Due to the different hardness and softness of products, different product structure, the product temperature is too high will appear adverse phenomenon, such as bursting edge, blowing bubble, too brittle and other phenomena, so some products will use low-temperature vulcanization, the most important reason is too fragile prone to burst edge phenomenon!
The main factors influencing the curing process are sulfur content, curing temperature and curing time.
Sulphur dosage. The greater the dosage, the faster the vulcanization rate and the higher the degree of vulcanization can be achieved. Sulfur in rubber solubility is limited, excess sulfur will be precipitated from the surface of the rubber, commonly known as "sulfur spray." To reduce sulphur spraying, it is required to add sulphur at the lowest possible temperature, or at least below the melting point of sulphur. According to the use requirements of rubber products, the amount of sulfur in soft rubber generally does not exceed 3%, the amount in semi-hard glue is generally about 20%, and the amount in the condition of hard glue vulcanization can be as high as more than 40%.
Curing temperature. If the temperature is higher than 10℃, the curing time is reduced by half. As rubber is a bad heat conductor, the vulcanization process of the product is different due to the temperature difference of its various parts. In order to ensure a more uniform degree of vulcanization, thick rubber products are generally used to heat up gradually, low temperature for a long time vulcanization.