Research On New Non-ammonia Preservative For NR Latex

Fresh natural rubber (NR) latex spontaneously putrefies and coagulates within4to6hours from its collection from the trees, a process which is non-desired because it renders further handling of the latex more difficult or hardly possible and hence economically non-attractive. Accordingly, to avoid problems associated with a non-desired coagulation of the NR latex during the collection, pooling and concentration by centrifugation, as well as to avoid putrefaction, the addition of preservative were applied to preserve NR latex. And ammonia water (NH3·H2O) has been the most common preservative for preserving NR latex in industry. However, the use of ammonia also presents several disadvantages. NR latex putrefies easily because of weak sterilization capability of ammonia. And ammonia evaporates easily, the emission of the ammonia fumes makes the working environment very unpleasant for the workers or other personnel and may indeed be injurious or hazardous to their health. Another problem arising from the emission of ammonia fumes relates to corrosion of factory buildings and roofs. Moreover, because ammonia is alkaline, the amount of acid coagulating latex increases.HT, one environmental, efficient and broad-spectrum bactericide, was used to be the preservative for NR latex. The preservation effect of HT were evaluated through detecting VFANo, MST, η and pH of NR latex preserved by HT. Effect of HT and storage time on NR chemical structure, six properties index, cure characteristics and processing properties were investigated. Studies about mechanical properties, dynamic mechanical properties and thermal-oxidative stability of NR vulcanizates and concentrated NR latex vulcanized films were did.The results indicated that HT preserve fresh NR latex (HL) could be stored effectively, not to putrefy or coagulate for120hours, and NR chemical structure of HL were the same as ammonia preserve fresh NR latex (NL). The six properties index of NR from HL (HL-NR) confirmed to GB/T8081-2008, and PRI of HL-NR were10.0higher than NR from NL (NL-NR), indicating more excellent thermal resistance properties. The viscoelasticity of HL-NR were the same as NL-NR. Meanwhile, there was favourable synergy between HL-NR and vulcanizing ingredients, and the vulcanizing reaction rate of HL-NR were slightly higher than that of NL-NR. Mechanical properties of HL-NR were greatly excellent, the tensile strength and tear strength were about5MPa and5KN·m-1respectively higher that of NL-NR. DMA tests showed glass transition temperature of HL-NR and NL-NR were very close. TG tests indicated that thermal-oxidative stability of HL-NR were slightly poorer, but the mechanical properties after aging were still excellent.Analysis results of VFANo, MST, η and pH suggested that concentrated latex could be more effectively preserved by HT than by ammonia for90days, and there was no chemical changes in rubber molecule chain of HT preserve concentrated NR latex (HCL) during storage, the chemical structure of HCL were the same as ammonia preserve concentrated NR latex (NCL). Not only toughness of HCL vulcanized films was better than that of NCL vulcanized films, but also tensile strength, tear strength and elongation at break of HCL vulcanized films were all higher than that of NCL vulcanized films. DMA and TG tests indicated that frost resisting ability under low temperature and thermal-oxidative stability of HCL vulcanized films were both slightly higher than that of NCL vulcanized films.