What is the surface of this performance? Rubber and its products in the process of processing, storage and use, due to the comprehensive role of internal and external factors caused by the gradual deterioration of the physical and chemical properties of rubber and mechanical properties, and finally lost the use value, this change is called rubber aging. On the surface of the performance of cracking, sticky, hardening, softening, powder, discoloration, mildew and so on.

Second, what are the factors that affect the aging of rubber?

　　The factors that cause the aging of rubber are:

(A) oxygen and oxygen in rubber with rubber molecules in the free base chain reaction, molecular chain fracture or excessive cross-linking, resulting in changes in rubber properties. Oxidation is one of the important reasons for rubber aging.

(B) The chemical activity of ozone and ozone is much higher and more destructive than that of oxygen, which also breaks the molecular chain, but the effect of ozone on rubber varies with the deformation of rubber. As rubber used for deformation (mainly unsaturated rubber), there is a crack perpendicular to the direction of stress, that is, the so-called "ozone cracking "; When acting on deformed rubber, only the surface produces an oxide film without cracking.

(C) Heat: Increasing the temperature can cause thermal cracking or thermal crosslinking of rubber. But the basic effect of heat is still the activation effect. It is a common aging phenomenon, thermal oxygen aging, to increase the rate of oxygen diffusion and activate the oxidation reaction, so as to accelerate the oxidation reaction speed of rubber.

(D) Light: the shorter the light wave, the greater the energy. What does damage to rubber is the high energy ultraviolet rays. In addition to directly causing the fracture and crosslinking of rubber molecular chains, rubber produces free radicals due to the absorption of light energy, which triggers and accelerates the oxidation chain reaction process. Ultraviolet light acts as a heating. Another characteristic of light acting (unlike thermal action) is that it is mainly born on the oak surface. The high glue content of the specimen, both sides will appear mesh cracks, that is, the so-called "light outer layer crack ".

(E) Mechanical stress: Under the repeated action of mechanical stress, the rubber molecular chain fracture will produce free radicals, trigger oxidation chain reaction, and form the chemical process of force. Mechanical fracture molecular chain and mechanical activation oxidation process. Which one can prevail depends on the conditions in which it is located. In addition, it is easy to cause ozone cracking under the action of stress.

(F) Moisture: the effect of moisture has two aspects: rubber in wet air rain or soak in water, easy to destroy, this is due to rubber water-soluble substances and water groups and other components are pumped dissolved. Caused by hydrolysis or absorption and other reasons. Especially in the alternating action of water immersion and atmospheric exposure, the damage of rubber will be accelerated. But in some cases, water is not damaging to rubber, and even has the effect of delaying aging.

(G) Other: The factors that act on rubber are chemical media, variable-price metal ions, high-energy radiation, electricity and biology.

Third, rubber aging test methods can be divided into which categories?

　　Can be divided into two broad categories:

(A) test methods for natural ageing.

　　It is divided into atmospheric old test, atmospheric accelerated aging experiment, natural storage aging test, natural medium (including buried land, etc.) and biological aging test.

(B) Manual accelerated Aging test method.

　　For thermal aging, ozone aging, light aging, artificial climate aging, light ozone aging, biological aging, high-energy radiation and electrical aging, as well as chemical media aging.

Four. Thermal Air Aging Test what temperature level should I choose for all kinds of rubber?

For natural rubber, the test temperature is usually 50~100℃, synthetic rubber is usually 50~150℃, and some special rubber test temperatures are higher. Such as Nitrile rubber with 70~150℃, silicone fluoride is generally used 200~300℃. In short, it should be specifically determined on the basis of the experiment.