Track rubber grommets oxidation process

After thermal oxidation of natural rubber, it becomes soft and sticky, and its oxidation products include low molecular compounds such as carbon dioxide, formic acid, formaldehyde, acetic acid, levulinic acid and levulinic acid, and it can be concluded that it mainly undergoes chain degradation reaction. After thermal oxidation of the butadiene rubber, it becomes hard and brittle. Although an oxidation product such as a hydroxyl group and a carbonyl group is also detected, it can be concluded that it mainly occurs in chain crosslinking.

The above inference is further confirmed by chemical stress relaxation experiments on two rubbers. Since the crosslinked network regenerated after the oxidative degradation of the rubber grommets is not in a strain state, it does not contribute to the stress, so the number of breaks in the rubber mesh chain is reflected. The latter means that the sample is not stretched during the whole experiment, and is only stretched when the stress is measured. Immediately after the stress is measured, the external force is released, that is, the sample is always in the intermittent stress relaxation state, and the stress reflected by the curve It is jointly undertaken by the new and old cross-linking networks. It can be seen that the difference between the intermittent stress relaxation and the continuous stress relaxation is a measure of the degree of crosslinking during oxidation. Natural rubber has an advantage in the breakage of the network chain during the observation period of thermal oxygen aging. In the observation time of thermal oxygen aging, the early stage of the rubber is mainly the fracture of the net chain, and the later stage is mainly the generation of new cross-linking. In general, cross-linking is the mainstay. The alkane radicals RO- formed during the oxidation of butadiene rubber cause macromolecular chain degradation. Chemical bonding is also formed between the oxidative degradation products.