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2022/05
How To Adjust The Rubber Fixed Extension Stress?
Tensile stress and hardness are important indicators of the stiffness of rubber materials, which are the forces required to produce certain deformations in vulcanized rubber and are related to larger tensile deformations. The larger the molecular weight of the rubber, the greater the effective cross-linked tensile stress. In order to obtain the specified tensile stress, the cross-link density can be increased appropriately for rubber with a small molecular weight. Any structural factor that increases the intermolecular forces. All of them can improve the deformation resistance of vulcanized rubber. Such as CR/NBR/PU/NR etc. have higher tensile stress. Tensile stress and crosslink density have great influence. Whether it is pure rubber or reinforced vulcanizates, as the crosslinking density increases, the tensile stress and hardness also increase linearly. This is usually achieved through the adjustment of vulcanizing agents, accelerators, co-sulfurizing agents, active agents, etc. Sulfur-containing accelerators have a significant effect on the increase of tensile stress. Multi-sulfur Ken is conducive to improve the fixed tensile stress. Filler can improve the tensile stress and hardness of the product. The higher the reinforcement property and the higher the hardness, the higher the tensile stress. Tensile stress increases with the increase of hardness, the higher the increase of filling. On the contrary, the increase of softening agent, hardness decreases and the tensile stress decreases. In addition to the increase of reinforcing agent there is also the use of alkyl phenolic resin hardness up to 95 degrees, high styrene resin. The hardness of the system can reach 85 degrees with resin RS and accelerator H, etc. Tensile stress. Definition of constant tensile stress is the amount of load per unit cross-sectional area that needs to be applied to stretch a specimen to a given length. It is an indicator of rubber materials, etc. Common fixed extension stress are 100%, 200%, 300%, 500% fixed extension stress. If a specimen with a cross-sectional area of 1 square centimeter is stretched by a factor of 490N (50 kg force), then the 100% constant tensile stress is 490Pa (50 kg force/c㎡). The factors affecting the fixed extension stress are 1、The larger the molecular weight, the higher the fixed extension stress. 2、The narrower the molecular weight distribution, the lower the fixed extension stress and hardness. 3、The intermolecular force is large, the fixed tensile stress is high. 4、Standing stress and hardness increase with the increase of cross-link density. Traditional vulcanization system can obtain high tensile stress and hardness. 5、The tensile stress and hardness increase with the decrease of filler particle size, increase with the increase of structure and surface activity, and increase with the increase of filler amount. 6, fixed tensile stress and hardness with the increase in the amount of softener and reduce. 7, rubber-plastic blending can improve the tensile stress and hardness, such as NR/PE, HS blending, NBR/PVC blending, EPDM/PP blending.
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11
2022/05
Elongation At Tear Of Rubber (Elongation)
Elongation rate E (elongationpercent) Due to the deformation of the working part caused by stretching the specimen, the value of the increment of elongation and the initial length percent ratio. Constant stress elongation Eg (elongationatagivenstress) Elongation of the specimen under a given stress. Elongation at break Eb (elongationatbreak) Elongation of the specimen at break. Tearing permanent deformation (tensilesetatbreak) The specimen will be stretched to fracture, and then subjected to its state in the self-exit, recovery of a certain time (3min) after the remaining deformation, the value of the working part of the increment of elongation and the initial length percent ratio. A: tearing elongation and tensile strength related to. Only with a high tensile strength to ensure that it is not damaged during the deformation process, there will be a high elongation. Generally, with the increase of fixed tensile stress and hardness, the tearing elongation decreases, and the tearing elongation is large if the resilience is large and the permanent deformation is small. The elongation at tear is different for different rubbers. The elongation at tear of natural rubber can reach 1000% when its rubber content is above 80%. In the deformation of rubber easy to produce plastic flow will also have a higher elongation. Such as butyl rubber. B: elasticity and cross-link density related. With the increase of cross-linking density, the elasticity of vulcanized rubber increases and appears the maximum, cross-linking density continues to increase the elasticity is under the interesting trend. Manufacture of high tensile products, the degree of vulcanization should not be too high, can be slightly less sulfur or reduce the amount of vulcanizing agent. Increase the amount of filler will reduce the tearing elongation, the higher the structure of the reinforcing agent, the lower the tearing elongation, had increased the amount of softening agent, you can get a larger tearing elongation.
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23
2021/11
Rubber Bonding And Processes
Bonding agent: Also known as direct adhesive, chemical bonding or strong physical adsorption between the surfaces being bonded during vulcanization to form a firmly bonded substance. Bonding: The process of adhering two surfaces of the same or dissimilar materials together to form an interface. Adhesive: A substance that can bond adjacent surfaces of a material into one Tackifier: A substance that increases the adhesion of a vulcanized adhesive Binder: a substance that adheres discontinuous powder or fiber materials together to form a continuous whole Adhesive: the substance that connects two or more productions together, mostly in the form of sticky tape, and achieves the purpose of bonding by spraying, pasting and other processes. Bonding agent: added to the adhesive at the time of mixing, and at the time of vulcanization to make a chemical bond between the surfaces to be bonded into a strong substance adsorption, forming a strong bond Impregnating adhesive: refers to the impregnating solution containing bonding components through the impregnation process to cover the substance in the fiber fabric. Adhesion of rubber: the combination of rubber and homogeneous or heterogeneous material surfaces in contact with each other, produced by the action of van der Waals forces, hydrogen bonds, chemical bonding forces. Adhesion of rubber: The force or work required to peel off two homogeneous films by pressing them together for a short time under a small load. Phosphating: The process of placing steel parts in an acid phosphate solution to precipitate a crystalline phosphate film insoluble in water on the surface of the metal. Phosphate film P ratio: defined as P / (P + H), so the level of P ratio indicates the phosphate film in the proportion of iron di-zinc phosphate rate of high or low. Acid corrosion inhibitor: a polar molecule, selective in the active area of the metal surface in the form of adsorption of a protective film to prevent the acid and iron continue to react and achieve the purpose of corrosion inhibition. Plasma: An electrically neutral ionized gas produced by electrochemical discharges, high-energy radiation, etc., of substances under the action of an external electric field. Wetting: When the liquid and solid surface contact, the original gas-solid interface automatically replaced by the liquid-solid interface phenomenon. 1. Classification of adhesives: tackifiers, direct adhesives (bonding agents), bonding promoters, adhesives (the most widespread), and impregnating adhesives. 2. What are the varieties of cobalt salt accelerators: cobalt naphthenate, cobalt stearate, cobalt acetate, cobalt borate, cobalt decanoate. Mostly used for plating brass metal with sulfur-containing yellow glue. RFL impregnating solution is the most typical impregnating binder. r-resorcinol f-formaldehyde l-mastic. 3. the belt bundle ply, carcass, wire ring wire and carcass fiber cord in tires are related to bonding. 4. characterize the method of rubber bonding: static method (extraction method, peeling method), dynamic method (flexure method, dynamic extraction method) 5. technical methods of rubber bonding: adhesive adhesion method, adhesive method, dipping method, hard rubber method, brass plating method, direct bonding method. 6. mechanical engagement force is the main force of mechanical theory, intermolecular forces (mainly van der Waals forces) for the main role of adsorption theory. 7. In the dry situation when the rapid peeling easy to produce electrostatic gravitational force. Common bonding agents: methane-white system, triazine bonding ... , modified methacrylic .... 8. Weak interface layer at the bonding interface including: bubbles, dust, oil, precipitation of the binding agent, incomplete crystallization ....... 9. bonding forces are mainly: ① chemical bonding forces ② intermolecular forces ③ electrostatic gravitational force ④ mechanical engagement force 10. bonding transition layer formed by the thermodynamic conditions: ① bonding surface between the wettability ② bonding surface between the mutual solubility 11. The way the bonding damage: interface, body, mixing. Butyl inner tube is usually used adhesive method and direct bonding method for bonding technology. 12. dissolving medium is different, rubber adhesives are divided into solvent-based and water-based. Fiber materials are divided into natural (cotton, linen and wool) and synthetic (nylon). 13. Rubber and fiber bonding the main bonding forces are: chemical bonding force, physical adsorption, mechanical engagement force. Bonding methods: fiber impregnation method (one-step impregnation method and two-step impregnation method), fiber coating method, direct bonding method. 14. One-step impregnation method RFL impregnating solution to add modifiers ① pretreatment isocyanate ② Rp resin. 15. The role of silica in the methane-white system: catalyze the generation of methane-bonded resin, delay the sulfur yellow sulfide reaction. 16. Commonly used metal surface treatment methods include: physical mechanical method, chemical treatment method. Physical machinery: ① turning process ② sandblasting ③ ultrasonic treatment ④ mechanical polishing Chemical treatment: ① acid washing ② alkali washing ③ oxidation reduction ④ phosphate treatment 17. phosphating solution components are divided into: ① zinc phosphating ② zinc calcium phosphating ③ iron phosphating ④ manganese phosphating ⑤ composite phosphating 18. Construction method classification: ① dipping phosphating ② spray phosphating ③ brush phosphating phosphating film quality points: heavy, secondary heavy, light, secondary light. 19. According to the reaction force of oil and alkali will be divided into oil: saponifiable oil (animal and vegetable oils and fats) and unsaponifiable (① mineral oil ② petroleum jelly). 20. Degreasing with cleaning materials: organic solvents, lye. Degreasing cleaning methods: mechanical agitation, scrubbing, spray washing, electrolytic cleaning. 21. Corrosion inhibitors are: aldehyde-amine condensate, thiourea and its derivatives, pyridine and its derivatives (the best effect). 22. Detect the thickness of the phosphate film on the surface of steel parts: visual method of appearance, microstructure microscopy method. 23. phosphate film corrosion resistance commonly used detection methods are: copper sulfate drip test method, immersion method. 24. Rubber and metal bonding methods are: hard adhesive method, adhesive method, brass plating method, direct adhesion method. 25. Factors affecting the adhesion of the rubber: rubber molecular structure, rubber formula, process conditions. 1. Factors affecting the bonding effect: ① internal factors: the nature of the surface to be bonded. ② external factors: humidity and temperature of the air; process factors: temperature pressure time. Take 2 questions: to reduce the surface energy tends to stabilize, so the solid surface will produce adsorption. 2. How does adsorption on a solid surface occur? A: The solid surface layer molecules are balanced by the surrounding force field and can only capture the gas phase from the surrounding medium, the What is the effect of adsorption on bonding? A: ① conducive to bonding: to provide adsorption ② unfavorable: the surface is easy to contaminate, adsorption of dust, gas. The impact of wetting on the bonding? A: The two surfaces are moistened with each other is a necessary condition for bonding, but not the only condition. Liquid in the solid surface wetting is conducive to bonding; liquid in the solid surface is not wet, not conducive to bonding. 3. What is the impact of the surface porosity of the material to be bonded? A: ① increase the surface area and surface energy, improve the adsorption ② harbor air, reduce the contact area, bonding decreased. 4. The influence of the fluidity of the adhesive material on the skeleton material bonding? A: good fluidity, conducive to the diffusion and penetration between the two surface molecules, increase the contact area, enhance the adsorption effect, conducive to bonding. Measures to improve the fluidity: ① through plastic refining, hot refining, mixing to reduce the Menny viscosity ② extend the scorching time of the rubber ③ increase the pressure 5. What is the effect of mutual diffusion between surface molecules on bonding? A: diffusion depends on the mobility of molecular chains and compatibility, generally low viscosity, good compatibility, high temperature, high pressure, long time, the degree of diffusion, the bonding force. 6. How the chemical reaction at the bonding interface? A: ① chemical reaction between the active groups on the two surfaces ② chemical reaction between the molecules on the two surfaces through coupling agents ③ active groups obtained through surface treatment. 7. Mechanical theory of bonding methods: ① surface mechanical grinding ② surface sandblasting treatment ③ surface etching ④ immersion glue ⑤ increase the bonding pressure. 8. adsorption theory of bonding methods: ① improve the surface polarity ② surface modification ③ reduce the surface viscosity ④ surface pressure ⑤ cleaning 9. unvulcanized rubber materials are easy to bond the reason? A: ① low surface energy, weak adsorption ② good molecular mobility, conducive to diffusion and penetration ③ good wettability between surfaces, good compatibility. 10. How to improve the viscosity of unvulcanized rubber? A: ① Add plasticizer in the rubber material to improve the fluidity ② Improve plasticity through plasticizing, mixing and hot refining ③ Apply glue on the adhesive surface ④ Prevent the rubber material from spraying frost to increase the adhesion. 11. Why polyester fiber, aramid fiber and rubber is difficult to bond? A: polyester fiber molecules contain ester groups, partially shielded by the benzene ring, the surface has a small amount of -OH, -COOH, the surface has hydrophobic; aramid fiber in the amide bond mostly directly with the aromatic group, which is shielded by the aromatic group to lose activity, and the surface is smooth. 12. What are the factors affecting the bonding effect of polyester fibers and rubber? A: ① fiber surface treatment quality ② rubber formula composition ③ process conditions ④ environmental factors. How to improve the bonding effect of rubber and polyester fiber? A: ① use unsaturated rubber, polar rubber ② long scorching time ③ appropriate addition of silica ④ join the bonding system. 13. What are the reasons for the appearance of rubber or white? A: ① rubber plasticity is low, poor fluidity ② rubber spray frost or scorch ③ rubber itself poor viscosity ④ calendering speed is too fast ⑤ cloth surface temperature is low ⑥ cloth surface is not clean. 14. rubber and metal bonding between possible and difficult: ① high surface energy, strong adsorption ② surface layer can not be intermixed with the rubber, diffusion ③ there is an oxide layer, the surface has polarity ④ easy to lose electrons, electrostatic adsorption 15. metal and rubber bonding before why surface treatment? A: ① to obtain a clean surface ② improve the surface energy ③ increase the surface roughness ④ to obtain the appropriate chemical activity 16. The role of phosphating: ① enhance the bonding with the workpiece ② improve corrosion resistance ③ improve decorative ④ improve wear resistance. 17. steel parts before phosphating why degreasing? A: The grease on the parts will prevent the formation of phosphate film, and after phosphating for painting will affect the bonding force of the coating, drying properties, decorative properties and corrosion resistance. 18. phosphate solution why add accelerator? A: It is to remove hydrogen, to prevent hydrogen is adsorbed on the metal surface and thus prevent the formation of phosphate film. 19. Hard rubber formulation features: ① hardness in 82-85 ② gel rate should not be too high ③ sulfur dosage of 30-40 parts. 20. The purpose of brass plating with zinc: ① regulate the speed of rubber and brass should ② stabilize the structure of the interfacial layer, the thickness of the plating layer is 0.2um. 21. P ratio of phosphate film corrosion resistance? A: P than the high phosphate film of its crystallization is not easy to lose water, but also not easy to absorb water, good corrosion resistance.
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27
2021/10
Rubber Tensile Strength Improvement Program.
Rubber tensile strength improvement program. I. Softening system: adding softening system will reduce the tensile strength of vulcanized rubber 1. In NBR rubber, adding a small amount of softening system can improve the dispersion of carbon black, and the tensile strength may be increased. 2. In natural rubber, adding 10phr or 20phr aromatic oil, the tensile strength of vulcanized rubber decreases by 4% or 20% respectively 3. When 10phr or 20phr aromatic oil is added to SBR, the tensile strength of vulcanized rubber decreases by 20% or 30% respectively. 4. in styrene-butadiene rubber 50/butadiene rubber 50, adding 10phr or 20phr aromatic oil, the tensile strength of vulcanized rubber is basically unchanged Second, different rubber varieties have selective softeners 1. NR, IR, SBR, BR in the choice of aromatic oil, aromatic oil dosage 5 ~ 15phr 2. butyl rubber IIR, ethylene propylene rubber EPDM in the choice of paraffin oil, naphthenic oil 3. ester plasticizers (DOA, DOS, DOP, DBP) are used first in NBR, CR, Neoprene, and aromatic oils are used second. 4. petroleum resin can ensure the tensile strength of vulcanized rubber is not reduced and improve the processing performance C. Other methods to improve the tensile strength of vulcanized rubber Rubber and plastic together 1. NR, SBR/high styrene resin PS 2. NBR/PVC, NBR and polyvinyl chloride 3. NR/PE, natural rubber and polyethylene 4. EPDM/PP, ethylene propylene rubber and polypropylene 5. chemical modification of fillers, especially surface modification of white fillers 6. amine organics such as triethanolamine; polyol organics PEG series 7. metal acid esters such as zirconate esters, titanate coupling agents 8. silane coupling agent Tensile strength is to characterize the ultimate ability of the product to resist tensile damage. The main factors affecting the tensile strength of rubber are: the main valence bonds of macromolecular chains, intermolecular forces, and polymer chain flexibility. In testing rubber, the maximum tensile stress during the stretching of the specimen to fracture. Factors affecting tensile strength. 1, the tensile strength of rubber with small molecular weight increases with the increase in molecular weight. The general molecular weight of rubber between 300,000 and 350,000 tensile strength is the best. 2, the tensile strength of narrow molecular weight distribution is higher. 3, when there are polar substituents on the main chain, the tensile strength increases with the increase of intermolecular forces. For example, in nitrile rubber, acrylonitrile content increases tensile strength increases. 4, with the increase in crystallinity of rubber tensile strength increases. Such as NR, CR, CSM, IIR have higher tensile strength. 5, after the orientation of rubber molecular chain, the tensile strength in the parallel direction increases, and the tensile strength in the vertical direction decreases. 6, tensile strength decreases with the increase of cross-linked bond energy, and the peak occurs with the increase of cross-linked density. The relationship between cross-linked bond type and tensile strength decreases in the following order: ionic bond - polysulfide bond - double sulfur bond - single sulfur bond - -Carbon bond 7, carbon black particles of small and low structure (such as low structure of high wear resistance), surface oxygen groups containing more (such as slot black) its tensile strength, tear strength, elongation is high. 8, filler with small particles, large surface area, and large surface activity, then the reinforcement effect is good. As for the relationship between structure and tensile strength, the relationship between crystalline rubber with high structure is not good for tensile strength, but the opposite for non-crystalline rubber. Soft rubber carbon black dosage is generally between 40-60 parts. 9, the amount of softening agent exceeds 5 parts, it will make the tensile strength of vulcanized rubber is reduced. 10, improve the tensile strength of other methods. Such as NR/PE, HS blending, NBR/PVC blending, EPDM/PP blending, etc. A, tensile strength and the relationship between the rubber structure (1) large intermolecular forces, such as polar and rigid groups, etc. (2) molecular weight increases, Van der Waals forces increase, chain segments are not easy to slide, equivalent to the formation of physical cross-linking points between molecules, so with the increase in molecular weight, the tensile strength increases, to a certain extent to reach equilibrium. (3) The influence of the microstructure of the molecule, such as cis and trans structures. (4) crystallization and orientation Second, the relationship between tensile strength and vulcanization system (1) Cross-link density: there is a great value. (2) cross-linked bond type: with the increase of cross-linked bond energy, the tensile strength decreases; polysulfide bond has higher tensile strength, because the weak bond can play a role in releasing the stress in the stress state, reducing the degree of stress concentration, so that the cross-linked network can evenly withstand the larger stress. For NR, etc., which can produce crystallization, the early breakage of cross-linked weak bonds is also beneficial to the directional crystallization of the main chain. Third, the relationship between tensile strength and filler A large number of tests show that: the smaller the particle size, the larger the specific surface area, the greater the surface activity, the higher the structure, the better the effect of reinforcement. At the same time with the filler dosage increases, there is a maximum value, and its size is affected by the rubber species and filler type. Fourth, the relationship between tensile strength and softening agent The addition of softeners will lose tensile strength, and with the compatibility of softeners and rubber.
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27
2020/10
The 22nd International Friction And Seal Materials Technology Exchange And Product Exhibition Successfully Concluded
The 22nd International Friction and Sealing Materials Technology Exchange and Product Exhibition organized by China Friction and Sealing Materials Association was held in Hall 8 of Ningbo International Convention and Exhibition Center from October 14-16, 2020. The exhibition covered friction materials, sealing materials, raw materials for the production of friction and sealing materials, various fibers, chemical products and related machinery, attracting more than a hundred exhibitors. Earlier this year by the epidemic, resulting in the postponement of this exhibition, but the enthusiasm of enterprise exhibitors and the enthusiasm of industry experts speech, in order to make up for the impact caused by the epidemic, this organizing committee offline exhibition at the same time, but also held an online exhibition, free value-added services, through the Internet form, the exhibition to focus on a wide range of publicity, including: exhibition introduction, schedule, station recommendations, interactive zone, etc. content. The exhibition also held a series of technical presentations in the conference room of Ningbo International Convention and Exhibition Center in the same period, inviting 15 experts and industry experts to give wonderful speeches on intelligent manufacturing, the requirements of new energy vehicles for friction sealing materials, new processes of friction sealing materials, etc.
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