Preparation and properties of metallocene linear low density polyethylene/natural rubber/epoxidised natural rubber composites
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Date
2014
Authors
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Publisher
Universiti Teknologi Malaysia
Abstract
Polyethylene has been used as insulation materials in wire and cable applications due to its excellent non-conductive electrical properties. The effect of (90/10) natural rubber/epoxidised natural rubber blend ratio, organo-montmorillonite (OMMT), magnesium oxide (MgO), zinc borate (ZB) with the presence of 2 parts per hundred (phr) N,N-m-phenylenebismaleimide (HVA-2) cross linking agent on the mechanical, dielectric, thermal, flammability, morphology and crystallinity properties of metallocene linear low density polyethylene (mLLDPE) blends were investigated. Blends were prepared by melt mixing in a twin screw extruder, remixing in milling machine and compression molding. The results from the field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infra-red spectroscopy (FTIR), limiting oxygen index (LOI), differential scanning calorimetry, thermogravimetry, tensile strength, elongation, modulus, dielectric constant and loss, breakdown and volume resistivity tests were discussed. The 90/10 mLLDPE/(NR/ENR) blend showed the highest tensile strength values. The results also showed that with increasing rubber loading, the dielectric properties of mLLDPE continuously decreased while the volume resistivity continuously increased. The blend was compounded with different OMMT, MgO and ZB loadings for further studies. The results showed that the tensile strength and elongation at break decreased, while tensile modulus increased with increasing MgO, ZB and OMMT loadings. Also the permittivity increased with increasing voltage in the range of voltage 1-5 KV in all blends. FTIR showed that the epoxy and double bond groups were found to be absent in blends. The loading of 15 and 20 phr MgO in the blends improved the dielectric properties. The thermal stability and LOI were improved with increasing MgO, ZB and OMMT loadings. The overall results showed that optimum blend ratio for cable insulation applications were observed to be at 90/10 mLLDPE/ rubbers, 20 phr MgO, 6 phr ZB and 4 phr OMMT which has a good balance in terms of mechanical, dielectric and flame resistance properties.
Description
Thesis (PhD. (Polymer Engineering))
Keywords
Insulation (Heat), Metallocenes, Dielectrics—Research, Materials—Mechanical properties