A study on preservatives on the structure and properties of natural rubber latex

The preservative of natural rubber latex (NRL) is essentially a kind of bactericide or bacteriostat, mainly used for sterilisation or inhibit bacterial breeding, which will improve the pH of latex. To maintain the colloidal stability and consider the needs of reality manufacture, the NRL preservative also needs to have the advantages in terms of low price, ease to obtain and use, low toxicity, etc. In this study, a derivative of s-triazine (HT), a derivative of 2-methyl-4-isothiazolin-3-one (MI) and 2-methyl-5-chloro-4-isothiazolin-3-one (CMI) mixture (KS) are chosen as a non-ammonia preservative for NRL, which their effect on the structure and properties of NRL was investigated. The results of vulcanisation characteristics showed that the temperature dependence of the samples preserved by preservative HT was lower than that of ammonia and KS during the induction period (t₁₀). The test results of molecular weight and cross-linking density showed that the addition of preservative HT could protect the molecular chain structure of NR. In terms of physical and mechanical properties, the performance of sample HT is similar to that of sample ammonia, but after thermo-oxidative ageing at 100 °C for 24 h, the tensile strength retention rate of the sample preserved by the preservative HT can still reach 78%, which is higher than that of the ammonia preserved sample. Therefore, Preservative HT is a relatively better preservative. Its addition will not affect the structure of NRL and the prepared NR has good physical and mechanical properties as well as thermo-oxidative resistance. It can be considered to replace ammonia as the NRL preservative.