Factors Affecting Compression Permanent Deformation Of Vulcanized Rubber
Compression permanent deformation is one of the important performance indexes of rubber products. The size of compression permanent deformation of vulcanized rubber relates to the elasticity and recovery of vulcanized rubber. Some people tend to think that the elasticity of rubber is good and their recovery is fast and permanent deformation is small. This understanding is not enough. Resilience and recovery are two interrelated nature. But sometimes the nature of rubber has not changed fundamentally. The magnitude of permanent deformation is mainly controlled by the change of rubber resilience. The factors that influence recovery ability include molecular force, viscosity, network structure change and destruction, and molecular shift. When the deformation of rubber is caused by the elongation of molecular chains, the recovery (or the size of permanent deformation) is determined mainly by the elasticity of rubber. If the deformation of rubber is accompanied by the destruction of the network and the flow of the molecular chain, this part can be said to be unrecoverable, and it has nothing to do with elasticity. Therefore, all factors that affect rubber elasticity and recovery are the factors that affect the compression permanent deformation of vulcanized rubber.
There are several concepts, such as elasticity, resilience, resilience, elasticity and modulus, compression permanent deformation, and permanent deformation. The relationship between them is not easy to express clearly.
Elasticity -- the elasticity of rubber should be a concept in Hun theory, which indicates the difficulty of rotation of rubber molecular segments and the lateral base, or the size of the molecular chain and molecular interaction force of rubber molecules. The elasticity of vulcanized rubber is also related to the density and regularity of crosslinking network.
Elasticity and breaking of permanent deformation -- we often say that natural rubber has good elasticity, but its permanent deformation is often very large. This is mainly due to the large secondary growth rate of natural rubber, the destruction of network and the large displacement of molecular chains in the secondary growth process, and the long and inresumable part of the recovery process after fracture. Permanent deformation of natural rubber is not necessarily great if the permanent deformation of fixed length is compared.
Resilience or resilience is measured under fixed load (or fixed energy) conditions. The size of elasticity is directly related to the degree of crosslinking or modulus of vulcanizate, which is the synthesis of rubber elasticity and viscosity (or absorption).
Compression permanent deformation is measured under fixed deformation conditions, and its value is related to elasticity and resilience of rubber. Now let's talk about rubber elasticity and recovery.
Elasticity of rubber
1. types of rubber
Elasticity depends on the difficulty of internal rotation of molecular chains, and the magnitude of molecular force. Such as natural rubber, butadiene rubber, butyl rubber, silicone rubber and so on are considered to have good elasticity.
2. molecular weight
It affects the degree of curl and the number of useless ends. The molecular weight is large and the elasticity is good.
3. chemical composition and structure of copolymer rubber
The elasticity of Ding Benjiao and NBR increased with the increase of styrene and acrylonitrile content. In ethylene propylene rubber, the amount of propylene in 4O to 5O% is the best, when the copolymer is a random copolymer. If the ethylene content exceeds 7O%, the long ethylene block is formed, and the long ethylene block is easy to form the knot and causes Yi Bingjiao to lose its elasticity.
Two. Effect of reinforcing filler on elasticity of vulcanizate
Non carbon black reinforcing filler can damage the elasticity of rubber and increase compression permanent deformation. This is related to the slippage of rubber molecules on the surface of inactive filler under stress and the removal of stress, which hinders the recovery of molecular bonds. The application of coupling agent can greatly improve the effect of non reinforcing filler on the elasticity of vulcanizates (improving the separation and surface activity of filling). In most literatures, the elasticity of vulcanizates increases with the increase of particle size of carbon black, but the influence of filling amount on the elasticity of vulcanizates is often neglected. As a matter of fact, all kinds of rubber products have certain hardness and strength requirements. For example, the consumption of single reinforcing carbon black should be increased, which will also damage the elasticity and recovery of rubber. In a certain amount of vulcanized rubber, the deformation of the filled rubber molecular chain is larger than that of the actual deformation, and the expansion value is proportional to the filling amount. The increase of deformation will also affect the displacement and recovery of the rubber molecular chain and increase the permanent deformation. Using suitable reinforcing agent and proper mixing process, the ideal structure form of the rubber compound can be obtained and high elastic vulcanized rubber can be obtained.
Three, soften Jing and plasticized Jing
Softening Jing is usually a good kind of gum or resin that is compatible with rubber tallow, and it can be used as a good oil or resin for Vitex and rubber tallow. They can not only increase the elasticity of rubber, but also increase the molecular chain flexibility and increase the mobility of molecular chains. However, these two effects can be adjusted by softening agent, reasonable dosage and application of plasticizer, and proper processing technology, so as to obtain a good vulcanized rubber. On some occasions, it can play a special role.
Four. Crosslinking degree of vulcanized rubber and structure of vulcanizate
Effect of compression on permanent change
1. effect of crosslinking degree
When the molecular chain of rubber is under the stress, it will cause the displacement of the molecular chain to produce stress relaxation. Some cases can even relax to zero. When the stress is removed, the recovery ability of the rubber molecules will be reduced or even lost, resulting in permanent deformation. Higher crosslinking degree can reduce displacement and stress relaxation of rubber molecules, maintain higher recovery ability and reduce compression permanent deformation.
2. effect of sulphidation
The compression permanent deformation of vulcanized rubber is usually carried out at a higher temperature. After vulcanization, the deformed rubber molecules are bound by the newly formed cross-linking bonds. The removal of the rubber molecules after stress removal is hindered, resulting in greater permanent deformation. This post crosslinking action is different from the degree of crosslinking mentioned in point L.
3. crosslinking structure and chemical stress relaxation
The oxidation of polysulfide crosslinking bonds at high temperature and long time leads to the breakage of cross-linked bonds, resulting in chemical stress relaxation and molecular chain displacement. The broken cross-linked bonds form new crosslinks in unstressed places. The increase in compressive deformation caused by chemical stress relaxation is due to the double effect of molecular chain shift and molecular chain recovery. The solution is to change the cross-linking structure and enhance the antioxidant effect.
Five, low temperature compression permanent deformation (cold resistance coefficient)
The impact of low temperature compression permanent deformation of vulcanized rubber is still elasticity and recovery. The form of expression is the bond and vitrification of the rubber molecular chain, and the solutions are as follows: first, reduce the glass pition temperature of the rubber; two, the quality of the broken rubber. For different rubber varieties, the measures adopted are quite different. For example, natural rubber, which is easy to produce, can be modified or modified at high temperature to produce a certain amount of p structure and destroy its low temperature properties. For neoprene and ethylene propylene rubber, it is necessary to select varieties that are difficult to knot and apply cold resistant plasticizers to reduce the glass pition temperature. The cold resistance plasticizer is mainly used to reduce the vitrification temperature of Ding Fu rubber. Sometimes some unconventional methods may be adopted to achieve the goal.
- Related reading
Improving Dyeing Properties Of Synthetic Microfiber Leather With Suitable Dyes
|- City Express | Jiangnan International Silk City Fabric Area Grand Opening And 2020 China Silk Clothing New Trend Of Fashion Appraisal
- Instant news | 1 Million 500 Thousand Yuan! This Overseas Chinese Enterprise Donated Cash To The Zhejiang Provincial Samaritan Foundation.
- Expo News | 2019 The Third China Customized Economic Summit (Expo) Will Be Held In Beijing.
- Show show | Hunan Fashion Fair, Su Bai Is The Champion.
- News Republic | In Order To Ensure The Quality Of Ready To Wear Clothes, The Children Of The Time Box Are Escorted By Many Links.
- Footwear industry dynamics | New York Brand Steve Madden Launches Brand New Shoes, Naked Copy?
- Fashion shoes | Nike Air Tailwind 79 Shoes Orange Orange New Color Comes Out, Retro OG Fan
- Bullshit | Herschel Supply 2019 New Winter Luggage Series On Sale
- Market trend | Crude Oil Explosion In Iran Oil Tanker Is Expected To Skyrocket. Chemical Fiber Raw Materials Will Probably Increase.
- Fashion shoes | Grey Nike Air Force 1 Must Not Be Missed!
- Improving Dyeing Properties Of Synthetic Microfiber Leather With Suitable Dyes
- Analysis Of Causes For Dissatisfaction Of Injection Molded Products
- Formulation Of New Neoprene Adhesive
- Common Problems In Injection Molding After Adding Color Masterbatch
- Matters Needing Attention In The Use Of Adhesive Products
- Main Functions Of Rapid Prototyping Technology
- Process Characteristics Of Thermosetting And Thermoplastic Reinforced Plastics
- Process For Reducing Pollution In Tanning Process
- Combination Of Shoe Sole Raw Materials
- Women Are Not As Good As Men Because Wages Are Unreasonable.