Effect of Curing Temperature on the Chemical and Mechanical Properties of Natural Rubber from Accelerator-Free Vulcanization Catalyzed by Dicumyl Peroxide

Natural rubber films, commonly crosslinked using sulfur and accelerators such as zinc diethyldithiocarbamate (ZDEC), zinc-2-mercaptobenzothiazole (ZMBT), and tetramethylthiuram disulfide (TMTD), have been implicated in allergic reactions on human skin.To mitigate these effects, an alternative crosslinking system using peroxides has been proposed.While preliminary studies have shown that this peroxide system can produce satisfactory films, mechanical properties such as film strength have yet to be optimized.This study aims to enhance the mechanical properties of natural rubber films by eliminating accelerators from the formulation and employing peroxide crosslinking.Dicumyl peroxide, a long-chain organic peroxide, was selected for vulcanization to replace accelerators.Three different concentrations of dicumyl peroxide (1.5, 2.0, and 4.0 phr) were tested with continuous stirring for 48 hours.Curing of the latex films was performed at three different temperatures (100, 120 and 140 C) to identify the optimal drying temperature.The latex films underwent FTIR analysis to determine their chemical characteristics.FTIR analysis of the latex films containing dicumyl peroxide revealed characteristic peaks indicative of successful crosslinking, including C-H symmetric stretching vibrations and distinctive bands around 2964 cm -1 representing asymmetrical and symmetrical stretching modes of methyl groups.Tensile tests were conducted to assess the maximum tensile strength.There were notable trends in tensile strength, with the control set exhibiting an increase in strength up to 12.1 MPa at 140 C, while sets containing dicumyl peroxide approached similar strengths to the control set at 100 C.The results demonstrate the effectiveness of dicumyl peroxide in improving the properties of latex films and facilitating the production of allergen-free latex films with satisfactory mechanical characteristics.The tensile strength findings revealed significant variations across different curing temperatures and dicumyl peroxide concentrations, with sets containing dicumyl peroxide exhibiting comparable strength with the control set.By eliminating accelerators from the formulation and applying peroxide crosslinking, this study offers a promising avenue for mitigating allergic reactions on human skin caused by conventional sulfur-based vulcanization methods.