What are the factors that affect the tear strength of prosthetic silicone?

What are the factors that affect the tear strength of prosthetic silicone?
The factors that affect the tear strength of prosthetic silicone are mainly the following:
Material characteristics:
Hardness: Generally speaking, the harder the silicone, the higher the tear strength. Because higher hardness means stronger intermolecular forces, the structure is relatively more stable, and it is less likely to be destroyed when subjected to tearing force.
Raw material formula: The type and content of vulcanizer and cross-linking agent in silicone determine the cross-linking density of silicone, which has a significant impact on tear strength. A reasonable formula can allow silicone to form a moderate and uniform cross-linking structure, improving the ability to resist tearing; if the formula is unreasonable, the cross-linking is insufficient or the cross-linking density is low, the tear strength of silicone will decrease.
Product shape and structure:
Thickness: When the thickness of silicone material is large, its core part will be subjected to greater stress, which is easy to cause damage to the internal structure when subjected to force, making the material easier to tear.
Defects: If there are cuts, holes, flaws or impurities in silicone products, these places will become stress concentration points. When subjected to external force, stress will accumulate at these defects, making it easier for tearing to start and expand from these locations, thereby significantly reducing the tear strength of silicone.
Production process:
Mixing process: Factors such as the temperature, time and degree of mixing during mixing will affect the uniform distribution of various components in the silicone and the state of the molecular chain. If the mixing is not uniform, the silicone performance will be inconsistent and the tear strength of some areas will be reduced; excessive mixing may damage the molecular chain, which is also not conducive to the improvement of tear strength.
Vulcanization process: The temperature, pressure and time of vulcanization are crucial to the cross-linking reaction of silicone. Appropriate vulcanization conditions can promote the silicone to form a good cross-linking structure and improve the tear strength; if the vulcanization is insufficient, the silicone cross-linking is incomplete and the strength is low; if the vulcanization is excessive, the silicone will become brittle and its tear resistance will be reduced.
Use environment and method:
Environmental factors: Long-term exposure to high temperature, low temperature, high humidity or chemical corrosive substances will cause the molecular structure of silicone to change, leading to aging, and thus reducing its tear strength. For example, high temperature will accelerate the degradation of molecular chains, and chemicals may react with silicone to destroy its original structure.
Usage: If the prosthetic silicone is often subjected to improper external forces such as excessive stretching, twisting, or scratching by sharp objects during use, it will accelerate the wear and damage of the silicone and reduce its tear strength.