High constant tensile rubber: neoprene, nitrile rubber, polyurethane rubber, crystalline rubber such as natural rubber, etc.
* Whether it is pure rubber or filled vulcanizate, as the crosslink density increases, the elongation stress and hardness also increase linearly.
The size of the crosslinking density is usually achieved by adjusting the types and dosages of the vulcanizing agent, accelerator, co-vulcanizing agent, and active agent in the vulcanizing system.

Some accelerators have only one function, and some accelerators have multiple functions; such as thiurams, guanidines and sulfenamides, the activity is very high. The vulcanizate has a relatively high tensile stress.
TMTD has a variety of functions, and has both activation, promotion and vulcanization, so TMTD can effectively increase the elongation stress.

In the formulation design, in order to keep the vulcanizate's constant elongation stress constant, it is necessary to reduce the amount of polysulfide bonds and reduce the amount of sulfur, so the amount of accelerator should be increased. The product of the amount of sulfur and the amount of accelerator )keep constant.

Relationship between filling system and fixed elongation stress:
* Different types of fillers have different effects on the vulcanizate's elongation stress and hardness: fillers with small particle size and high activity, vulcanizate's elongation and hardness increase greatly. With the increase of filler amount, the elongation stress And hardness also increases.
* High structural carbon black also has high elongation stress.
* In general, the hardness of vulcanizates increases with the amount of filler.