A. definition of rubber

 Popular definition: rubber is a kind of high-elasticity polymer compound (molecular weight is generally over 100,000), so it has high elasticity not found in other materials.  Therefore, it is also called elastic body.  Origin of rubber: made by drying and solidifying the latex of tropical American natural weeping tree.  Development: Invention of Vulcanization Method.  Vulcanization is a chemical change process in which linear macromolecular chains of rubber form a three-dimensional network structure through chemical cross-linking.

 B. brief introduction of rubber classification

 Rubber is classified by material source: natural rubber and synthetic rubber.  According to performance and usage: general rubber and special rubber.

 First, natural rubber, as its name implies, is made from natural or artificially planted rubber trees by tapping, filtering and cleaning.  Drying and other processes.  91% ~ 94% of its components are rubber hydrocarbons, and the rest are non-rubber substances such as protein, fatty acid, ash, sugar, etc.

 Second, synthetic rubber is a polymer formed by polymerizing petroleum and natural gas as raw materials and diolefins and olefins as monomers.

 3. Universal rubber: Any rubber that has the same or similar properties as natural rubber and has better physical and processing properties and can be widely used in tires and other general rubber products is called universal rubber.  Common rubbers include natural rubber (NR), styrene butadiene rubber (SBR), nitrile butadiene rubber (NBR), cis-polybutadiene rubber (polybutadiene rubber, BR), isoprene rubber (polyisoprene rubber, IR), neoprene rubber (CR), ethylene propylene rubber (EPR), butyl rubber (IIR).  1. Isoprene (IR) Isoprene is a monomer.  Because the structure is the same as NR, it is also called artificial natural rubber.  The properties are similar to NR.  2. Butadiene rubber (BR) butadiene has the best elasticity and low temperature resistance among general purpose rubbers, and is used for modification of tires, wear-resistant products, cold-resistant products, shockproof products and plastics, etc.  Due to processing difficulties, it is usually combined with NR and SBR.  3. Chloroprene rubber (CR) chloroprene is used as the main raw material and is formed by homopolymerization or copolymerization of a small amount of other monomers.  It is a synthetic rubber with a balance of physical property, drug resistance, heat resistance, weather resistance, low combustion and oil resistance, but it has poor electrical insulation performance and cold resistance, and the raw rubber is unstable during storage.  It is mainly applied to adhesives, conveyor belts, oil-resistant rubber tubes and gaskets, etc.  4. butyl rubber (IIR) isobutylene/isoprene copolymer.  It is characterized by extremely low air permeability.  It has excellent polar solvent resistance, heat resistance and drug resistance, but has poor processability, difficult vulcanization, and is not easy to mix NR, SBR and other rubbers.  5. NBR) 6. SBR) 7. EPDM

 4. Special Rubber: Any rubber product with special properties that is specially used for special properties such as heat resistance, cold resistance, chemical corrosion resistance, oil resistance, solvent resistance and radiation resistance is called special rubber.  Special rubbers include: silicone rubber (Q), fluororubber (FPM), polyurethane rubber (AU/EU), polysulfide rubber (TR), polyacrylate rubber (ACM/AEM), epichlorohydrin rubber (ECO), chlorinated polyethylene rubber (CPE), chlorosulfonated polyethylene (CSM), butyl rubber (PBR), etc.

 C. formula structure of rubber compound

 The formula structure of rubber compound is raw rubber: also called raw rubber, and no other ingredients are added.  Vulcanizing agent: chemical substance that can vulcanize (crosslink) rubber.  Such as sulfur, peroxide, etc.  Accelerator: Chemical substance that can shorten curing time, reduce curing temperature, reduce dosage of vulcanizing agent, and improve and improve mechanical properties and chemical stability of vulcanized rubber.  Such as TT, CZ, etc.  Active agent: chemical substance that can increase the activity of accelerant, improve vulcanization speed and vulcanization efficiency, and improve the performance of vulcanizate.  Such as ZnO, etc.  Reinforcing agent: it can improve the mechanical properties of rubber, such as tensile strength, abrasion resistance, tear strength and constant tensile stress, thus achieving the functions of improving service performance and prolonging service life.  Such as carbon black, white carbon black.  Plasticizer: also called softener, used to reduce the hardness of rubber.  Most of them are oils, such as DOP, epoxidized soybean oil, paraffin oil, etc.  Anti-aging agent: substances that enhance rubber's resistance to destruction by light, heat, oxygen, ozone, ultraviolet rays, such as 4010-NA, RD, etc.  Anti-scorching agent: a substance that can prevent or delay the occurrence of early vulcanization (scorching) during the processing and storage of rubber before vulcanization when added to rubber in a small amount.  Others: such as colorants, dispersants, antistatic agents, flame retardants, foaming agents, tackifiers, etc.

 D, commonly used rubber types, properties and uses

 Commonly used rubber types 1. natural rubber (NR) 2. styrene butadiene rubber (SBR) 3. nitrile butadiene rubber (NBR) 4. ethylene propylene rubber (EPR) 5. silicone rubber (q)

 1. Characteristics and chemical properties of natural rubber: natural rubber is unsaturated rubber, which is easy to undergo vulcanization reaction with vulcanizing agent, oxidation and cracking reaction with oxygen and ozone, chlorination and bromination reaction with halogen, cyclization reaction under the action of catalyst and acid, etc.  Physical and mechanical properties: It has good elasticity at normal temperature, and the elongation rate can reach up to 1000%.  In the range of 0~100℃, the resilience can reach more than 50~85%.  Thermal Properties: Softens slowly after heating, starts to flow at 130~140℃, starts to decompose at 200℃, and decomposes violently at 270℃.  Hardened during storage, easy to crystallize at low temperature and brittle at-70℃.  Medium resistance: medium refers to oils, liquid chemicals, etc.  Natural rubber is nonpolar, soluble in nonpolar solvent and nonpolar oil, insoluble in cyclohexane, gasoline, benzene and other media, insoluble in polar acetone, ethanol and the like, insoluble in water, resistant to 10% hydrofluoric acid, 30% sulfuric acid,