The choice of FKM fluorine rubber vulcanizing agent
A, vulcanization system
23 and 26 type fluorine rubber is saturated fluorocarbon compounds, cannot use sulphur vulcanization, but in the second amine curing agent vulcanizer, diols and under the action of organic peroxide, vulcanization reaction.
Amine curing agent vulcanizates, low deformation, acid resistance is poor; Two benzoyl peroxide acid resistance is good, but the heat resistance is poorer, process performance is not good. Currently used vulcanizing vulcanizing agent is very much, mainly is the no. 3, 4, 5 (polyol) and two benzoyl peroxide.
3 vulcanizing agent full name: N, N - double - 1, 6 - hexamethylenediamine cinnamon fork;
4 vulcanizing agent full name: double - (4 - ammonia hexyl cyclohexyl) methane amino formate
5 vulcanizing agent full name: hydroquinone (hydroquinone)
23 type fluorine rubber with two benzoyl peroxide as curing agent, mainly used in acid products; 26 fluorine rubber is often used to heat, heat the oil products, mainly with amine curing agent curing agent (3).
Amine curing agent 3 vulcanization agent, the product is the rubber has plasticizing effect, good process performance, heat resistance and compression can be vulcanized rubber. 4 vulcanizing agent was developed by over 246 type fluorine rubber appear, failed to widely used; With 5 vulcanizing agent Viton
E development of the analysing of vulcanizing agent.
1. 2 amine curing agent:
Of fluorine rubber molecules exist - CH2 - CF2 - link, because of fluorine atoms is extremely strong electronegativity, in heat and alkaline compounds (such as amine, magnesium oxide, etc.), is easy to emerge the hf form easy polarization double bond, this kind of fluorine-containing olefin structure easily with nucleophilic reagents such as amine and phenolic bonus, and gave birth to clinch a deal the cross-links. Ordinary diamine or polyamine in fluorine rubber vulcanization starts quickly reduced the rubber processing safety, generally adopt the hidden multiple amine, to play its role in high temperature, so that delay in vulcanization, cyclic carbamate is the hidden multiple amine.
With the increase of dosage of curing agent, vulcanizates increase of hardness, strength, elongation and compression permanent deformation is reduced, the strength retention of increase slightly after high temperature aging, keep elongation rate has dropped significantly.
In rubber with adding acid receptor (namely acid absorption agent), in order to effectively neutralizing precipitation in the process of fluorine rubber vulcanization hydrogen fluoride (or hydrogen chloride). Hydrogen fluoride or the presence of hydrogen chloride can interfere with the rubber crosslinking and serious corrosion of equipment, further due to acid absorption agent can promote the improvement of vulcanization crosslinking density, give vulcanizates better thermal stability, so also known as the surfactant or stabilizing agent. The effect of acid and alkali absorption strength, the strength of alkaline, the income the higher the degree of cure of the vulcanized rubber, hardness, high strength, elongation and compression permanent deformation is small, but the more alkaline, processing safety the worse, the more easy to coke burning. The commonly used acid with magnesium oxide, calcium oxide, lead oxide, dibasic lead phosphite, acid absorption agent has great influence on the performance of the vulcanizates, should according to the requirements of the rubber and appropriate choice. Who is given priority to with heat resistant formula appropriate USES magnesium oxide as the acid absorption agent, when demand low compression permanent deformation at the same time, and calcium oxide or magnesium oxide and calcium oxide are available, and require acid formula using lead oxide as acid absorbent. When using a combination of zinc oxide and dibasic lead phosphite, the heat resistance, but has good resistance to water and high temperature resistant performance of the water vapor. The amount of oxide generally is 15 ~ 25.
Diamine curing agent its process safety, heat aging and compression permanent deformation resistance are poor. Have proved that this kind of vulcanization system has its unique properties, such as metal and glue is firm, which is often used as some special products, such as the adhesion of rubber and metal products.
2 hydroxy vulcanizing agent: 2.
This type of vulcanizing system is currently used most frequently, most commercial of fluorine rubber were joined this kind of curing agent. Rubber processors and add metal oxide acid acceptor and packing, made of rubber.
Dihydroxy vulcanizing agent for nucleophilic reagent, vulcanization system when using dihydroxy vulcanization system has higher crosslink density, so make the vulcanizates improved heat resistance and deformation resistance.
With dihydroxy vulcanizing vulcanizing fluorine rubber must have proper alkali promoter exists in order to complete. Has been used in industry, is developing rapidly the promoter of the main season for phosphorus salt and quaternary ammonium salt, its varieties, such as benzyl triphenyl phosphorus chloride, benzyl octyl phosphorus chloride and other season phosphorus salt and tetrabutyl ammonium hydroxide and its salt, is a kind of compound and its derivatives, such as quaternary ammonium salt.
Dihydroxy make rubber vulcanization system has good processability and scorch resistance, fast curing rate and sulfide has excellent compression permanent deformation resistance, but the tear resistance, especially in hot tear resistance is not ideal.
3. The peroxide vulcanizing agent:
Peroxide vulcanizing fluorine rubber to make the performance of the water vapor resistance of fluorine rubber improved. It generated in vulcanization of the volatile by-products of insoluble volume is small.
2, reinforcing filling system
Fluorine rubber without adding filler when its vulcanizates which has high strength, reinforcement filling system, though it has certain reinforcing effect, but mainly to improve process performance, improve the products of heat resistance, hardness, compression permanent deformation and reduce the cost is reduced. Add 5-80 clay in fluorine rubber, graphite, talc, mica powder can decrease the shrinkage rate of vulcanized rubber. Adding inorganic filler is calcium fluoride fluorine rubber, the dosage general up to 20-35, its resistance to high temperature (300 degrees) aging performance is better than that of carbon black and other fillers, but the process performance is poor spray carbon black, both with and can get a comprehensive performance good rubber. Calcium carbonate and barium sulfate is also used, the former by good insulation and the latter can obtain low pressure change. They generally 20-40 quantities.
26 type fluorine rubber packing for the most commonly used method of carbon black particles in the hot tear (MT), carbon black, carbon black and Austin spray carbon black (made by bituminization oil products), filling the carbon black can give good rubber mixing, extruding and moldability, cracking of particles in the filling of carbon black rubber and has excellent heat resistant performance. The amount of carbon black, unfavorable and overmuch, the hardness of vulcanized rubber increases with the increase of the amount of carbon black, with an increase in the amount of carbon black, rubber process performance greatly reduced viscosity rise, more important is also will increase the brittleness temperature, vulcanized rubber carbon black dosage Yun usually not more than 30. Although high abrasion furnace black can improve tearing resistance and abrasion resistance, but due to the rubber liquidity becomes poor and lead to a marked increase in the hardness of vulcanized rubber, it is rarely used. Slot method of carbon black due to its acidic manifested, delay sulfide generally don't have to.
26 type fluorine rubber using white carbon black, especially in the gas phase silica rubber, process performance is poorer, sulfur rubber heat resistant, wear resistant and high temperature compression deformation is not good, so rarely used. Usually just using the peroxide for vulcanizing agent in some cases, the use of precipitated silica, dosage of 15 ~ 30, the situation can be used in the preparation of light color rubber. When using calcium fluoride to improve heat aging resistance of the rubber is very good, is better than that of carbon black and other mineral filler, but poor performance and acid and poor performance. With carbon fiber and fibrous magnesium silicate (needle talcum powder) can make the high temperature strength and thermal aging properties of vulcanized rubber was improved, but in terms of process performance of particle cracking carbon black is a bit poor, especially the application of acicular powder rubber stratification, bring certain difficulty to die, that with the carbon fiber or spray carbon black and will improve. Filled with carbon fiber
The vulcanizates of the compression permanent deformation than carbon black particles in the hot tear is small, tear strength is also quite big, using carbon fiber as filler, due to its good thermal conductivity, to a large extent, overcome the thermal dissipation and sticking problem in the process of mixing, and high speed for fluorine rubber oil seal parts.
23 type fluorine rubber by 1.5 ~ 3 second benzoyl peroxide as curing agent, mainly used in acid products. Due to carbon black with peroxide has the effect that the inhibitor, acyl groups, thus impede curing reaction, the physical and mechanical properties of the vulcanizates below with white carbon black as filler, so 23 type fluorine rubber rarely used carbon black as filler. When using carbon is carried out by gas phase method for silica filler, the room temperature vulcanized rubber the highest tensile strength and hardness, but fumed silica resistance to heat the old poor performance for a long time. At 200 ℃ under tensile strength after aging for a long time to maintain the best calcium fluoride and titanium dioxide, but calcium fluoride acid performance is poor, substitutes and titanium dioxide of precipitated silica as filler, its dosage for 5 ~ 15 of precipitated silica or titanium dioxide 20 ~ 30.
3, the operating system
General plasticized material may not apply to fluorine rubber, because they not only can make the heat resistance of vulcanized rubber and chemical stability, and in the second period of plasticized material in high temperature vulcanization process often can be steamed out, when the content of larger severe contraction deformation even foaming sulfide product, so the demanding of plasticized material, type of 26 good fluorine rubber softener for fluorine and silicone oil or high viscosity fluorine silicone oil with high viscosity and the combination of phenolic resin, which can reduce the hardness of vulcanized rubber vulcanizates properties such as heat resistant, oil resistant and solvent resistance. Using a small amount of low molecular fluorine rubber methods can improve mixing and moldability, and does not affect the heat resistant properties of the vulcanizates. Add 3 ~ 5 in 23 type fluorine rubber polytrifluorochloroethylene of low molecular weight (fluorine wax) as the softener, can reduce the viscosity of the rubber, to improve the mixing, extrusion, calendering process performance, such as strength of room temperature vulcanized rubber at the same time, the 200 ℃ aging for a long time and nitric acid resistant, oil resistant and does not affect performance