Accelerated vulcanisation of natural rubber latex sheets using microwave energy: Mechanical and thermal performance improvements

• Microwave pre-vulcanisation reduces processing time by up to 40 times. • Optimal microwave conditions: 80 watts for 30-90 seconds ensure efficiency. • Superior tear strength and heat resistance achieved with microwave treatment. • Microwave-treated rubber forms stable mono- and di-sulfidic crosslinks. This study investigates microwave-assisted post-vulcanisation as a time-efficient alternative to conventional oven curing for natural rubber (NR) latex sheets. NR latex compounds were pre-vulcanised using microwave radiation at 80 W for durations of 30-90 seconds and compared with oven-vulcanised counterparts at 60°C for 1200-1800 seconds. Microwave treatment significantly accelerated water evaporation, achieving up to 5.5 times faster moisture removal rates. The samples vulcanised for 90 seconds (MW-90) exhibited superior crosslinking characteristics, including lower solvent uptake, higher crosslink density, and enhanced tear strength compared to oven-cured samples. Tensile strength and density values remained comparable across both curing methods. Thermal ageing tests demonstrated that MW-90 samples retained the highest relative tensile strength, attributed to a higher proportion of mono- and di-sulfidic crosslinks, as confirmed by Mooney-Rivlin analysis. These findings highlight microwave vulcanisation as a sustainable, time-saving approach capable of delivering mechanical and thermal properties equivalent to or exceeding conventional thermal vulcanisation, with significant potential for industrial latex applications.