Who has the answers to making glass strips and comparing them with other raw materials in production?

There are many materials in rubber strip, such as silicone rubber (methyl, ethylene), neoprene (neoprene, diene) and ethylene propylene diene (terpolymer of ethylene, propylene and diene).

Silicone rubber Chengdu senfa rubber & plastic co., ltd

Room temperature vulcanized NBR silicone rubber is poly-β-nitrile ethyl methyl siloxane. Room temperature vulcanized silicone rubber not only has the light resistance, ozone resistance, moisture resistance, high and low temperature resistance and excellent electrical insulation performance of silicone rubber, but also has good oil resistance to nonpolar solvents such as aliphatic and aromatic solvents, and the oil resistance is close to that of ordinary oil-resistant nitrile rubber, so it can be used as sealing and potting material for oil-contaminated parts and oil-resistant electronic components.

(5) room temperature vulcanized fluorosilicone rubber

Room temperature vulcanized fluorosilicone rubber is poly-γ-trifluoropropyl methyl siloxane. Its main characteristics are fuel resistance, solvent resistance, high temperature degradation resistance and good extrusion performance. Mainly used for sealing and caulking the integral fuel tank of supersonic aircraft, bonding and fixing fluorosilicone rubber gaskets and washers; Adhesion of silicone rubber and fluorosilicone rubber, and fuel resistance in chemical engineering and general industry; Adhesion of solvent-resistant parts.

(6) room temperature vulcanized styrene silicone rubber

Room temperature vulcanized phenylene silicone rubber is a kind of silylene (biphenyl) siloxane polymer, and its outstanding advantage is its excellent high-energy radiation resistance. Experiments show that rubber can still keep its elasticity after being irradiated by 1x 109 roentgen gamma rays or 1x 10 18 neutrons /cm2, which is larger than room temperature vulcanized methyl silicone rubber 10 ~ 15.

Room temperature vulcanized styrene silicone rubber can be used as high temperature and radiation resistant adhesive sealing material and insulating protective layer for motors in atomic energy industry, nuclear power plants and aerospace fields. Www.slicom.cn Chengdu Senfa Rubber & Plastic Co., Ltd.

Room temperature vulcanized silicone rubber (RTV) is a new type of silicone elastomer that came out in 1960s. The most remarkable feature of this rubber is that it can be cured in situ at room temperature without heating or pressure, and it is very convenient to use. So it became an important part of silicone products as soon as it came out. At present, room temperature vulcanized silicone rubber has been widely used as adhesives, sealants, protective coatings, potting and molding materials, and has its uses in all walks of life.

Room temperature vulcanized silicone rubber is called liquid silicone rubber because of its small molecular weight. Its physical form is usually flowable fluid or viscous paste, and its viscosity is between 100 ~ 1000000 centistoke. According to the use requirements, the rubber mixture before vulcanization can be made into self-leveling castable or putty that does not flow but can be scraped. The filler used in room temperature vulcanized silicone rubber is similar to that used in high temperature vulcanized silicone rubber, and silica is used as reinforcement, so that the fracture strength of vulcanized rubber reaches 10 ~ 60 kg/cm2. Adding different additives can make the compound have different specific gravity, hardness, strength, fluidity and thixotropy, and make vulcanized rubber have various special properties such as flame retardant, electrical conductivity, thermal conductivity and ablation resistance.

Room temperature vulcanized silicone rubber can be divided into one-component and two-component room temperature vulcanized silicone rubber according to its packaging mode, and can be divided into condensation type and addition type according to vulcanization mechanism. Therefore, RTV silicone rubber can be divided into three types according to composition, vulcanization mechanism and application process, namely, one-component RTV silicone rubber, two-component condensed RTV silicone rubber and two-component addition RTV silicone rubber.

The raw rubber of one-component and two-component condensation type room temperature vulcanized silicone rubber is α, ω-dihydroxy polysiloxane; Addition room temperature vulcanized silicone rubber is a polysiloxane containing alkenyl and hydrogen side groups (or end groups). Because it can achieve good curing effect at a temperature slightly higher than room temperature (50 ~ 150℃), it is also called low temperature vulcanized silicone rubber (LTV).

These three series of RTV silicone rubber have their own advantages and disadvantages: one-component RTV silicone rubber has the advantage of convenient use, but the deep vulcanization speed is difficult; Two-component RTV silicone rubber has the advantages of no heat release, small shrinkage, no expansion and no internal stress during curing, and can be cured at the same time on the inner surface and deeply vulcanized; The curing time of addition room temperature vulcanized silicone rubber mainly depends on the temperature, so the curing speed can be controlled by adjusting the temperature.

One-component room temperature vulcanized silicone rubber www.sen88.cn

The vulcanization reaction of one-component room temperature vulcanized silicone rubber is initiated by moisture in the air. The commonly used crosslinking agent is methyl triacetoxysilane, whose Si-O-C bond is easy to hydrolyze, and the acetoxy group combines with the hydrogen group in water to form acetic acid, and the hydroxyl group in water moves to the original acetoxy position to form trihydroxymethyl silane. Trihydroxymethyl silane is extremely unstable, and it is easy to condense with linear silicone with hydroxyl group to form cross-linked structure. Usually, raw silicone rubber containing silanol end groups, fillers, catalysts, cross-linking agents and other compounding agents are put into a sealed hose, and when in use, they are extruded from the container, vulcanized into elastomers with the help of moisture in the air, and at the same time, low molecular weight substances are released.

Besides methyltriacetoxy silane, the crosslinking agent can also be silane containing alkoxy group, oxime group, amine group, amide group and ketone group. The dealcoholized one-component RTV silicone rubber releases alcohol after crosslinking with alkoxy group, and generates oxime after crosslinking with oxime group, which is called deoximated RTV silicone rubber. Therefore, with different crosslinking agents, one-component RTV silicone rubber can be deacidified, deoximated, dealcoholized, deaminated, deamidated and ketonized, but deacidified silicone rubber is the most widely used one at present.

The curing time of one-component room temperature vulcanized silicone rubber depends on curing system, temperature, humidity and the thickness of silicone rubber layer. Increasing the temperature and humidity of the environment can accelerate the curing process. Under typical environmental conditions, after 15 ~ 30 minutes, the surface of silicone rubber will not stick, and the 0.3 cm thick adhesive layer can be cured within one day. The curing depth and strength will gradually increase in about three weeks.

One-component RTV silicone rubber has excellent electrical properties and chemical inertness, as well as heat resistance, natural aging resistance, flame retardancy, moisture resistance and air permeability. They can keep elasticity for a long time in the range of -60 ~ 200℃. It does not absorb heat or release heat during curing, and has small shrinkage after curing and good adhesion to materials. Therefore, it is mainly used as adhesive and sealant, and other applications include in-situ forming gasket, protective coating and caulking material. Many formulations of one-component silicone rubber adhesive show self-adhesive properties for many materials, such as most metals, glasses, ceramics and coagulants. For example, for bare aluminum, the shear strength can reach 200 lbs/cm2 and the tear strength can reach 20 lbs/cm2 (0.35 Joule/cm2). When bonding is difficult, primer can be applied to the substrate to improve the bonding strength. Primers can be reactive silane monomers or resins, and when they are cured on the substrate, a modified surface suitable for siloxane bonding is produced.

One-component room temperature vulcanized silicone rubber is easy to use, but its vulcanization depends on the moisture in inert atmosphere, which limits the thickness of vulcanized rubber and can only be used in occasions with a thickness less than 6 mm

The vulcanization reaction of one-component room temperature vulcanized silicone rubber is gradually carried out from the surface to the inside, and the thicker the adhesive layer, the slower the curing. When the deep part needs rapid vulcanization, the method of layered pouring and gradual vulcanization can be adopted, and some mixed rubber can be added each time, and then the material can be replenished after vulcanization, so that the total vulcanization time can be reduced. Adding magnesium oxide can accelerate the vulcanization of deep glue.

chloroprene rubber

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(Synthetic polymer compound) is made of chloroprene as the main raw material by homopolymerization or polymerization of a small amount of other monomers. For example, it has high tensile strength, excellent heat resistance, light resistance and aging resistance, and oil resistance is better than natural rubber, styrene-butadiene rubber and cis-butadiene rubber. It has strong flame retardancy and excellent flame retardancy, high chemical stability and good water resistance. The disadvantages of chloroprene rubber are poor electrical insulation and cold resistance, and the raw rubber is unstable during storage. Neoprene rubber has a wide range of uses, such as making covering materials for transportation belts and transmission belts, wires and cables, making oil-resistant hoses, gaskets and chemical-resistant equipment linings.

Neoprene rubber is made by emulsion polymerization of 2- chloro-1 3 butadiene, which can be modified by sulfur and 2,3-dichloro-1 3 butadiene (ACR).

Neoprene rubber can be used in different technical fields, mainly in rubber industry (6 1%). However, as a raw material of adhesive, it is also very important and has different uses (6%), such as impregnated products (such as gloves), molded foam materials, asphalt modification and so on.

Widely used in the field of elastomers, such as molded products, cables, transmission belts, conveyor belts, profiles and so on.

Neoprene rubber has no outstanding performance, but its comprehensive performance is unique among synthetic rubber. It has:

* Excellent mechanical strength

* High ozone and weather resistance.

* Good anti-aging performance

* Low flammability

* Good chemical resistance

* Moderate oil resistance and flame retardancy

* can be adhered to a variety of substrates.

By using different catalytic systems, chloroprene rubber can be vulcanized in a wide temperature range.

EPDM rubber Chinese name: EPDM rubber

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Brief introduction of EPDM

EPDM is a terpolymer of ethylene, propylene and unconjugated diene, which has been commercialized in 1963. The annual consumption in the world is 800,000 tons. The main characteristics of EPDM are its superior oxidation resistance, ozone resistance and erosion resistance. Because EPDM belongs to polyolefin family, it has excellent vulcanization characteristics. Among all rubbers, EPDM has the lowest proportion. It can absorb a lot of filler and oil without affecting its characteristics. Therefore, a low-cost rubber mixture can be produced.

Molecular structure and characteristics

EPDM is a terpolymer of ethylene, propylene and unconjugated diene. Dienes have a special structure, and only one of the two bonds can be polymerized. Unsaturated double bonds are mainly used as crosslinking agents. The other unsaturated one will not become the main chain of the polymer, but only the side chain. The main polymer chain of EPDM is completely saturated. This characteristic makes EPDM resistant to heat, light, oxygen and especially ozone. EPDM is essentially nonpolar, resistant to polar solutions and chemicals, with low water absorption and good insulation characteristics.

In the production process of EPDM, its characteristics can be adjusted by changing the number of three monomers, ethylene-propylene ratio, molecular weight and its distribution and vulcanization mode.

Selection of the third monomer of EPDM

The third and second olefin monomers are polymerized by ethylene and propylene, resulting in unsaturation in the polymer, thus realizing vulcanization. The selection of the third monomer must meet the following requirements:

There are at most two bonds: one is polymerizable and the other is vulcanizable.

The reaction is similar to two basic monomers.

Random aggregation of primary keys produces a uniform distribution.

Sufficient volatility, easy to remove from the polymer.

The curing speed of the final polymer is suitable.

Effect of diene type and content on polymer characteristics

ENB and DCPD are mainly used to produce EPDM.

ENB is the most widely used EPDM, which is much faster than DCPD products. Under the same polymerization conditions, the properties of the third monomer affect the long-chain branching, and the order of increase is as follows: EPM

Other factors that influence EPDM by the third diene monomer are:

ENB-rapid vulcanization, high tensile strength and low permanent deformation

DCPD-scorch resistance, low permanent strain and low cost.

With the increase of the third diene monomer, the following effects will appear: the vulcanization speed will be accelerated, the compression set will be reduced, the modulus will be improved, the selection of accelerators will be diversified, the scorch resistance and elongation will be reduced, and the polymer cost will be increased.

Ethylene propylene ratio

The ethylene-propylene ratio can be changed in the vulcanization stage, and commercial ethylene-propylene terpolymers have an ethylene-propylene ratio of 80/20 to 50/50. When the ratio of ethylene to propylene is changed from 50/50 to 80/20, the positive effects are: higher green strength, higher tensile strength, higher crystallinity, lower glass transition temperature, ability to convert raw polymer into pellets and better extrusion characteristics. The bad effects are poor miscibility, poor low temperature characteristics and poor compression deformation.

When the proportion of propylene is high, the advantages are better machinability, better low temperature characteristics and better compression deformation.

Molecular weight and molecular weight distribution

The molecular weight of elastomer is usually expressed by Mooney viscosity. In the Mooney viscosity of EPDM, these values are obtained at high temperature, usually 65438 025℃. The main reason for this is to eliminate any influence (crystallization) caused by high ethylene content, which will mask the true molecular weight of the polymer. The Mooney viscosity of EPDM ranges from 20 to 100. Commercial EPDM with higher molecular weight is also produced, but it is generally oil-filled and mixed.

The molecular weight and its distribution in EPDM can be polymerized in the following ways:

Type and concentration of catalyst and catalyst.

temperature

The concentration of modifier, such as hydrogen.

The molecular weight distribution of EPDM can be determined by gel permeation chromatography at high temperature (150℃) with dichlorobenzene as solvent. The molecular weight distribution is usually called the ratio of weight average molecular weight to number average molecular weight. This value ranges from 2 to 5, depending on the common and highly branched structures. Due to the separation of bonds, the molecular weight distribution of EPDM containing DCPD is wide.

By increasing the molecular weight of EPDM, the positive effects are: higher tensile and tear strength, higher green strength at high temperature, and more oil and filler absorption (low cost). With the increase of molecular weight distribution, the positive effects are: increasing the mixing and milling performance. However, narrower molecular weight distribution can improve curing speed, curing state and injection molding behavior.

Vulcanization type

EPDM can be vulcanized with organic peroxide or sulfur. However, compared with sulfur vulcanization, peroxide crosslinked EPDM has higher temperature resistance, lower compression deformation and improved vulcanization characteristics when used in wire and cable industry. The disadvantage of peroxide vulcanization is its high cost.

As mentioned above, the crosslinking speed and curing time of EPDM vary with the curing type and content. When EPDM is mixed with butyl rubber, natural rubber and styrene-butadiene rubber, the following factors must be considered when selecting suitable EPDM products:

When mixing rubber with butyl, in order to adapt to the vulcanization speed of butyl, it is best to choose EPDM with relatively low DCPD and ENB content, because the unsaturation of butyl is low.

When it is used together with natural rubber and styrene-butadiene rubber, it is best to choose EPDM with ENB content of 8% ~ 10% to meet its vulcanization speed.