Ambient Blooming Behavior and Mechanical Properties of Vulcanized Natural Rubber Loaded with Non-Ionic Surfactants
This study investigated the ambient blooming behavior of additives and mechanical properties of vulcanized natural rubber (VNR) loaded with non-ionic surfactants coco diethanolamide (CDEA) and glycerol monostearate (GMS). Taguchi method and analysis of variance (ANOVA) were used to determine the significant main effects of additives on bloom rates and mechanical properties of VNR. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) spectra of VNR surface confirm the presence of chemical functional groups of stearic acid, paraffin wax, used oil, CDEA, and GMS. The amount of bloom (MB) versus square root of time (t1/2) plot yields two linear regions corresponding to distinct bloom rates which suggest that the blooming behavior of additives follows a non-Fickian mechanism. High loadings of stearic acid, used oil, and paraffin wax increase the bloom rates due to migration of excess unreacted additives to the surface of VNR. Also, additives easily diffuse out of the VNR due to softening of the rubber matrix. High loadings of sulfur and CDEA consistently decrease the bloom rates because of the increase in crosslink density and increase in filler dispersion, making it difficult for additives to bloom out of rubber matrix. High loading of sulfur significantly improves the tensile and compression moduli of VNR. Meanwhile, high loadings of ZnO and used oil significantly decrease the tensile and compression moduli of VNR. Sulfur as a crosslinking agent increases the crosslink density which resulted to increase mechanical properties. Excess used oil and zinc stearate, reaction product of ZnO and stearic acid, on the VNR matrix resulted to rubber matrix softening and decrease in mechanical properties.
Graeme E. Murch, Irina V. Belova and Andreas Öchsner
D. E. O. Santiago et al., "Ambient Blooming Behavior and Mechanical Properties of Vulcanized Natural Rubber Loaded with Non-Ionic Surfactants", Diffusion Foundations, Vol. 9, pp. 90-99, 2016