Several commonly used rubber accelerators

According to the different chemical structure, rubber promoters can be divided into thiazoles, tyuram, sulfoamides, guanides, dithiocarbamates, aldehydes, xanthates and thiourea and other eight categories.

Thiazoles This is the earliest of the organic promoters. It is an acid accelerator.

It is characterized by high vulcanization activity and good aging resistance and fatigue resistance. Therefore, it is widely used in the rubber industry and consumes a large amount. There are two main varieties as follows.

(1) 2 mercaptan benzothiazole trade name for accelerator M.

This product is light yellow powder, bitter taste, non-toxic, stable storage. For the general accelerator, natural rubber and diene general synthetic rubber with rapid promotion, vulcanization flatness is good, vulcanization critical temperature of 125℃, mixing the possibility of encephalitis burning.

Easy to disperse in rubber, no pollution, but not suitable for food rubber products. The dosage of the first accelerator is 1~2 parts, and the dosage of the second accelerator is 0.2~0.5 parts. Can also be used for natural rubber plasticizing agent.

(2) dibenzothiazole disulfide trade name for promoter DM.

This product is light yellow powder, bitter taste, non-toxic, stable storage. Its characteristics and uses are similar to M, but the critical vulcanization temperature is 130℃. Above 140℃, the activity increases, has better after-effect, vulcanization operation is safe.

It is often used with other accelerators to enhance its activity.

Two, autumn am this kind of accelerator is acidic. It is an overspeed accelerator.

They include primary, disulfide and polysulfide kulams.

Thiuram disulfide can be used for sulfur-free yellow vulcanization with vulcanizing agent. As an accelerator generally used as a second accelerator, with thiazole and secondary sulfonamide accelerator and used to improve the rate of vulcanization.

When used with secondary sulfonamide accelerators, it can delay the reaction time of the rubber material, and the reaction can proceed particularly fast after the vulcanization, and the vulcanization degree of the rubber is relatively high. This production system is particularly important in low sulfur vulcanization.

The physical and mechanical properties and aging resistance of vulcanizates with thiuram accelerator are affected by the ratio of accelerator and sulfur dosage. Generally speaking, the amount of sulfur is normal, the fixed elongation strength of vulcanized rubber is higher, and other physical and mechanical properties are better;

When the amount of sulfur is low and the amount of promotion is large, the heat aging property of vulcanized rubber can be improved.

The most commonly used type of thiuram accelerator is tetramethyl Thiuram disulfide, the trade name is promoter TMTD, short for promoter TT. It can be used as accelerant, also can be used as curing agent. When used as accelerant dosage is generally 0.2~0.3.

Tertiary sulfonamides This is a class of delayed accelerators, acidic.

It has the characteristics of long coking time and high vulcanization activity.

Vulcanized rubber is relatively high degree of vulcanization, excellent physical and mechanical properties, aging resistance is quite good.

The compound has a broad vulcanization flatness. Due to the development and application of synthetic rubber and the popularization and application of high dispersion furnace carbon black, a good delay accelerator is needed.

Therefore, this kind of accelerant occupies a very important position and becomes the fastest developing and the most promising kind of accelerant in recent years.

At present, the use of a variety of promoters in the world, far to the secondary transverse amide class, among which a large number of applications are CZ, NOBS, NS, DZ and OTOS, they are mercaptan benzothiazole derivatives.

(1) N-cyclohexyl-2-benzothiazolidesulfamide trade name for accelerator CZ. This product is light yellow powder, slightly odor, non-toxic, specific gravity is 1.31~1.34, melting point is not lower than 94℃, stable storage.

The critical vulcanization temperature is 138℃, and it has the advantages of excellent coke resistance and fast vulcanization speed. This product has slight discoloration, spray cream, vulcanized rubber has excellent aging resistance. The general dosage is 0.5~2 copies.

(2) n-oxy-diethyl-2-benzothiazolidesulfonamide or 2- (4-morphinylthiolate) benzothiazole trade name NOBS accelerator. This product is light yellow powder, non-toxic. The specific gravity is 1.34~1.40. Melting point is 80℃~86℃. It gradually decomposes when exposed to heat, so it should be stored at low temperature.

When the storage time is more than 6 months, the coke dumping of the rubber material increases, the critical temperature of vulcanization is above 138℃, the coke burning time is longer than the accelerator CZ, and the operation is safer. This product is easy to disperse in the rubber, no spray cream, slight discoloration. The general dosage range is 0.5~2.5, and with 2~0.5 parts of sulfur yellow.

(3) N-tert-butylbenzothiazolsulfamide trade name for accelerator NS. This product is light yellow powder with special smell. The specific gravity is 1.29, and the melting point is no lower than 105℃. Its performance and usage are basically similar to that of accelerator CZ, but its delayed effect is greater in natural rubber. Slight discoloration and contamination.

(4) N, N- dicyclohexyl -2-2 benzothiazole sulfamide trade name for accelerator DZ. This product is brown yellow powder, odorless. The specific gravity is 1.2. Melting point not lower than 90℃. Stable storage.

This product disperses well in rubber. Vulcanization flat performance is similar to that of accelerator CZ. The dynamic physical and mechanical properties of vulcanized rubber are better, and the strength of elasticity and fixed elongation is high. However, vulcanized gum can not be used to make products in contact with food because of its bitter taste. Its dosage range is generally 0.5~1, sulfur for 2.5.

Four, guanidine this kind of accelerator is alkaline, medium speed accelerator used earlier.

The vulcanization flatness is poor, the vulcanization starting point is slow, the coke burning time is short, the vulcanization operation safety is poor, has the pollution.

Rarely used alone or as a first accelerator. In general, it is also used as a second accelerant. Its vulcanized rubber tensile strength and rebound rate is relatively high, low heat generation.

The main varieties commonly used are diphenylguanidine, trade name accelerator D or accelerator DCP. This product is white powder, non-toxic, but irritating when contact with skin, specific gravity is.13~1.19. Melting point not lower than 144℃.

The critical vulcanization temperature of this product is 141℃, and the vulcanization flatness is poor. Polluting, not suitable for white light products and food contact rubber products. As the first accelerator dosage of 1~2, with thiazole accelerator and used as the second accelerator dosage of 0.1~0.5.

Five, dithiocarbamates This is a class of super speed accelerator, acid.

Vulcanization speed is particularly fast, the vulcanization curve is flat, the range is small, the burning time is short, so the rubber material in the process of processing is easy to produce early vulcanization phenomenon, vulcanization operation is not safe.

Improper control of curing conditions, it is easy to occur under-sulfur or over-sulfur phenomenon.

If used properly, the physical and mechanical properties of vulcanized rubber and aging resistance are superior, no pollution.

Suitable for high temperature short time vulcanization of thin products, room temperature vulcanization products and latex products, the most commonly used is the following zinc salt varieties: zinc dimethyl dithiocarbamate trade name for accelerator PZ, also known as accelerator ZDMC.

This product is white powder, tasteless, non-toxic. But contact with the skin can cause inflammation.

The specific gravity is 1.65-1.74. The melting point is 240~255℃. The critical vulcanization temperature is about 100℃, and the vulcanization activity is similar to the accelerator TT, but the activity is larger at low temperature and the tendency to char is larger. This product is easy to disperse in rubber, products tasteless, non-toxic, no pollution. Mainly used for latex products, natural vulcanized glue, adhesive cloth products and cold vulcanized products, light and color products, edible rubber products. In the amount of rubber latex material is generally 0.3~1.5.

Hexaldehydes and amines This class of accelerators are condensates of aliphatic aldehydes or amines (aliphatic or aromatic amines), which are acidic.

The vulcanization activity and vulcanization performance of different varieties were different. Its activity range is generally from quasi-super to slow grade. Has good flatness, scorch time is not long.

The characteristic is that the vulcanized rubber obtained has excellent aging resistance. Among them, the less active promoters (such as hexamethyltetramine) are often used as the second promoter of thiazoles or secondary sulfonamides. Only butyraldehyde aniline condensation is a strong accelerator, and the tyuram class of promoters produced as the first accelerator.

(1) hexamethyltetramine trade name for accelerator H.

This product is white to light yellow crystalline powder, almost odorless, bitter taste. It can irritate the skin. The specific gravity is 1.3. When heated to 263℃, it sublimates and partially decomposes. A little deliquescence. The critical temperature is 140℃, low vulcanization temperature is not too lively, small risk of burning. Used as a secondary accelerator. No discoloration, no pollution, not easy to decompose. Mainly used for transparent and thick-walled products.

(2) n-butyl aldehyde and aniline condensation trade name for accelerator 808.

This product is brown red or amber thick oily liquid, has a special smell. Specific gravity 0.94~0.98. In the air for a long time the color becomes darker and the proportion increases. But the effectiveness is the same. Isolated air storage stability.

Vulcanization flatness is high, the critical temperature is 120℃, the most suitable vulcanization temperature is 120~160℃. Good dispersion in dry glue. Suitable for rubber and hard rubber containing recycled rubber.

Seven, xanthate class This is a particularly high activity of speeding accelerators, promoting effect is even faster than the ammonium salt of dithiocarbamate.

Vulcanization flat range is very small. Generally used for latex and low temperature vulcanized glue, only special cases for dry glue.

The commonly used variety is zinc n-butyl xanthate, trade name is promoter ZBX.

This product is white powder Lin, has a special smell, non-toxic. The specific gravity is 1.40. Heat decomposes.

During storage, there is a tendency to slow decomposition, so it needs to be stored at low temperature (below 10℃). For super accelerator, no pollution. Eight, thiourea other new varieties of accelerators are currently committed to the research of new accelerators, in order to produce high vulcanization promoting efficiency, good processing safety, anti-retrograde can be good, high aging resistance of the accelerator.

In addition, the varieties of sulfur donors increased gradually, and non-sulfur cross-linked systems emerged continuously. And promoters known to be toxic, such as ethylthiourea, are being phased out.

(1) triazine accelerator one of the most important is double (2-ethylamine - 4-diethylamine - triazine -6) disulfide, this product than the ordinary accelerator to promote high efficiency, curing speed, and processing safety.

The vulcanization rate of natural rubber is similar to that of accelerator NOBS, and the processing safety is between NOBS and CZ.

The dosage is less. In the natural rubber containing 1.5~2.35 parts, only 0.3 parts can replace 0.5 parts of sulfamide.

This promoter can improve sulfur under low dosage of sulfur china.nearby the adhesive back to the original resistance, can be used for production and acrylonitrile butadiene styrene butadiene rubber, isoprene rubber.

(2) thiocarbamoyl sulfoamides this kind of accelerators are mainly n-oxy-diethyl thiocarbamoyl - n-oxy-diethyl sulfoamides, this kind of accelerators with high operating safety, curing speed, promoting effect.

Suitable for styrene butadiene rubber, nitrile butadiene rubber, EPDM and other general synthetic rubber.

The vulcanization rate of the compound with 0.67 parts is faster than that with 1 part sulfonyl accelerator.

And can obtain satisfactory operation safety performance. Above 149℃, the activity is very large, and below 149℃, a small amount of promoters NOBS, M or DM can be added.

(3) thiophosphoryl accelerant - (diethylthiophosphoryl) trisulfide - This accelerant can be used as a sulfur donor in natural rubber.

When replacing sulfur in part or in whole, the heat resistance of vulcanized rubber can be improved, and the vulcanization reversion and compression deformation property can be improved during high temperature vulcanization.

In EPDM rubber is an excellent accelerator, safe operation, fast vulcanization, excellent heat resistance and no spray frost, excellent compression deformation resistance.

Unlike many other accelerators and sulfur and sulfur donors, it will not cause degradation of polyester fiber when it is vulcanized with rubber.