Abstract: Excessive mixing of various additives has different solubility in rubber. The lower the solubility of additives in rubber, the more likely it is to cause excessive mixing and lead to frosting. The frost caused by excessive coordination often drives other groups to spray together, even though these sprays are far from saturated in the rubber.

The reason why rubber parts turn white on the outside is due to frost spraying!

Cause analysis:

Excessive cooperation

The solubility of various additives in rubber is also different. The lower the solubility of additives in rubber, the more likely it is to cause excessive mixing and lead to frosting. The frost caused by excessive coordination often drives other groups to spray together, even though these sprays are far from saturated in the rubber.

2. Changes in temperature

The solubility of additives in rubber usually changes with temperature. In this case, the solubility increases at high temperatures and gradually decreases at low temperatures. Due to the fact that rubber products are generally used at room temperature, once the external temperature is lower than room temperature, some additives in the formula may reach their solubility and produce frost. For example, rubber shoes produced in summer passed the factory inspection, but were found to have frost spray when stored in winter.

3 sulfur deficiency

The solubility of additives in rubber is affected by vulcanization. Taking NR as an example, under normal sulfurization conditions, the crosslink density is the highest, the free sulfur gradually decreases, and the probability of sulfur spraying also gradually decreases. The opportunity for other additives to shuttle through the three-dimensional network is also greatly reduced, so the probability of frost spraying will gradually decrease; On the contrary, in a sulfur deficient state, the network cross-linking density will be relatively low, and the probability of frost spraying will increase accordingly“