What are the factors that cause the aging of the polyurethane?

1. Mechanical force: Under repeated mechanical force, the polyurethane encapsulated molecular chain will be broken to generate free radicals, which will initiate oxidation chain reaction and form a mechanochemical process. In addition, it is easy to cause ozone cracking under stress.

2. Light: UV rays with higher energy are the damage to the product. The shorter the light wave, the greater the energy. In addition to directly causing the breakage and cross-linking of the molecular chain, free radicals can also be generated due to the absorption of light energy, which initiates and accelerates the oxidation chain reaction process. For samples with high gel content, network cracks will appear on both sides, the so-called "light outer layer cracks".

3. Oil: If it is in long-term contact with oily medium during use, the oil can penetrate into its interior and cause it to swell, resulting in a decrease in strength and other mechanical properties.

4. Moisture: It is easy to age when it is exposed to rain or soaked in humid air, especially under the alternating action of water soaking and atmospheric exposure, it will accelerate the damage.

5. Heat: Too high temperature will cause thermal cracking or thermal cross-linking of the encapsulated product. But the basic function of heat is activation. This is a common aging phenomenon-thermal oxygen aging.