Identification index value of the sealing performance of several types of raw materials of rubber o-rings
The common sealing component in gate valves is rubber o-rings. Many people here have doubts about how to know the quality of the raw materials of rubber o-rings. Net weaving is here to take a look at people's rubber o-rings. What are the raw materials, and how to identify the pros and cons. Common rubber and composite materials are: natural rubber, styrene-butadiene rubber, chloroprene rubber, nitrile-butadiene rubber, ethylene-propylene rubber, butyl rubber, polyurethane material rubber, acrylic resin rubber, fluorine rubber, silica gel, etc. The main technical indicators for measuring the quality of sealing materials: 1. Tensile properties Tensile properties are the first properties to be considered for sealing materials, including: tensile strength, tensile stress, elongation at break and permanent breakage shape variable. The tensile strength is the greater in-situ stress of the specimen from stretching to rupture. In-situ stress at constant elongation (strain rate at constant elongation) is the in-situ stress achieved at the required length. Elongation is the deformation of the specimen when it is subjected to the required tensile force, and the ratio of the increase or decrease of the length to the original length is Elongation at break is the elongation of the specimen at break. The tear-off permanent deformation is the residual deformation in the middle of the road marking after the tensile rupture of the specimen. 2. Strength Strength expresses the ability of the sealing material to resist the intrusion of external force, and it is one of the basic properties of the sealing material. The strength of the raw material is related to other properties to a certain level. The higher the strength, the greater the compressive strength, the smaller the elongation, the higher the wear resistance, and the worse the cold resistance. 3. Shrinkage performance Rubber products are generally in the state of shrinkage. Because of the viscous ductility of elastomer materials, the working pressure will decrease with time when shrinking, which is mainly manifested in shrinkage stress relaxation; after removing the working pressure, it cannot respond to the original shape, mainly Manifested as shrinking permanent deformation. This situation is more pronounced in high temperature and raw oil substances, and this performance is related to the tolerance of the sealing workability of the sealing craft. 4. The ultra-low temperature performance is used to consider the index value of the ultra-low temperature characteristics of rubber products. The following two methods for detecting ultra-low temperature performance are introduced in detail: 1) Ultra-low temperature shrinkage temperature: stretch the sealing material to a certain length, then fix it, and quickly cool it with water to The freezing and cleaning temperature is as follows. After achieving equilibrium, let go of the test piece and raise the temperature at a certain rate. Record the temperature when the style shrinks by 10%, 30%, 50% and 70%, respectively, expressed as TR10, TR30, TR50, and TR70. The raw material specification uses TR10 as the index value, which is related to the brittle fracture temperature of the rubber. Ultra-low temperature flexibility: After the test piece is refrigerated at the required ultra-low temperature for the required time, it is bent back and forth according to the specified angle of view, and the sealing performance of the hydraulic seal after the continuous effect of the dynamic load at the ultra-low temperature is investigated. . Rubber O-ring 5. Acid and alkali resistance or substance resistance In addition to contact with crude oil, diesters, and silicate oils, the sealing material sometimes also touches corrosive substances such as acid and alkali in chemical industry. In addition to being corroded in this substance, it will also cause swelling and compressive strength to decrease at high temperature, and the strength will decrease; in addition, the flame retardant and soluble chemical substances in the sealing material are drawn out, resulting in quality relief, The volume becomes smaller, causing leakage. Generally, at a certain temperature, after soaking in the material for a number of times, the quality, volume, compressive strength, elongation, and strength changes are measured to identify the acid and alkali resistance or material resistance of the sealing material. 6. Anti-aging performance The performance of the sealing material is affected by the effects of oxygen cylinders, three oxygen, heat, light, moisture, and mechanical equipment, which is called embrittlement of the sealing material. Aging resistance (also known as aging resistance) can be expressed by the change in compressive strength, elongation, and strength of the embrittled style. The smaller the change rate, the higher the aging resistance. Note: Aging resistance refers to a series of embrittlement conditions such as discoloration, discoloration, cracking, delamination and reduction in compressive strength of plastic products due to external standards such as sunlight exposure, temperature change, and sun and rain. .In which direct ultraviolet light is the primary condition to promote plastic embrittlement.