Vulcanization is the basic process of preparing vulcanized rubber by cross-linking between raw rubber molecules to form three-dimensional network structure. Different curing systems are suitable for different raw rubbers.
Although there are a lot of literatures about elastomer vulcanization, the research on rubber vulcanization is still going on deeply and persistently. The main purpose of the study is to improve the mechanical properties and other properties of vulcanized rubber, simplify and improve the technological process, and reduce the release of harmful substances during vulcanization. In order to evaluate the new ideas about vulcanization in recent years, the vulcanization system currently used is briefly described.
Traditional vulcanization system
Unsaturated rubber usually uses the following vulcanization system.
1. Sulfur, organic disulfide and polysulfide, thiazole, diphenylguanidine, zinc oxide and stearic acid are the main vulcanizing agents. This is the most common curing system. However, the thermal oxidative aging resistance of vulcanized rubber is not high.
* 2. Alkyl phenolic resin.
3. Polyhalides (such as hexachloroethane used for polybutadiene rubber, styrene-butadiene rubber and nitrile rubber) and hexachloroparaxylene.
4. Bifunctional reagents [such as quinone, diamine, azo and phenylazo derivatives (for butyl rubber and ethylene propylene rubber)].
5. Bismaleimide, diacrylate. Bivalent metal acrylate (methacrylate), pre-polyether acrylate.
6. Organic peroxide for vulcanizing saturated rubber.
When different kinds of saturated rubber are vulcanized with saturated rubber, different vulcanization systems can be used. For example, when vulcanizing EPDM, organic peroxide is used together with unsaturated crosslinking agent, such as triallyl isocyanurate (vulcanizing agent TAIC).
When vulcanizing silicone rubber, organic peroxide can also be used. Vulcanization of vinyl silicone rubber can be carried out in the presence of catalyst (Pt).
The general vulcanization method of fluororubber is described in relevant monographs.
Rubber containing halogen atoms or rubber containing functional groups, such as chloroprene rubber, chlorosulfonated polyethylene and chlorinated butyl rubber, is the most commonly used chlorine-containing rubber.
Vulcanized chloroprene rubber usually adopts a mixture of ZnO and MgO, and ethylenethiourea (NA-22), Qiu Lan disulfide, o-tolylbiguanide (accelerator BG) and sulfur are used as vulcanization accelerators. When chlorosulfonated polyethylene is vulcanized, the following vulcanization system can be used.
1. mixture of alumina, lead oxide and magnesium oxide, magnesium oxide and pentaerythritol ester, and Qiu Lan tetrasulfide (accelerator TRA) and accelerator DM as vulcanization accelerator.
2. hexamethylenetetramine, adipic acid, sebacic acid and magnesium oxide.
3. The reaction product of organic amine and epoxide.
The following systems can be used for vulcanization of chlorinated butyl rubber:
1. mixture of zinc oxide with stearic acid, magnesium oxide, Qiu Lan and benzothiazole disulfide;
2. Mixture of vinyl dithiocarbamate with zinc oxide and magnesium oxide.
3. A mixture of hydroxymethyl phenolic resin and zinc oxide.
4. Zinc dialkyl dithiocarbamate.
5. Hydroxyaromatic compounds (resorcinol, hydroquinone, etc.). ) (at room temperature)
Metal oxides and peroxides, polyols, diamines and polyamines, epoxides, diisocyanates and polyisocyanates are commonly used to vulcanize carboxyl rubber.
Zinc oxide sulfur curing system, halogen-containing organic matter and epoxy resin are often added to amino-containing vulcanized rubber.
Oxides (such as MnO2 _ 2 and Sb _ 2O _ 5), sulfides (such as CuS) and sulfur-containing polyamines (used for acrylate rubber) are commonly used when curing nitrile-containing rubber.
In the absence of vulcanizing agent, due to the reaction between reactive functional groups in the polymer. It is also possible to form a chemical cross-linked bond network in the elastomer. For example, at high temperature, this happens in a mixture of PVC and NBR.
Non-traditional vulcanization system
In recent ten years, the main research contents are the vulcanization process itself and the ecological problems of vulcanized rubber products in the process of use, as well as improving the vulcanization process, reducing the tendency of scorch and reversion, and popularizing cold vulcanization. Also pay attention to prevent curing agent, especially sulfur, from frosting in the finished product. By selecting suitable curing system and curing conditions, some achievements have been made in improving the properties of vulcanized rubber and products.
Reduce the ecological harm when using the vulcanization system.
Sulfur is usually contained in the vulcanization system of unsaturated rubber, so a series of measures are being taken to prevent sulfur from flying during weighing, such as granulation. Usually, the polymer of sulfur with dicyclopentadiene, styrene and its oligomer is used to eliminate sulfur frosting. It is also suggested to use a mixture of sulfur and polymer resin, a solution of sulfur in cyclic hydrocarbon oil, sulfur-containing oligobutadiene, and a reaction product of sulfur with 5- ethylene-bicyclo [9.2. 1] heptyl -2- ene and indane. Adding N- trichloromethyl thiosulfamic acid to sulfur vulcanizate can reduce frosting. * * * polymers of ethylene and alpha-olefins, alpha-olefin rubber and ethylene-propylene rubber can be vulcanized with bismaleimide derivatives containing Cl, S or SO2 groups without sulfur vulcanization.
The ecological harm of nitrosamines is well known. Therefore, diamine-based accelerators are dangerous because they produce volatile nitrosamines. The least dangerous are zinc dibenzyl dithiocarbamate and dibenzyl Qiu Lan disulfide. Sulfonamides, tetramethylthiuram disulfide and other lower alkyl Qiu Lan accelerators can be used in limited amount (0.4-0.5%). For tire compound, accelerator DZ(N, N'- dicyclohexyl -2- benzothiazole sulfenamide) is often used, and the mixture of disulfide and tetrabenzyl thiuram bismaleimide can also be used. Xanthate derivatives without nitrogen atoms will not produce nitrosamines when combined with a small amount of commonly used accelerators. The mixture of dialkyl (C 1-5) phosphoryl trisulfide, N- trichloromethyl sulfinyl phenyl sulfenamide, benzothiazole disulfide (accelerator DM) and zinc dibenzyl dithiocarbamate will not produce nitrosamines. The use of vitamin C and vitamin E additives can reduce the generation of nitrosamines in general pickling systems. From the ecological point of view, piperazine derivatives such as 1, 1'- dithiobis (4- methylpiperazine) are the main promoters to replace amine promoters, and Qiu Lan and urea are used together, so it is more appropriate to use 2- 15% polythiazole and 15-50% bismaleimide. It is suggested that alkyl dithiophosphate be used as vulcanization accelerator of EPDM, and nitrosamines will not be produced at this time. Pretreatment of filler and ZnO with ammonia or n- amine can prevent the formation of nitrosamines. Adding a small amount of CaO, Ca(OH)2 and Ba(OH)2 into polybutadiene-styrene butadiene rubber vulcanizate can also prevent the formation of nitrosamines.
Improving the technology and application performance of vulcanized rubber
In recent years, various curing systems used to improve the properties of vulcanized rubber, especially unsaturated rubber, have increased significantly.
Unsaturated rubber
It is suggested that carboxyl rubber be vulcanized with divalent metal salts of phthalic acid and trimellitic acid such as calcium, magnesium and zinc. The rubber compound containing this metal salt can resist scorching, and the strength of vulcanized rubber can reach 65438±08 MPa. Triethanolamine can vulcanize the polymer of butadiene, acrylonitrile and isopropoxycarbonyl methyl methacrylate with Fe(OH)3 as the accelerator. The obtained vulcanized rubber is used to prepare oil-resistant and benzene-resistant products. -
NBR can be crosslinked with multifunctional vinyl ester. When these rubbers are vulcanized with peroxide, phenyl acrylate or naphthyl dimethacrylate are often used as vulcanizing agents, and the obtained vulcanized rubber has heat resistance and high wear resistance. Pentaerythritol tetraethylene ester is usually used to lower the curing temperature.
It is suggested that a new vulcanizing agent based on ethylenethiourea be used to vulcanize NBR, butyl rubber, chloroprene rubber and EPDM. Vulcanizing NBR with low molecular weight phenolic resin can form interpenetrating network and play a reinforcing role. Quinone-oxime (sodium, zinc, aluminum) salt and p-quinone-dioxime (sodium, zinc) salt can be used to vulcanize polybutadiene rubber.
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Vinyl trimethoxysilane is usually used to vulcanize EPDM and EPDM. Peroxide vulcanization in the presence of phenolic peroxide oligomer can improve the high temperature properties and physical and mechanical properties of EPDM. Epdm can also be vulcanized with epoxy oligomer containing peroxy group; At this time, the viscosity of carbon black compound decreased and the strength of vulcanizate increased.
Alkoxy-terminated polysiloxane is often used for dynamic vulcanization of polypropylene and EPDM, and the obtained thermoplastic elastomer has high heat resistance.
The vulcanization of carboxyl nitrile rubber, a new vulcanization accelerator, is a mixture of thiophosphate disulfide and accelerator DM or N- ethylene oxide -2- benzothiazole sulfenamide. The dinitro oxidation derivatives of xylene and anthracene can increase the vulcanization speed by 1-3 times, and the vulcanization temperature is only 60-80℃. (The original requirement was 140- 160℃), and the obtained vulcanizate was resistant to thermal oxidative aging. In order to accelerate the vulcanization of hydroxynitrile rubber, bis (diisopropyl) thiophosphate trisulfide was also used to prepare vulcanized rubber with increased network density.
Using benzimidazole derivatives containing aromatic substituents or double bonds can not only improve the thermal oxidative aging resistance of NBR, but also improve its strength and dynamic fatigue resistance. In addition, benzimidazole derivatives with heterocyclic yoke double bonds are often added to NBR compound, so as to improve the strength, thermal and oxidative aging resistance and dynamic properties of rubber.
Adding phosphorus or polyphosphonyl hydride to NBR CKH-26 and organic dithiophosphoric anhydride to NBR CKH- 18 can accelerate vulcanization and keep the stability of vulcanized rubber. A new polymer vulcanization accelerator for isoprene rubber and cis-polybutadiene rubber can be prepared by polycondensation of hexamethylenediamine and sulfur. This kind of vulcanization accelerator has a wide vulcanization flat area, which can improve the physical and mechanical properties of vulcanized rubber. Alkyl triethylammonium bromide is often used as vulcanizing agent for isoprene rubber CKH-3 and nitrile rubber CKH-26. At this time, the strength of CKH-26 vulcanizate can be increased from 4.5MPa to 6.8MPa.
It is suggested to adopt a new vulcanizing agent based on aliphatic aromatic acids and aliphatic acids or alcohols and 2-(2', 4'- dinitrophenyl) thiobenzothiazole, and its decomposition induction period is 140- 165min at 160℃.
In order to improve the vulcanization speed of unsaturated rubber, a second accelerator, such as the condensate of butyraldehyde and aniline, is often added. When vulcanizing natural rubber and styrene-butadiene rubber, 1- phenyl-2,4-biuret and Qiu Lan are used. Natural rubber can be vulcanized with 2-(2,4-dinitrophenyl) mercaptobenzothiazole and a second accelerator. The properties of the vulcanizate obtained are similar to those cured with 2- benzothiazole -N- sulfur code. In order to improve the fatigue life of natural rubber, amido phosphate oligomer is often added to the accelerator. The existence of 1, 3- butadiene and 2- vinylpyridine * * * polymers accelerates the vulcanization speed of natural rubber and improves the strength of vulcanized rubber. This method can also improve the vulcanization speed of cis-polybutadiene rubber and nitrile rubber, and reduce the scorch tendency.
Adding derivatives of copper salicylamide and aniline to EPDM can increase the vulcanization speed by 0.2-0.5 times. At the same time, the strength, fatigue resistance and heat resistance of vulcanized rubber were improved.
The strength of SBR vulcanizate can be improved by using phosphatized fatty acid alkyl amide (1 times). If sodium dialkyl dithiophosphate and polyquaternary ammonium salt are added to sulfur, there will be synergistic effect in vulcanizing isoprene rubber, and the strength of vulcanized rubber can reach 23.6MPa.
A new vulcanizing agent for natural rubber and styrene-butadiene rubber is 2- m-diazobenzene sulfonamide. Compared with ordinary phosphoramidite accelerators, they can improve the vulcanization rate faster, the vulcanization degree is higher and the induction period is longer.
Besides dicumyl peroxide, benzoquinone ether can also be added to the "cold" vulcanization of butyl rubber in hot water. The curing time at 60℃ is 9d, and the curing time at 95℃ is 12h and 3h respectively.
New methods to reduce the scorch rate In recent ten years, many new compounds have been used to reduce the scorch rate. The mixture of tetrabenzyl Qiu Lan disulfide and sulfenamide and 2- pyrazine sulfenamide is effective for most rubber vulcanized with sulfur. For the blends of SBR and BR, tetramethyl isobutyl monosulfide from Qiu Lan is recommended. It is suggested that zinc dimethacrylate be used as the blend of NBR and EPDM. Phenothiazine is very effective when nitrile rubber and isoprene rubber are vulcanized with peroxide, while phenothiazine and 2,6-di-tert-butylcresol are effective when EPDM is vulcanized.
Reducing reversibility It is suggested to use derivatives of diethyl phosphate to reduce reversibility. In addition, hexamethylene bis (sodium thiosulfate), pentachloro-β-hydroxyethyl disulfide, a mixture of bis (citramide) and C3 hexahexene, diphenyl dithiophosphate (Ni, Sn, Zn), 1- phenyl-and 1, 5- diphenyl -2 can also be used.
It is also effective to use a mixture containing 0. 1% to 0.25% bis (2,5-polythio-1, 3,4-thiadiazine), 0.5% to 0.3% bis (maleimide) and 0.5% to 3% sulfenamide. There is no reversion when alkoxysilane vulcanizing agent containing sulfur yellow and olefin groups is used.
Using the mixture of fatty acid zinc and aromatic acid zinc salt can not only reduce the reversion of vulcanization, but also improve the dynamic properties of vulcanizate. Adding 1 3 bis (lemon iminomethyl) benzene can not only reduce the reversion of vulcanization, but also improve the tear resistance and strength of vulcanizate.
A new method of using sulfur curing activator is to combine ZnO(3-5 parts by mass) and stearic acid (1 part by mass) as sulfur curing activator. At present, various methods are used to reduce the amount of zinc oxide, even to replace zinc oxide. For example, heating the mixture of accelerator M, accelerator TT, ZnO and stearic acid to 100- 105℃ can reduce the ZnO content in rubber to 2 parts by mass.
Sometimes, a mixture of SiO2 _ 2 and ZnO treated by a polymer surfactant solution is also used, so that the amount of ZnO can be reduced, and inorganic fillers coated with ZnO have also been used.
In some cases, the leftovers from battery production can be used to replace zinc oxide, or a mixture of calcium, zinc and silicon dioxide can be used.
Saturated rubber
In recent years, many new vulcanization systems have been developed for the vulcanization of saturated rubber. For example, when NBR is vulcanized with resin, adding maleimide can reduce the risk of scorch.
Some people have introduced new vulcanizing agents for vulcanizing saturated EPDM, namely aliphatic bis (allyl) alkane diol and bis (allyl) polyvinyl alcohol. Using these vulcanizing agents can improve the vulcanization speed and improve the physical and mechanical properties of vulcanized rubber. -
Halogen rubber
In order to improve the vulcanization technology of halogen-containing rubber, people have done a lot of research work. Chlorine-containing rubber vulcanized with metal oxides has weak cross-linking bonds. Many researches aim at overcoming this shortcoming, such as suggesting adding diammonium distearate [RNH(CH2)3NH2] to ZnO and MgO? 2C 17H3COOH can improve the mechanical properties. Many chlorine-containing rubbers, such as chloroprene rubber, chlorinated butyl rubber, chlorosulfonated polyethylene rubber and epichlorohydrin rubber, use a mixture of 2,5-dithiol-1, 3,4-thiadiazine and organic polysulfide derivatives of MgO.
If chloroprene rubber contains silica treated with silane, polysulforganosilane and thiourea derivatives can be used as vulcanization system. The vulcanized rubber thus prepared has high tear resistance.
Polyguanidine is usually used instead of zinc oxide when curing chloroprene rubber. 2- mercapto -3- tetra -4- oxothiazole mercaptan is a new vulcanizing agent loaded on molecular sieve, which can improve the fatigue resistance and heat resistance of rubber and can replace toxic ethylenethiourea. Chloroprene rubber can also be vulcanized by a vulcanization system containing yellow sulfide, Qiu Lan and oligomeric amine. In use. When chloroprene rubber was vulcanized with 3- chlorine 1 2 propylene oxide and Qiu Lan oligomer, the scorch stability of the compound was improved, and the physical and mechanical properties of the vulcanizate were also improved.
It is also suggested to use ethylenethiourea as vulcanizing agent for chloroprene rubber (it can also be used to vulcanize EPDM).
A lot of research work has discussed the new vulcanization method of chloroprene rubber. Includes replacing metal oxide with metal sulfide and making the modified filler participate in the presulfurization process.
For example, K354 carbon black treated with hydrogen sulfide has a sulfur content of 6-8% and can also react with metals (Ba, Mo, Zn, etc.). ) Sulfide and chloroprene rubber form cross-linking bonds on the surface of filler. Compared with mass-produced vulcanized rubber containing ZnO and MgO, the strength of the former is increased by 50%, the fatigue resistance is increased by 65,438 0.5 orders of magnitude, the permanent deformation is reduced to 2%, and the hardness, thermal oxygen aging resistance, oil resistance and chemical corrosion resistance are improved. The above effects can also be achieved by using chloroprene rubber, fumed silica modified with ethylene bis (dithiocarbamate) ammonium and carbon black K345(50 parts by mass). Compared with the mass-produced rubber vulcanized by ZnO and MgO, the strength, tear resistance and wear resistance of the experimental vulcanized rubber are improved, the dynamic fatigue performance is improved by 65438 0.5 orders of magnitude, and the heat resistance and acid resistance are improved by 2-9 times.
The mechanical properties of chloroprene rubber can be fundamentally improved by using specially treated fumed silica (30 parts by mass) as filler. Firstly, fumed silica was treated with SiCl4 _ 4, and OsiCl3 _ 3 group was generated on its surface to replace OH group. Then it was modified by chelating salts of zinc ethylene bis (dithiocarbamate) and ethylene bis (Qiu Lan disulfide). The rubber strength using this system is 5MPa higher than that of mass-produced rubber, with permanent deformation of 3-6% and tear strength of 43-6 1KN/m (mass-produced rubber is 9.5KN/m). The wear resistance of the tested rubber is 65438 0.5 times higher than that of the blended rubber, and the fatigue resistance is 2 times higher. Chlorinated butyl rubber, brominated butyl rubber and chlorine-containing and bromine-containing polymers of isoolefin and n-alkyl styrene can be vulcanized with bis (Qiu Lan pentamethylene tetrasulfide) and ZnO. Tert-hexyl peroxybenzoate can be used to vulcanize halogenated butyl rubber without releasing methyl bromide. Chlorinated and brominated butyl rubber vulcanizates, as well as chlorine-containing and * * * * * containing polymers of isoolefins and alkylstyrene, have high strength and high heat resistance when vulcanized with amine salts of triazine thiols.
Chlorinated butyl rubber containing inorganic filler can be vulcanized by di-o-methylguanidine salt and diphenol boron salt of alkylphenyl disulfide. The strength of the vulcanizate can be increased from 2.4MPa to 7.5MPa. The combination of metal sulfide and sulfur to vulcanize chloroprene rubber also has good results. At this time, the rubber formula should contain carbon black and 10 part of fumed silica modified with ammonia. The strength of vulcanizate can be increased from 18MPa to 22MPa, the permanent deformation can be reduced to 8%, the tear strength is1kloc-0/kn/m (86kN/m for mass production of rubber), the wear resistance is improved almost twice, and the fatigue resistance is improved more than three times. It has a similar effect on epichlorohydrin rubber, chlorosulfonated polyethylene and its polymers. Metal sulfides are also used to vulcanize chlorinated butyl rubber, but with the participation of dehydrated zeolite. Zeolite has high adsorbability, which can absorb the released gas, thus making vulcanizate more compact and improving its performance. For example, the strength is increased from 18MPa to 24MPa, the tear strength is 90kN/m (46kN/m for mass-produced rubber), the wear resistance is increased by 1 times, and the repeated deformation fatigue resistance is improved by two orders of magnitude.
Chlorinated rubber (neoprene, chlorosulfonated polyethylene, etc.). ) can be made of p-quinone dioxime, pyrolusite and FeCl3? The mixture of 6H2O is vulcanized at low temperature.
/silicone rubber
Generally speaking, the choice of silicone rubber curing system is very limited. However, there are many patents about silicone rubber vulcanization. Most patents relate to room temperature curing. This vulcanization requires the use of a storage tank with a rubber layer and a electroplating bath, and the surface of the electrical appliance needs to be coated with an insulating layer. When rubber is used for sealing or other purposes, it usually needs room temperature vulcanization.
The simplest way to vulcanize silicone rubber at low temperature is to use silica with OH groups on its surface. This filler is treated with chlorine-containing heptamethylcyclotetrasiloxane in the presence of aprotic solvent. In the presence of dibutyltin laurate catalyst, polydimethylsiloxane-α, ω-diol filled with fumed silica can also be vulcanized at room temperature. Some kinds of polysiloxanes can be vulcanized in the presence of silica treated with hydroxyl-terminated oligomers containing silicon. When sulfur-containing antioxidants are used, saturated elastomers containing silicon-terminated alkoxy groups can self-vulcanize, forming silicon-oxygen bonds. Vulcanized rubber has good heat resistance.
The research paper expounds the general principle of cold vulcanization of silicone rubber which has nothing to do with filler modification:
The [1] crosslinking bond is formed in a "one-component" system consisting of raw rubber with OH end groups and RSiX3 crosslinking agent. (where X is hydroxyl, imino, silazane or ethylenediamine). These groups are hydrolyzed by moisture in the air to generate OH groups, and then condensed to generate Si-O-Si bonds without catalyst.
[2] In the presence of catalysts (derivatives of Pt, Sn and Ti), a cross-linked bond network was formed in a "two-component" system consisting of two kinds of silicone rubber with interactive reaction groups.
[3] When there is filler but no catalyst, the end groups of two or more kinds of silicone rubber may interact.
In fact, the second and third cases are self-vulcanizing compounds with the same properties but different active groups.
At present, a large number of patents describe different aspects of these methods. But most of them are just differences in details. For example, a rubber that can be printed 12× 104 times and used in laser printers (strength is 5MPa) is methyl silicone rubber or diphenyl silicone rubber, and even other silicone rubbers are used without catalyst. The system composed of two kinds of dimethyl silicone rubber, heptamethyl vinyl silicone rubber and carbon black containing terminal hydroxyl and trimethylsilicon can also be vulcanized. In addition, the vulcanization reaction can also be carried out in the rubber mixture of silicone rubber containing terminal hydroxyl groups and polysiloxane and ON=CR2 crosslinking agent. When there is no water, hydroxyl-terminated dimethyl silicone rubber can be vulcanized with difunctional, trifunctional and tetrafunctional derivatives of silane.
Silicone rubber containing silanol end groups can be vulcanized with vinyl (trihydroxy) silane in the presence of inorganic fillers. Silicone rubber containing trimethylsilanol end groups can be vulcanized with vinyl trimethoxysiloxane in the presence of catalyst. The curing condition is 20℃×7d. The strength of vulcanizate reached 5.6MPa. The compound can be used to make coatings and adhesives, and also can be used in electronics, medical care and food industries.
The rubber mixture consisting of polysiloxane containing olefin end groups, polysiloxane containing SiH groups, catalyst and silicone adhesive can also be vulcanized. Its vulcanized rubber has excellent adhesion with thermoplastics and resins. In the presence of Pt catalyst and NH3, the mixed compound of olefin-containing polysiloxane can also be vulcanized. The compression set of vulcanized rubber is very low. !
N- heterocyclic silane, such as bis (trialkylhydroxysiloxy) pyridine, is an adhesion promoter for metal and plastic bonding. In the presence of platinum catalyst and filler, they can be used to vulcanize the mixture of vinyl terminated siloxane and polyhydroxysiloxane. The duration of vulcanization reaction is 7d. The shear strength combined with aluminum is 3.8MPa)
* * * Rubber vulcanization
Rubber with various reactive functional groups (with different properties) can be vulcanized with harmless special vulcanizing agent, which is not only suitable for low-temperature vulcanization of silicone rubber, but also suitable for high-temperature vulcanization of other rubbers. For example, chlorinated natural rubber and hydroxyl nitrile rubber were vulcanized to obtain oil-resistant wear rubber. Chlorinated butyl rubber and hydroxyl nitrile rubber can be vulcanized at 180℃ without vulcanizing agent. Hydroxynitrile rubber and chlorosulfonated polyethylene rubber, including rubber filled with carbon black, can also be vulcanized. The blend of PVC and hydrogenated nitrile rubber can be vulcanized at 180-200℃ to form amino and ether crosslinking bonds. The mixture of epoxidized natural rubber and chlorosulfonated polyethylene filled with carbon black can be vulcanized without vulcanizing agent. Vulcanized rubber has extremely high strength and tear strength, and good wear resistance. The blends of epoxidized natural rubber, chloroprene rubber and carboxyl nitrile rubber can be vulcanized without crosslinking agent. Polyvinyl chloride and carboxyl nitrile rubber were vulcanized at 180℃, and the vulcanized rubber had high oil resistance and wear resistance.
Therefore, it is one of the main directions to solve the ecological problems caused by vulcanization and improve the properties of vulcanized rubber in recent ten years to choose matching rubber with active functional groups and vulcanize it without using special crosslinking agent.