We prepared silane cured PP/metallocene polyethylene to form a thermoplastic vulcanizate. Metallocene polyethylenes (mPE) with two different levels of comonomer contents were grafted with various amounts of vinyltriethoxy silane. Thermal behaviors remained largely unchanged for PP, indicating a dominant effect of cured mPE domains on mechanical properties for the vulcanizates. Tensile strength decreased with increasing the levels of silane concentrations but leveled off at higher silane concentrations at all test temperatures. Tear strength generally decreased with reduced energy dissipation at higher degrees of cure. By relating tensile strength to tear strength, the corrected depth of flaw was ca. 85 +/- 8 mu m which was about twice higher than the natural flaw size of 40 +/- 20 mu m obtained from several different approaches for conventional elastomer, but comparable for other types of thermoplastic vulcanizates. The application of Rivlin and Thomas's theory for this newly developed TPV should be cautious due to its limitation. A further modification of previous theory for thermoplastic elastomers is necessary. The crack tip diameter (effective diameters of fracture zones) deduced from intrinsic energy density and tear strength gave a similar order in comparison with several materials.
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JOURNAL OF POLYMER ENGINEERING Volume: 28 Issue: 4 Pages: 203-223
