(1) Rubber varieties
The origin of the return depends first on the rubber variety. Reversion occurs only in certain types of diene rubber, not all rubber types. However, it should also be noted that the amount of natural rubber and styrene-butadiene rubber is large, and most rubber grommets are made of these two rubbers. Butyl rubber is widely used in inner tubes and airtight products. Therefore, the reversion and anti-return problems of these kinds of glues are the most concerned.
(2) Crosslinked structure
In the sulfur vulcanization system, the amount of sulfur added plays a decisive role in the formation of a sulfur bond structure (monosulfide bond, disulfide bond or polysulfide bond). The more the amount of sulfur is used, the more the proportion of polysulfide bonds in the sulfur bond is, and the more serious the degree of reversion is. On the contrary, if the amount of sulfur is reduced to a certain extent by effective vulcanization, the mono- and disulfide bonds are dominant.
Due to their high bond energy, the phenomenon of reversion can be greatly reduced, and the anti-reversion property is obviously improved. Therefore, in the sulfur vulcanization system, the order of reversion from easy to difficult is: conventional vulcanization, semi-effective vulcanization, and effective vulcanization. Taking effective vulcanization as an example, the anti-reversion property is very abrupt. It is vulcanized at a temperature of 160 ° C, and generally does not return to the original, and a conventional vulcanization system is used, so that a high vulcanization temperature may cause serious reversion.
(3) Disappearance of cross-linking and chain scission
The rubber vulcanization curve has reached the stage of sulfur permeation and can be divided into two categories: one type is broken chain), natural rubber, isoprene rubber, styrene-butadiene rubber, etc., and the consequences are common reversion phenomena; The rubber type is mainly cross-linked, leading to another phenomenon, that is, the vulcanized rubber is hard, brittle, and elastic.