Extrusion molding processes are generally vulcanized by hot air, steam or liquid media. Hot air vulcanization generally adopts a hot drying tunnel, the drying tunnel temperature is 300-650 ℃, and the curing time is 3-12 seconds. The recommended curing agent is bis-24 or an addition type curing agent, both of which can provide fast curing performance without generating air bubbles.
Steam vulcanization is usually used in the processing of wires and cables. The diameter of the steam box is 100-150mm, the length is 30-50m, the steam pressure is 3.5-15bar, the liquid medium is vulcanized, and the extruded silica gel is usually immersed in the molten liquid (salt or lead). Double 24 is used to avoid air bubbles.
The purpose of the primary vulcanization process is to remove the by-products produced during the vulcanization process of the low-volatiles and perchloride vulcanizing agents in the silica gel. Secondary vulcanization can make the product more dimensionally stable and improve its temperature resistance. For production processes that use peroxides as vulcanizing agents; secondary vulcanization is recommended to remove acidic by-products, especially when the final application ambient temperature is high. Both electrically heated and high temperature gas heated ovens can be used successfully in the secondary vulcanization process. For every 100kg of silicone products, it is recommended to maintain at least 100L/min of air flow in the oven. During the secondary vulcanization process, try to increase the exposed area of the product, and it is recommended that the oven set temperature is at least about 100°C higher than the actual operating temperature. For products with a thickness of more than 2mm, it is recommended to use the method of gradually increasing the temperature to reduce the problem of blistering on the surface of the product.