Evaluation of suitability of urea as a preservative in low ammonia centrifuged natural rubber latex

Research at a glance

Low ammonia centrifuged natural rubber latex is generally preserved with the secondary preservative system, tetramethyl thiuram disulphide (TMTD) and zinc oxide (ZnO). This system is known to be carcinogenic due to the generation of nitrosamines. Hence the aim of this study was to evaluate the suitability of urea as an alternative for the TMTD/ZnO preservative system. Field latex was treated with the TMTD/ZnO system (Control) and varying quantities of urea to produce centrifuged latex. Latex was stored for 0, 15, 45 and 60 days and characterized. Physico-mechanical properties and resistance to thermal degradation were evaluated using cast latex films. The standard test for total extractable proteins, GC/MS analysis for nitrosamines and the standard microbiological examination were conducted. For urea treated latex, most of the characteristics were in accordance with the ISO specifications. Physical properties of the cast films produced with this latex were in accordance with the requirement for cast films. Aging studies of these films indicated higher resistance to thermal degradation than the Control. Also, a marked reduction in the total extractable protein content was observed in comparison to the Control. Microbiological examination further implies the suitability of urea as a preservative agent. In the GC/MS analysis, peaks accountable for N-Nitrosodibutylamine were identified only in the spectrum of the film produced with TMTD/ ZnO system, but not in those produced with urea. Results in overall showed that urea, which does not indicate generation of nitrosamines could be an alternative for the TMTD/ZnO preservative system. The 0.021% urea treated latex sample and its cast film showed the best properties.