The vulcanization instrument measures the change of shear modulus of the rubber in the vulcanization process, and the shear modulus is proportional to the crosslinking density, so the measurement results reflect the change of the crosslinking degree of the rubber in the vulcanization process, and can measure the initial viscosity of the rubber, the coke time, the vulcanization rate, the positive vulcanization time and the persulfur reactivation.
The vulcanizer automatically records the torque value reflecting the shear strain generated by the rubber from the moment the rubber is fed into the mold. Thus, a curve of the relationship between torque and time is obtained, that is, the vulcanization curve. Its shape is related to the set test temperature and the characteristics of the compound.

1. What is vulcanization temperature
Rubber vulcanization temperature is one of the three elements of vulcanization, is the basic condition of rubber vulcanization reaction (crosslinking reaction), directly affects the vulcanization rate of rubber and the quality of products. Like all chemical reactions, the vulcanization reaction is accelerated with the increase of temperature, and it is easy to generate more low-sulfur crosslinking bonds. When the vulcanization temperature is low, the speed is slow, the generation efficiency is low, and more polysulfide cross-linking bonds are generated. The vulcanization temperature is generally applicable to van’t Hoff’s law, that is, for every 8-10 ℃ rise in temperature (about equivalent to the steam pressure of a gauge pressure), the reaction speed is about doubled; In other words, the reaction time is reduced by about half.

2. How to choose the vulcanization temperature
2.1 Types of rubber With the increase of room temperature vulcanization and the emergence of high temperature vulcanization, the vulcanization temperature tends to two trends. In terms of improving the vulcanization efficiency, it should be considered that the higher the vulcanization temperature, the better, but in fact, the vulcanization temperature can not be increased indefinitely. Rubber is a high molecular polymer, high temperature will cause the rubber molecular chain cracking reaction, resulting in the cross-linked bond break, that is, the phenomenon of “vulcanization return”, thus reducing the physical and mechanical properties of vulcanized rubber. For example, when natural rubber is vulcanized at high temperature, the activity of oxygen dissolved in rubber increases with the increase of temperature, causing strong oxidation, destroying the tissue of rubber, and reducing the physical and mechanical properties of vulcanized rubber.
2.2 Types of vulcanization systems in rubber formulations
According to the requirements of different properties of the final product, different vulcanization systems are selected for rubber formulations. The vulcanization system is different, the vulcanization characteristics are different, some need high activation temperature, and some need low activation temperature. Therefore, the corresponding vulcanization temperature should be selected according to the actual vulcanization system. Generally, the vulcanization temperature of the ordinary sulfur vulcanization system is 130-160 ° C, which needs to be determined according to the active temperature of the accelerator used and the physical and mechanical properties of the product.

When the active temperature of the accelerator is low or the product requires high strength, low fixed elongation stress and hardness, the vulcanization temperature can be selected to be lower, so that more polysulfide cross-linking bonds can be generated;
When the active temperature of the accelerator is higher or the product requires high fixed elongation stress and hardness, and low elongation, the vulcanization temperature should be higher, so that more low-sulfur cross-linked bonds can be generated.
Effective and semi-effective vulcanization systems, the vulcanization temperature is generally between 160-165 ° C, peroxides and resins and other non-sulfur vulcanization systems, the vulcanization temperature is suitable for 170-180 ° C. In particular, it should be pointed out that the formula of EPDM and NBR sulfur vulcanization, such as the design needs secondary sulfurization, the temperature and time of primary sulfurization and secondary sulfurization affect the compressive deformation and hardness of the final product. In the formula of peroxide vulcanization, the temperature of one-time sulfur is particularly important, the best temperature is above 180℃, if the temperature of one-time sulfur is insufficient, the effect of secondary sulfur supplementation is very low. That is, in the formula of peroxide vulcanization, secondary sulfurization has little effect on the final physical properties.