In the process of processing, storage and use of rubber and its products, due to the comprehensive action of internal and external factors, the physical and chemical properties and mechanical properties of the rubber are gradually deteriorated, and the use value is lost at last. This change is called rubber aging, which is characterized by cracking, stickiness, hardening, softening, chalking, discoloration, mildew, etc.
Ozone mainly exists in the ozone layer below the stratosphere in the atmosphere (20 kilometers away from the surface), but there is also rare ozone in the surface atmosphere (mainly from natural discharge phenomena such as lightning and photochemical reactions: NOx in automobile exhaust is The formation of free oxygen combined with oxygen molecules to form ozone under UV irradiation). Because some plastic materials and most rubber materials are sensitive to ozone, even thin ozone will cause cracks in some plastic materials and most rubber materials. To deal with this problem, it is very important to test ozone aging.
The content of ozone in the atmosphere is very small but it is the main factor for rubber cracking. The ozone aging test chamber manufacturered by Guangdonng Yuanyao Test Equipment, simulates and strengthens the ozone conditions in the atmosphere, studies the law of the action of ozone on rubber, and quickly identifies and evaluates the ozone aging resistance and resistance of rubber Ozone and ozone protection test methods, and effective anti-aging measures are adopted to improve the replacement of rubber products. There are two established standards for rubber ozone aging test methods, one is the static strain test method, and the other is the dynamic strain test method.
The principle of ozone corrosion
The oxidation of ozone leads to the breakdown of unsaturated organic molecules. The ozone molecule binds to the double bond of the organic molecule to generate ozonide. The spontaneous splitting of ozonide produces a carboxyl compound and a zwitterion with acidic and basic groups. The latter is unstable and can be decomposed into acids and aldehydes.
At the same time, ozone itself is not very stable and will spontaneously become oxygen and active oxygen atoms, among which the active oxygen atoms are easily combined with organic matter and cause damage.
Test procedure
Under the condition of static tensile strain, the sample is exposed to air with constant ozone concentration and constant humidity in a closed test box, and the cracking of the sample is checked for a predetermined time.
The following methods can be selected to evaluate ozone cracking under the selected ozone concentration and test temperature condition:
a) After the specified test time, check whether the sample is cracked, and if necessary, evaluate the degree of cracking of the sample;
b) Under any specified tensile strain, determine the earliest time for the sample to crack;
c) Determine the critical strain for any prescribed exposure time.
Commonly used test standards
GB7762-2003, ASTM D1149-2007, ASTM D1171-2015, ISO 10960-2017, ISO 7326-2016
