Crosslinked HDPE components

Dr. Wroblewski starting in 1986 (1996). After an initial bedding-in period, these crosslinked HDPE components have been found to exhibit very low clinical wear rates. 

Heat-resistant [218] soft foams were prepared from the blends of hdPE with E-P random copolymers. The azodicarbanamide acts as a thermal antioxidant and the crosslinking of the blend was increased by electron beam radiations and foamed at 225 °C with 2320% expansion. A blend of 35 wt.% PE-PP (8 92), 15 wt.% E-P block copolymers, and 50 wt.% EPDM showed accelerated weathering resitance [219] 1000 h probably due to crosslinking between constituents of the block copolymer, polyblend and EPDM. The effect of filler and thermodynamic compatibility on kaolin-filled PE-PP blend was studied by Lipatov and coworkers [220]. The thermodynamic interaction parameter (%) decreased and thermodynamic stability increased by filler addition, the degree of crystallinity decreased with increasing thermodynamic compatibility of the components due to sharp decrease in the phase separation rate during cooling. 

The difference with sulfur vulcanized blends was almost 26%, 25% and 22.9% of the blends still remaining, with respect to 0%, 10% and 30% TPS content. A similar finding was observed in the HVA-2 system, where 18.4%, 22% and 31.1% of the blends still remained undissolved in xylene. Since all the unvulcanized samples were being dissolved, this study proposed that the suitable time for extraction of sulfur and HVA-2 vulcanized HDPE/NR/TPS was around 8 h. Furthermore, as can be seen at 30% TPS content, the gel content of HVA-2 vulcanized blends was observed to be higher than the NR component. This could be due to the vulcanizing fraction, which may hinder complete leaching of the TPS particles. The results obtained can be explained by the fact that a stable crosslink structure had been formed after the blends were subjected to HVA-2 crosslinker. The formation of a crosslink structure implies that the blends were resistant to chemical penetration and cannot be easily removed. 

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