KH550), 3-glycidoxypropyltriethoxysilane (KH560), and 3-methacryloxypropyltriethoxysilane (KH570) by a dry process to increase its dispersion into the PDMS/EVA matrix and the compatibility between PDMS and EVA. The surface modification of CW was confirmed by energy dispersive spectroscopy (EDS). Fourier transform infrared spectroscopy (FTIR) was used to confirm the presence of various functionalities of the CW/PDMS/EVA and mCW/PDMS/EVA composites. The mechanical properties, thermal stability, morphology, and hydrophobicity of the composites were investigated. The thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to characterize the thermal performance of the composites. The results showed that the thermal stability of all resultant composites, loaded with CW, is better than those of PDMS/EVA blends. Furthermore, the tensile strength of KH560-CW/PDMS/EVA increased to 66% compared to CW/PDMS/EVA composites at 20 phr of KH560-CW. In contrast, the tensile strength of KH550-CW/PDMS/EVA and KH570-CW/PDMS/EVA composites with 5 phr of KH550-CW and KH570-CW improved as compared with CW/PDMS/EVA composite, respectively. The contact angle and electrical properties of CW/PDMS/EVA and mCW/PDMS/EVA composites were also measured.

Automated summary

Polymeric composites of PDMS and EVA with unmodified and modified calcium sulfate whisker were prepared via melt compounding method. The surface of CW was modified to increase its dispersion into the PDMS/EVA matrix. The thermal stability and mechanical properties of the composites were improved with the addition of modified CW. The contact angle and electrical properties of the composites were also measured.