Thermal aging of rubber grommets

The phenomenon that rubber or rubber grommets are aged during storage or use due to both heat and oxygen in the air is called thermal oxygen aging. Thermo-oxidative aging is the aging of various rubbers all the time, which is the main cause of damage to rubber grommets. The rubber undergoes thermal oxygen aging at temperatures below 200 ° C. Oxygen is the main cause of aging, and heat only acts to activate oxidation and accelerate oxidation.

However, at a high temperature of 200 ° C or higher, the action of thermal energy alone is sufficient to degrade the rubber macromolecular chain. The more the temperature is, the more thermal degradation is dominant, and the thermal degradation becomes the main cause of rubber damage. Whether it is thermal oxidation or thermal degradation can not be eliminated, but can try to delay their occurrence, so that rubber grommets maximize their use value. To this end, we should understand the mechanism of oxidation and thermal degradation of rubber and its effects.

Oxidation reaction mechanism of rubber grommets

Oxygen is a reactive element that reacts easily with unsaturated rubber under normal conditions and reacts with saturated rubber at temperatures or under certain conditions. After the unsaturated rubber is oxidized, the mechanical properties change significantly. For example, 1 g of natural rubber vulcanizate absorbs oxygen at 20 ° C at 110 ° C, and its tensile strength decreases by 3/4, and oxygen is absorbed by 3 cm 3 at 120 ° C, and the stress relaxation rate is accelerated by 2 times. Therefore, the study of the rubber oxidation mechanism begins with unsaturated natural rubber. It is found that the oxidation of unsaturated carbon chain rubber is carried out according to the mechanism of free radical chain reaction. The reaction has an autocatalytic characteristic: the main product in the reaction is hydrogen peroxide, which plays an automatic catalytic role for oxidation.