Sulfur usage. The greater the amount, the faster the vulcanization rate, the higher the degree of vulcanization can be achieved. The solubility of sulfur in rubber is limited, and excessive sulfur will be precipitated from the surface of the rubber material, commonly known as "sulfur spraying". In order to reduce sulfur spraying, it is required to add sulfur at the lowest possible temperature, or at least below the melting point of sulfur. According to the requirements of the use of rubber products, the amount of sulfur in soft rubber is generally not more than 3%, the amount in semi-ebonite is generally about 20%, and the amount in ebonite can be as high as more than 40%.
Vulcanization temperature. If the temperature is 10℃ higher, the vulcanization time is reduced by about half. Because rubber is a poor heat conductor, the vulcanization process of the product is different due to the difference in temperature of its various parts. In order to ensure a more uniform degree of vulcanization, thick rubber products are generally gradually heated up and vulcanized at low temperature for a long time.