The ozone aging test chamber is an experimental instrument for evaluating rubber aging. QINSUN Instruments Co., Ltd. is the manufacturer. Customers in need are welcome to inquire. In addition, the structural changes of rubber in the thermo-oxidative aging process can be divided into two categories: one is the thermo-oxidative aging reaction (cracking), mainly based on the breakdown of molecular chains; the other is mainly the cross-linking between molecular chains Thermo-oxidative aging (structuring).
Natural rubber contains isoprene rubber, butyl rubber, binary ethylene propylene rubber, homopolymerized chlorohydrin rubber and copolychlorohydrin rubber. The appearance of this type of rubber after thermo-oxidative aging is soft and tacky.
The rubber containing butadiene in butadiene mainly undergoes cross-linking reaction during the thermo-oxidative aging process. Similar rubber typesn include NBR/SBR/CR/ERDM/FPM/CSM and so on. The appearance of this type of rubber after thermo-oxidative aging is hardened and brittle.
The main factors influencing the aging of rubber are:
1. Oxygen: Oxygen in rubber is linked to free radical rubber molecules Reaction, molecular chain breakage or excessive cross-linking, changing the rubber properties. Oxidation is one of the main reasons for rubber aging.
2. 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 varies depending on whether the rubber is deformed or not. When used on deformed rubber (primarily unsaturated rubber), cracks occur in the direction of stress, so-called ozone cracking; when used on deformed rubber, only an oxide film formed on the surface without cracking.
3. Heat: Increasing the temperature can cause thermal cracking or thermal cross-linking of rubber. But the basic effect heat is activation. Increase the oxygen diffusion rate and activate the oxidation reaction, accelerating the rubber oxidation reaction rate, which is a common aging phenomenon - thermal oxygen aging.
4. Mechanical stress: Under the repeated action of mechanical stress, the molecular chain of rubber will be broken to form free quan, which will activate the oxidation chain reaction and form a mechanochemical process. Mechanical breaking of molecular chains and mechanical activation of oxidation processes. Which one has an advantage depends on the circumstances it is in. In addition, it is easy to cause ozone cracks under stress.
5. Moisture: The role of moisture has two aspects: when it becomes rubber bexposed to rain in humid air or soaked in water for a long time, it is easy to damage, which is due to the water-soluble substances and hydrophilic groups in the rubber, etc. The ingredients are extracted and dissolved by water, hydrolyzed or absorbed. Especially under the alternating action of immersion in water and exposure to the atmosphere, the destruction of rubber will be accelerated. However, under certain conditions, moisture does not damage the rubber and even has a retarding effect on aging.
6. Oil: If it is in contact with oil medium for a long time during use, the oil may penetrate into the inside of the rubber to cause swelling, resulting in a decrease in the strength and other mechanical properties of the rubber. The oil can cause the rubber to swell, because after the oil penetrates into the rubber, the molecular diffusion occurs, the network structure of filledlcanized rubber changes.
7. Others: There are chemical media, Variation of metal ions, high energy radiation, electricity and biology, etc.
Rubber aging protection method:
Since rubber aging is a complex and comprehensive chemical reaction process, and it is impossible to prevent rubber aging, rubber aging can being. Take appropriate measures to slow down the aging rate of rubber, so as to achieve the purpose of extending the service life of rubber. Anti-aging measures mainly include physical protection and chemical protection.
The physical protection method refers to avoiding the interaction between rubber and various aging factors as much as possible, such as using a surface coating or treatment, adding a light barrier agent, adding paraffin, etc.