engleski

Degradation Velocity of Natural Rubber Films

Successful substitution of accelerator, zinc diethyldithiocarbamate (ZDEC) in sulfur cured natural rubber latex films with the combination of two other accelerators, zinc mercaptobenzothiazole (ZMBT) and diphenylguanidine (DPG) was investigated by following the degradation velocity of the monitoring samples. Commonly used ZDEC in latex compounds produces secondary amines which may react with present NO2 and give N-nitrosoamines which are recognized as cancerous substances. Investigations of photooxidation and thermooxidation on fully formulated natural rubber latex films, including protective agent, were carried out. Degradation of latex films were followed by IR spectroscopy, measuring the increase of absorbance of hydroxyl and carbonyl groups with time. Physical and mechanical properties were also determined by stress-strain measurement. According to the results, thermodegradation of latex films is not intensive as photodegradation processes, specially at early stages of the degradation. Parallel with thermooxidation of latex films, additional processes such as crosslinking can be observed. At the onset of thermooxidation usually small addition crosslinking effect may be noticed, arising from polysulphide links rearrangement, and this contributes to an increase of specimens tensile strength. All obtained results show that mentioned accelerators substitution is a reasonable approach to environmental issues in production of natural rubber latex goods and commodity, as well as technical parts.

Accelerators;degradation;natural rubber films;photooxidation;polysulphide links;thermooxidation

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