(1) Definition and origin
Spraying is a common quality problem in the processing of rubber stoppers. It refers to the phenomenon that the compounding agent contained in the unvulcanized rubber or vulcanized rubber migrates to the surface and precipitates. Sometimes, this kind of effluent is frosty crystal, so it is customary to say that “blooming” is more common in the sulphur, because sulphur is the most widely used vulcanizing agent in general rubber, and its solubility in rubber. Low and therefore easy to produce frost. In fact, from the appearance of the squirt, it may not always be frosty, but also oily (softener, plasticizer) or powdery (mostly fillers, anti-aging agents, accelerators, etc.) substances, even charcoal Black squirting is also seen.
(2) Reasons for the formation of frost
1 Over-mixing means that the amount of additives added to the rubber exceeds the limit acceptable for the rubber matrix, and the blooming occurs, which is a mistake in formulation design.
2 Under-sulfur sulphur squirting before the vulcanization of the rubber does not reach the pre-vulcanization (the sulphur ejected is free sulphur).
3 The aging cream product is partially aging (especially caused by light) during use, so that the auxiliary particles which have been adsorbed and fixed by the vulcanization network are detached from the rubber matrix and squirted outward.
4 Uneven products are damaged by uneven force during use, causing particles to squirt out through the damaged crack.
5 Cooling due to the large drop in the ambient temperature, the solubility of the compounding component in the rubber drops sharply, causing blooming. This type of spray is commonly found in winter rubber stoppers.
(3) The danger of blooming
1 It affects the appearance of the plug and becomes a quality defect. It has a great influence on the rubber stopper for daily use. It is often caused by the frosting to degrade or even scrap the product.
2 Reduce the adhesion of the rubber plug surface and affect the bonding strength with other parts.
3 In the case of semi-finished rubber products, the sprayed layer tends to affect the synthetic type and increase the processing difficulty.
(4) Why prevent blooming
1 Prevent the design formula when mastering the solubility of various additives in rubber to avoid over-matching. It is necessary to strengthen process management to prevent uneven dispersion and stress concentration due to poor mixing. During the storage and use of the product, long-term illumination and mechanical damage should be avoided to avoid the two factors inducing blooming.
2 Once the glue is found to be frosted, firstly, the sprayed material should be visually inspected or chemically analyzed to determine the chemical composition of the squirt and the cause of the frosting. Then, the right medicine should be taken and appropriate measures should be taken to prevent it from continuing to expand.
