What Are The Factors Of Aging Rubber Products?
A) Oxygen: Oxygen undergoes a free radical chain reaction with rubber molecules in the rubber, and the molecular chain is broken or excessively crosslinked, causing a change in rubber properties. Oxidation is one of the important reasons for rubber aging.
B) Ozone: The chemical activity of ozone is much higher than that of oxygen, and it is more destructive. It also breaks the molecular chain, but the effect of ozone on rubber is different depending on whether the rubber is deformed or not. When it is used as a rubber for deformation (mainly unsaturated rubber), a crack which is straight in the direction of stress is generated, that is, "ozone cracking"; when it acts on a deformed rubber, only an oxide film is formed on the surface without cracking.
C) Heat: Increasing the temperature can cause thermal cracking or thermal crosslinking of the rubber. But the basic role of heat is activation. Increasing the rate of oxygen diffusion and activating the oxidation reaction to accelerate the oxidation reaction rate of the rubber is a ubiquitous phenomenon of aging - thermal aging.
D) Light: The shorter the light wave, the greater the energy. What is damaging to rubber is the higher energy of ultraviolet light. In addition to ultraviolet rays directly causing the breakage and cross-linking of rubber molecular chains, rubber generates free radicals by absorbing light energy, which initiates and accelerates the oxidation chain reaction process. The external light acts as a heating. Another characteristic of light action (different from heat) is that it mainly grows on the surface of the oak. For samples with high gel content, there will be reticular cracks on both sides, the so-called "outer layer cracking".
E) Mechanical stress: Under the repeated action of mechanical stress, the rubber molecular chain will be broken to form free enthalpy, which will initiate the oxidative chain reaction and form a force chemical process. Mechanically broken molecular chains and mechanically activated oxidation processes. Which one can prevail depends on the conditions in which it is located. In addition, it is easy to cause ozone cracking under stress.
F) Moisture: There are two aspects to the effect of moisture: when the rubber is exposed to humid air or immersed in water, it is easily destroyed. This is because the water-soluble substances and hydrophilic groups in the rubber are dissolved and dissolved by water. Or caused by absorption and other reasons. Especially in the alternating action of water immersion and atmospheric exposure, the rubber damage will be accelerated. However, under certain circumstances, moisture does not have a destructive effect on rubber, and even has the effect of delaying aging.
G) Oil: If it is in contact with the oil medium for a long period of time during use, the oil can penetrate into the rubber to cause swelling, resulting in a decrease in the strength and other mechanical properties of the rubber. The oil can swell the rubber because the oil penetrates into the rubber, and the molecules are mutually diffused, and the network structure of the vulcanized rubber changes.
H) Others: The chemical factors, such as chemical media, variable metal ions, high-energy radiation, electricity and biology.