Formula and processing technology of fluorine rubber

- Nov 25, 2019-

Fluororubber is a synthetic rubber containing fluorine atoms. It has the characteristics of high temperature resistance, oil resistance and resistance to various chemicals. It is the best medium resistance of all elastomers and has excellent weather resistance and weather resistance. Ozone resistance. One of its main varieties is a copolymer of perfluoropropene and vinylidene fluoride, the foreign trade name viton, the other is a copolymer of chlorotrifluoroethylene and vinylidene fluoride, the foreign trade name Kel-F (rubber), they High temperature resistance, Kel-F maximum application temperature is 205 ° C, excellent corrosion resistance, resistant to various acids (including medium concentration of oxidizing acid), but solvent resistance is not as good as fluoroplastics, can be used for high temperature and resistance in chemical industry Corrosive environment, also used as rubber coatings and adhesives. Fluororubber can replace the need for anti-corrosion treatment, but the F4 spray method and the lining method can not operate the medium and large equipment. From the cost point of view, the fluororubber anticorrosion is also lower than the F4 anti-corrosion.

  The formulation of fluorine rubber is composed of fluorine rubber, acid acceptor, vulcanizing agent, accelerator, reinforcing filler and processing aid. The performance of domestic fluororubber and foreign fluororubber is basically the same, but the processing performance is somewhat different. The processing performance of domestic rubber is poor, mainly because the Mooney viscosity is high, which affects the poor fluidity of rubber processing.

  The domestic type 26 fluororubber is equivalent to VitonA of DuPont, USA, and the 246 type fluororubber is equivalent to VitonB of DuPont of the United States. The vulcanizing agent of the fluorine rubber plate is to make the fluorine rubber have a certain degree of crosslinking, so that it has good performance. The vulcanization of the fluorine rubber sheet can be carried out by using an ionic addition mechanism of a nucleophilic reagent, or by a radical mechanism by a peroxide or a ray. The vulcanizing agent of the fluorine rubber sheet is different from the vulcanizing agent used for other rubber sheets. The use of amine compounds (1#, 3# vulcanizing agent) vulcanized fluororubber can solve the requirements of general products; using 2# vulcanizing agent can solve the processing of glue. In the fluororubber sealing article, in order to have a small compression deformation value, a phenol compound should be preferably used as a vulcanizing agent. Such as hydroquinone, bisphenol A, bisphenol AF, etc., with the appropriate accelerator to suit high-level performance requirements. In solving the resistance of corrosive media, it is recommended to use peroxide-vulcanized fluororubber.

  The addition of an acid acceptor to the fluorine rubber is also referred to as a stabilizer. It is to solve the corrosion and pollution of hydrogen by hydrogen fluoride generated during the processing of fluorine rubber, so that the sulfurization reaction can proceed smoothly. Generally, MgO, CaO, ZnO, PbO, and dibasic lead phosphite are used, and the amount thereof is generally 5 to 10 parts. Their addition has its own characteristics: MgO has good heat resistance; PbO has good acid resistance; CaO has small compression deformation; it is advantageous for eliminating bubbles; ZnO and dibasic lead phosphite, the fluidity of the rubber is improved, and the water resistance is good; OH)2 has small compression deformation, and Ca(OH)2 and active MgO are added. In the phenolic vulcanization system, a low compression deformation compound can be obtained. In short, choose the right acid absorber to meet the actual performance requirements.

  Fluororubber is a self-reinforcing rubber. Due to the different performance requirements and uses of the fluorine rubber, it needs to be adjusted by the reinforcing and filling system to adapt its functions and costs to the needs of users. Generally used in an amount between 10-30 parts. At present, commonly used reinforcing fillers are generally thermal black carbon (N-990), spray carbon black, white carbon black, calcium sulfate, barium sulfate, calcium oxide, carbon fiber and the like. Color fluororubber products can use white carbon black, titanium white, calcium fluoride, calcium carbonate, etc., and the corresponding pigments can be used to obtain the corresponding rubber compound. However, when processing a compression type sealing product, when selecting a color material, it is necessary to pay attention to the reasonable matching of the pigment and the high temperature, and also to control the compression deformation value of the rubber material, so that the product can be adapted to the work under compression.

  Processing aid is a major advancement in the processing of fluororubber in recent years. It can improve the mixing process of fluororubber, prevent scorch, and improve the fluidity and extrusion performance of the rubber compound without affecting the performance of the rubber compound. And can prevent the sticking roller and the sticking mold during processing, and play the role of an external mold release agent. In the processing of fluorine rubber sheets, new processing aids such as fluoro wax, zinc stearate, Ws280 and palm wax have appeared, which provides a new means for the processing and application of fluorine rubber sheets.

  The processing and equipment of the fluorine rubber and the processing method are the same as those of general rubber. Due to the structural characteristics of the fluororubber, its processing properties are poor.

  Mastication: Raw rubber is thinned 10 times in an open mill with a roll distance of 0.3~0.5mm, and the compounding agent can be added to the roll.

  Mixing: The capacity of fluororubber is smaller than that of synthetic rubber; the roller temperature is generally controlled at 40-60 ° C; the order of feeding: raw rubber → acid absorbing agent → processing aid → filler → vulcanization accelerator. After the addition of the compounding agent, evenly and thinly, the triangle bag, the roll, and then the film.

Vulcanized rubber vulcanization should be carried out in two steps: one-stage vulcanization 165-170 ° C × 10 min; two-stage vulcanization 230 ° C × 24 h (to ensure the gradual heating, after 230 ° C, constant temperature time.

Fluororubber products must be completed by professional and skilled workers. There should be no omissions in every part of the operation process, otherwise it will lead to product defects, which will make it impossible to make up for the difficulties.