At present, the most common used crosslinking process for carboxylated nitrile butadiene rubber (XNBR) latex is an accelerated sulfur curing system with zinc oxide. To avoid allergenic reactions related to residual accelerator levels in dipped XNBR latex articles such as medical gloves, a dual curing process has been developed combining thermal and photochemical crosslinking reactions. The two-step procedure involves the formation of covalent and ionic bonds to ensure good mechanical properties of the final products. The photochemical thiol-ene reaction is used to generate covalent crosslinks between the remaining C¼ ¼C double bonds of the butadiene units whereas the carboxylic moieties are conventionally cured with divalent metal oxides (ZnO) under elevated temperature (formation of ionic crosslinks). The photochemical curing step is carried out both in the latex phase using a falling film photoreactor (prevulcanization) as well as in the solid phase by UV irradiation of dried XNBR films (postvulcanization). The mechanical properties and crosslink densities of the cured XNBR films are determined and the influence of selected curing parameters is assessed. The results give evidence that a combined approach of thermal prevulcanization and photochemical postvulcanization makes the production of latex articles (e.g., gloves) with tailored properties and good skin compatibility feasible.

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In this work, functionalized damping layers consisting of crosslinked silicone rubber are incorporated into brittle epoxy-based composites to improve the delamination resistance of high voltage insulations. Selected functional organosilanes are attached onto the elastomer surface by a two-step modification to ensure a covalent bonding between the thermosetting resin and the damping layer. Functional model insulations and stator bar prototypes are then prepared with a vacuum pressure impregnation process. The influence of the damping layer on the thermo-mechanical and electrical properties as well as the delamination resistance is characterized. The results give evidence that the flexibility of the new composite materials can be increased significantly whereas the electrical properties are not affected by the elastomer layer. By evaluating the performance of the stator bar prototypes it can be clearly shown that both delamination resistance as well as high voltage endurance can be enhanced considerably by the application of flexible damping layers. POLYM. COMPOS., 00:000-000,