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Advantages and application of butyl rubber

Release time:2020-12-16

1. The benefits of butyl rubber

  1. Air permeability

  The air permeability of butyl rubber is the lowest among hydrocarbon rubbers. The gas solubility of butyl rubber is close to that of other hydrocarbon rubbers, but its gas loosening speed is much lower than other rubbers. This is one of the most important basic functions of butyl rubber, and it determines the main uses of butyl rubber in several aspects such as inner tubes and inner liners.

  At 40℃, the air permeability coefficient of butyl rubber Q = 0.6×103, which is about 1/20 of natural rubber, 1/76 of butadiene rubber, 1/8 of styrene butadiene rubber, and 1/ of ethylene propylene rubber. 13. As the temperature progresses, the difference in air permeability gradually decreases. However, the difference is still large even at higher temperatures.

  Generally speaking, the type and degree of vulcanization of butyl rubber have little effect on air permeability, but the amount of operating oil and filler has a great impact on air permeability. For example, under the condition of filling 50 parts of carbon black, When the operating oil is increased from 0 to 30 parts, the air permeability increases 3 times. Increasing the amount of carbon black reduces the air permeability. Using flake fillers (such as mica), air permeability can be greatly reduced.

  2. Heat resistance

  The low chemical unsaturation of butyl rubber, coupled with the inactivity of the polyisobutylene chain, makes the heat and oxidation resistance of butyl rubber far superior to other general rubbers. The heat-resistant rubber formula is selected. After the vulcanized rubber is aged by 120℃×144h hot air, the elongation is not changed much, and the tensile strength can still be maintained above 70%. Using resin-vulcanized butyl vulcanizate, after aging at 170℃×144h, the tensile function is only reduced by about half, and its maximum operating temperature (short time) can reach 200℃.

  Butyl rubber has excellent heat aging function. Thermal oxidative aging of vulcanizates is degradable, and aging tends to soften.

  3. Weather resistance

  Carbon black reinforced butyl vulcanizate has excellent weather resistance and can be exposed to sunlight and oxygen for a long time without damage. The speed, depth and extent of surface degradation of butyl rubber are affected by the light reflection and oxygen absorption of the filler, as well as the nature and amount of the filler. The butyl vulcanization with highly reflective fillers (such as titanium dioxide and zinc oxide) Glue has better weather resistance.

  4. Anti-ozone function

  Compared with highly unsaturated rubber, butyl rubber has particularly good ozone resistance. Typical butyl vulcanized rubber has an ozone resistance about 10 times higher than that of highly unsaturated natural rubber and styrene butadiene rubber.

  Under given strain conditions, butyl rubber has fewer cracks after outdoor exposure, and the increase rate is relatively slow. The anti-ozone function of butyl rubber is related to the degree of unsaturation and vulcanization of the rubber. The anti-cracking function decreases as the degree of unsaturation increases, and progresses with the extension of the vulcanization time (especially under low vulcanization conditions). Carbon black and process oil also have an impact on the anti-ozone function of butyl rubber. As the amount of carbon black increases, the anti-cracking function of the vulcanized rubber is improved (under the same vulcanization condition), but the condition of filling a very high amount of carbon black is not. Hydrocarbon plasticizers will reduce the anti-ozone function and increase the rate of increase in cracking.

  In short, for the ozone resistance of traveling butyl rubber products, the following methods can be used: ①The degree of vulcanization should be deep; ②The unsaturation of rubber should be low; ③Plasticizers and coarse-particle non-carbon black fillers are not suitable for many fillings; ④The protective agent should be used properly; ⑤The compound should be loose and evenly moisturized.

   5. Resistant to acids, alkalis and polar solvents

  Butyl rubber is particularly resistant to animal and vegetable oils, and swells very little in a variety of polar organic media such as alcohol and acetic acid. The swelling degree decreases with the progress of the vulcanization degree and the increase in the amount of filler, especially carbon black. Butyl rubber is not resistant to concentrated oxidizing acids (such as HNO3, H2SO4), but resistant to non-oxidizing acids and oxidizing acids with dilute to moderate concentrations, alkali-resistant solutions and oxidation-recovery solutions. However, it swells severely in aliphatic solvents. When planning acid and alkali-resistant rubber formulations, it is necessary to consider the corrosion of fillers by the medium. For example, when planning liquid acid-resistant rubbers, calcium carbonate should not be used as a filler.

  6. Electric function

  The electrical insulation and corona resistance of butyl rubber are better than those of general rubber. The volume resistance can reach 1016Ω·cm or more, which is 10~100 times higher than general rubber. The betweenness 1kHz is 2~3 and the power factor (100Hz) 0.0026.

  7. Water absorption

  The water penetration rate of butyl rubber is extremely low, and it has excellent water resistance at normal temperature. The water absorption rate at normal temperature is 10-15 times lower than other rubbers. This excellent function of butyl rubber is an important contribution to electrical insulating compounds. The butyl vulcanizate reinforced with carbon black and vulcanized with resin can achieve low water absorption under high temperature and long time exposure conditions. In order to keep the butyl rubber compound exposed to water or high temperature for a long time, the following considerations should be taken in principle:

  a. Filler should be hydrophilic and meta-electrolyte;

  b. The water-soluble matter in the vulcanization system should be as small as possible;

  C. The selected reinforcing filler and curing conditions should make the vulcanized rubber have high elastic modulus and other physical functions.

  8. Damping function Butyl rubber has excellent damping function in the temperature range of -30~50℃, and still has flexibility at the glass transition temperature (-73℃). It is used for shock absorption or shock isolation, which can quickly attenuate the safety oscillation. It is especially suitable for applications that require high buffering functions such as engine mounts and shock absorbers.

  2. Introduction of Butyl Rubber Market and Skills

  The global butyl rubber, especially halogenated butyl rubber, is operated by ExxonMobil and ARLANXEO for its skills and market base. The production capacity concentration of the two is as high as 80%, which brings high profits to it. .

  The start of nitrile rubber in my country

  my country started late in the field of butyl rubber production, and its technical strength is relatively weak. The research and development of laboratory skills for butyl rubber in my country began in the 1960s. It was once dominated by the Lanzhou Institute of Chemical Industry. More than 300 people from 20 units have participated in research, research and development operations, and laboratory pilot tests have also been established. Equipment, obtained certain skill results. However, due to the influence of many factors, our country stopped the skill development work in 1983 and turned to seek a way to introduce skills to produce industrial equipment.

  3. Development of my country's butyl rubber skills

  my country has always attached importance to the development of the skills that constitute the rubber industry. In 2017, the Ministry of Science and Technology included the key skills of high-function rubber industrialization in the national key research and development program, aiming to break the technical bottleneck of the entire industrial chain of rubber, tires and other high-end rubber products .

  At the beginning of December 2018, this national key development project completed severe technical breakthroughs in central technical areas such as star-branched butyl/bromobutyl rubber composition and double-B tire preparation skills. The project team broke the slurry method butyl rubber polymerization skills, selected anionic polymerization skills and theories, prepared a series of branching agents with slurry stabilization function for cationic butyl rubber polymerization, and announced a complete set of slurry method star branching Butyl rubber preparation skills. In addition, scientific researchers have announced a new reaction process for manipulating bromine substitution sites and advancing bromine utilization, increasing the secondary bromine selectivity of bromobutyl rubber from 84.2% to 97%.

  In addition, according to the structural characteristics of star-shaped branched butyl rubber products, the project team made innovations in processing theory, and developed a vulcanization bladder formula for star-shaped branched butyl rubber that is resistant to high temperatures and flexing to make it evenly serviceable. Travel more than 15%.

  In positive ion polymerization, it is generally necessary to carry out at extremely low temperature to reduce side reactions, and to form a relatively high molecular weight polymer. For example, a high molecular weight butyl rubber generally needs to be carried out at -100°C. Isobutylene and a small amount of isoprene produce positive ion copolymerization. The Wu Yixian research team introduced specific structural compounds to adjust the ionicity and steric hindrance of the active center and regulate the polymerization kinetics. After the polymerization is completed at -60℃, it can be prepared. The traditional system needs to be polymerized at -100℃. For the obtained isobutylene polymer with high molecular weight, the temperature difference of 40°C will bring significant energy saving and consumption reduction effects.

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