Dual crosslinking of carboxylated nitrile butadiene rubber latex employing the thiol-ene photoreaction

• Published in: Journal of applied polymer science Vol. 129; no. 5; pp. 2735 - 2743
• Main Authors: Lenko, Dietmar, Schlögl, Sandra, Temel, Armin, Schaller, Raimund, Holzner, Armin, Kern, Wolfgang
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 05.09.2013; Wiley; Wiley Subscription Services, Inc
• Subjects: Applied sciences; Butadiene; Crosslinking; Crosslinking and degradation; Curing; elastomers; Exact sciences and technology; Gloves; Latex; Materials science; Mechanical properties; Nitriles; Photochemical; photochemistry; Physicochemistry of polymers; Polymers; Polymers and radiations; Photochemical crosslinking; Molecular structure; Crosslink density; Mechanical properties; Tensile property; Photochemical reaction; Nitrile rubber; Experimental study; Latex; Solvent resistance; Vulcanization; Ultraviolet radiation; Vulcanizate; elastomers; photochemistry; Concentration effect; Reaction mechanism; Zinc oxide; Acid copolymer; Chemical properties; crosslinking
• ISSN: 0021-8995; 1097-4628
• DOI: 10.1002/app.38983

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 CC 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. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013