The Application Of Organic Zinc In Natural Rubber

Organic zinc could improve the processing fluidity property and curing characteristics of rubber materials.In this paper,fatty acid zinc with different structure was prepared to research the influence of the molecular structure of fatty acid zinc on NR processing fluidity performance,curing characteristics and physical and mechanical properties.The fatty acid zinc and the organic alcohol zinc were used together to study the effect and mechanism of the combination use of organic zinc on the curing characteristics.Fatty acid and zinc oxide were used to prepare zinc laurate,zinc myristate,zinc palmitate,zinc stearate and zinc oleate by melting method.The molecular structure,phase transition,crystal structure and crystal morphology of the product were characterized and analyzed by FT-IR,DSC,XRD and POM.The results indicated that fatty acid zinc was prepared successfully.The results showed that the crystal layer spacing and intermolecular forces were raised when the chain length of saturated fatty acid zinc increased.The crystal phase of zinc laurate was loose and the crystal size of zinc oleate was small.The effects of the addition amount of saturated zinc stearate and unsaturated zinc oleate on the NR composites were compared and the effect of the chain length of saturated fatty acid zinc on the NR composites was studied.The results showed that zinc stearate could increase the crosslink density and physical and mechanical properties of the NR composites and zinc oleate could reduce the Mooney viscosity of the NR composites and improve the filler dispersion.The processing fluidity property and filler dispersion were improved and the physical and mechanical properties of vulcanizates were not significantly different when the saturated fatty acid zinc chain length was shortened.The compatibility and curing activity of zinc laurate,zinc stearate and zinc oleate in the NR matrix were characterized by SEM,DSC,RPA and rheometer test.Zinc laurate was most compatible with the NR matrix due to the loose crystalline phase and the lower van der Waals force between the molecules and the crystallinity in the NR matrix.The SEM test result showed that zinc oleate was microscopically separated in the NR matrix.The curing activity of zinc stearate was lower than that of zinc laurate revealed by rheometer and DSC tests because that van der Waals force between the zinc stearate molecules and the electron cloud density of Zn was larger and its compatibility with the NR matrix was poorer.In addition,the curing activity of zinc glycerolate was significantly higher than that of fatty acid zinc.The effect of the combination of zinc glycerolate and zinc laurate on the performance of the NR composites was studied.The outer shell electron cloud density of Zn in zinc glycerolate was lower than that of zinc laurate as was shown by XPS test.Moreover,the steric hindrance of Zn in zinc glycerolate was lower.The tc₁₀ and tc₉₀ were shorter and crosslink density was higher,but the resistance to reversion was poorer when the NR composites were prepared by zinc glycerolate alone.The combination of zinc glycerolate and zinc laurate increased Ozawa and Kissinger vulcanization activation energy and improved anti-reversion property performance.Meanwhile,the incorporation of zinc laurate endowed the NR composites with considerable improvements in the processing fluidity and filler dispersion.Besides,the obvious decrease in the rolling resistance was achieved with the combination of zinc glycerolate and zinc laurate.The combination of zinc glycerolate and zinc laurate effectively reduced the amount of zinc in the NR composites.Finally,the effect of zinc pentaerythritol,zinc acetylacetonate and their combination with zinc laurate on the performance of the NR composites was studied.XPS test was shown that the outer shell electron cloud density of Zn in zinc acetylacetonate was higher.Moreover,the steric hindrance of Zn in zinc acetylacetonate was larger and its curing activity was lower.Zinc pentaerythritol possessed higher curing activity.However,when the both were used as curing activators alone,the anti-reversion performance of the NR composites was poorer.Their combination with zinc laurate improved the anti-reversion property and physical and mechanical properties.At the same time,the amount of zinc was obviously reduced.