Synergistic effect of combined sulfur and glutaraldehyde curing system for natural rubber latex: Mechanical, thermal and thermo-mechanical properties

This study introduces a novel hybrid sulfur (S)/glutaraldehyde (GA) curing system, combining the high modulus and thermal stability of GA with the mechanical strength of S to optimize natural rubber (NR) vulcanizate performance. The influence of varying S/GA ratios (S100/GA0, S70/GA30, S50/GA50, S30/GA70 and S0/GA100) on the properties of NR vulcanizates were studied by using universal testing machine and Shore A durometer before and after thermal aging. Thermogravimetric analyzer together and temperature scanning stress relaxation (TSSR) were used to perform the thermal characterization. It was found that the synergistic effect on the S70/GA30 vulcanizate exhibited superior mechanical properties in terms of tensile strength and elongation at break at 14.19 MPa and 1,010%, respectively. On the other hand, the NR vulcanizates with a higher ratio of GA-latex compound (S30/GA70 and S0/GA100) showed the superior modulus, hardness and thermal stability. Furthermore, the relaxation behavior of the synergistic NR vulcanizates was studied by using the TSSR technique. It was found that the relaxation behavior of NR vulcanizates depends on the different levels of synergistic S/GA curing as a result of several types of linkages including, sulphidic linkages from S curing and GA linkages from GA curing. The obtained results are beneficial to apply this knowledge for developing various elastomeric products with desired properties. • NR latex was successfully vulcanized using various S/GA synergistic ratios. • S70/GA30 NR exhibits superior mechanical properties over individual S or GA. • Tensile strength and elongation at break improved at higher S levels. • High GA levels exhibited NR modulus, hardness, and thermal stability. • Findings help in developing elastomers with specific desired properties.