A fluorine rubber formula is generally composed of raw rubber, acid absorbent, vulcanizing agent, accelerator, reinforcing filler, processing aid and so on.
(1) Raw rubber
The performance of domestic fluorine rubber and foreign fluorine rubber is basically the same, but there are some differences in processing performance. The processing performance of domestic rubber is poor, mainly due to the higher Mooney viscosity, which affects the processing fluid of the rubber.
Domestic fluorine rubber 26 is equivalent to VitonA of DuPont in the United States, fluorine rubber 246 is equivalent to VitonB, and many foreign fluoro rubber raw rubbers have been added with vulcanizing agents. Well vulcanizing agent.
(2) curing agent
Vulcanization is to make the fluororubber cross-link to a certain degree, so that it has good performance. The fluororubber vulcanization can be performed by the ionic addition mechanism of nucleophile, or by the free radical mechanism by peroxide or radiation.
Amine compounds (1 #, 3 # vulcanizing agent) vulcanized fluorine rubber can solve the requirements of general products; using 2 # vulcanizing agent can solve the processing of glue.
In the sealing products, in order to make it have a small compression deformation value, a phenolic compound should be preferably used as a vulcanizing agent. Such as hydroquinone, bisphenol A, bisphenol AF, etc., together with corresponding accelerators, to meet high-level performance requirements.
In solving the resistance of corrosive media, it is recommended to use peroxide vulcanized fluorine rubber.
(3) acid absorbent
Acid absorbers are also called stabilizers. It is to solve the corrosion and pollution of metals caused by hydrogen fluoride produced during the processing of fluorine rubber, so that the vulcanization reaction proceeds smoothly. Ca (OH) 2 and the like. Generally, MgO, CaO, ZnO, PbO, and dibasic lead phosphite are used. Each of them has its own characteristics: MgO has good heat resistance; PbO has good acid resistance; CaO has small compression deformation; it is beneficial to eliminate air bubbles; ZnO and dibasic lead phosphite have improved fluidity and good water resistance; Ca ( OH) 2 has a small compression deformation. Ca (OH) 2 and active MgO are added. In the phenolic vulcanization system, a low compression deformation rubber can be obtained. In short, it is necessary to choose a suitable acid absorbent to meet the requirements of actual performance.
(4) Reinforcing filler
Fluorine rubber is a rubber with self-reinforcing properties. Due to different performance requirements and uses, adjustments need to be made through the reinforcement and filling system to make its functions and costs meet the needs of users. The general dosage is between 10-30 parts. At present, the commonly used reinforcing fillers include thermal cracking carbon black (N-990), spray carbon black, white carbon black, calcium sulfate, barium sulfate, calcium oxide, and carbon fiber.
N990 carbon black or spray carbon black imported from Canada has achieved good processing technology and corresponding physical properties in black products.
Add 20 parts of carbon fiber fluoro rubber, the rubber material has good fluidity, after processing vulcanized complex shape products, its appearance is better than N-990 and spray carbon black, and the surface is smooth. Due to the large thermal conductivity of the carbon fiber rubber compound, it is suitable for the use of high-speed moving rubber parts. It should be noted that the cost of adding carbon fiber is high and its elongation is low. Color fluororubber products can use white carbon black, titanium white, calcium fluoride, calcium carbonate, etc., and the corresponding rubber can be obtained by matching the corresponding pigment. However, when processing compression-type sealing products, when selecting color raw materials, pay attention to the reasonable matching of pigments and high temperatures, and also control the compression deformation value of the rubber to make the product suitable for the work needs under compression.
(5) Processing Aid
Processing aid is a great progress in the processing of fluorine rubber in recent years. It can improve the mixing process of fluorine rubber, prevent scorch, and improve the fluidity and extrusion performance of rubber without affecting the performance of the rubber. And can prevent sticking rollers, sticky molds during processing, and play the role of external release agent.
In the processing of fluororubber, new processing aids such as fluorowax, low-molecular polyethylene, zinc stearate, Ws280, and palm wax have appeared, providing a new means for processing and application of fluororubber. It is added in 1-2 servings.