In vulcanization of rubber products, the vulcanization medium is a kind of heating medium, and the vulcanization medium is required to have good heat conductivity and dispersibility, and has a high heat storage capacity. Commonly used vulcanization media are water, air, steam (saturated steam and superheated steam) and other solid media, which are common methods for producing rubber sheets and rubber floors.
1. Saturated steam At present, one of the most widely used vulcanization media has its heat from latent heat of vaporization, which has the advantages of large thermal coefficient, high thermal conductivity, large heat dissipation, easy operation, and low cost. With direct saturation and steam vulcanization, the air in the vulcanization vessel can be discharged, reducing the damaging effect of oxygen in the air on the rubber. The disadvantage is that it is easy to generate condensed water, the temperature in the large-scale vulcanization tank is not uniform, the local temperature is low, and the heat medium for fear of water products is not suitable.
2. Superheated steam Superheated steam can be obtained by passing saturated steam through a heater. The superheated steam has less condensed water and the temperature in the tank is not contained by the pressure. It is suitable for a vulcanizing medium with a high vulcanization temperature. The disadvantage is that the equipment is heavily corroded.
3. Hot air Hot air vulcanization can be carried out under normal pressure or under pressure. The advantage is that the heating temperature is not affected by the pressure, does not contain moisture, and is relatively dry. Hot air vulcanized products have a smooth surface and a good appearance. Some special rubbers such as urethane rubber are susceptible to hydrolysis and require hot air vulcanization. Disadvantages are low heat-transfer coefficient, low heat-conducting efficiency, and vulcanization time that is twice as long as vulcanization with steam. At the same time, air contains a lot of oxygen, especially at high temperature, it is easy to oxidize the product.