HIGH ELONGATION FKM FORMULATIONS WITH IMPROVED MOLDING PROPERTIES

摘要

It has been found that certain peroxide/coagent crosslinked blends of a peroxide- crosslinkable FKM fluoroelastomer with a similar non-peroxide crosslinkable FKM fluoroelastomer exhibit increased elongation to rupture, improved demoldability, and slightly reduced durometer compared to prior art peroxide-cured FKMs. The degree to which these desirable changes are realized is greatest when the monomer ratios of the peroxide-crosslinkable FKM fluoroelastomer are similar to the monomer ratios of the non-peroxide crosslinkable FKM. The improved demoldability of these compositions is believed to be due to improved hot tear strength and especially increased elongation at molding temperature; these properties are important in the process of removing complex parts from a mold after forming, whether by compression, transfer, or injection molding. Hot tear strength and elongation are especially important in removal of FKM molded parts with 'undercuts' in the mold. In particular, these blends exhibit better demoldability than similar purely peroxide-crosslinked FKM compounds, without being sticky. These compositions are also useful without post cure (as are standard peroxide-cured FKMs, especially those with iodine cure sites).