Perflurane rubber (FFKM), whose structure combines the main chain of tetrafluoroethylene (PTFE) with the branch chain and connecting parts of perfluoromethyl vinyl ether (PMVE), not only exhibits excellent resistance to high temperature and chemical corrosion (resistant to more than 1,600 chemical substances), but also retains the elastic properties of rubber. FFKM products are widely used in high-end industrial fields such as aviation, aerospace, petroleum, chemical and atomic energy, especially as seals, performing well in harsh environments such as rocket engine fuel, hydrazine, oxidizer, nitrous oxide, fuming nitric acid and freon-21.

At present, the synthesis technology of FFKM in China is still in the stage of experimental exploration. Although Zhonghao Chenguang Chemical Research Institute has successfully developed the key raw material of FFKM - perfluoromethyl vinyl ether, the synthesis process of rubber is still under test. This trial focused on the formulation and process optimization of FFKM raw rubber, aiming to develop a perflurane compound with excellent high temperature stability, low compression permanent deformation and excellent medium resistance.

Materials and methods

1.1 Test materials

PFR94 Perflurane rubber: from Solvay, Italy.

Performance comparison materials: including 3M's perflurane E19467 and 2375.

1.2 Formulation Research

1.2.1 Selection of compounding agent

Sulfur vulcanization system: Due to the high saturation and fluorine content of FFKM, sulfur vulcanization is not applicable. Organic peroxides, organic amine derivatives or dihydroxyl compounds are commonly used as vulcanizing agents. Radiation vulcanization has not been industrialized. In industrial production, the bisphenol AF/BPP system provides stable rubber mixing, while the double 25+TAIC system shows good corrosion resistance and high temperature steam resistance, which has become the current mainstream.

Reinforcing filler: FFKM itself has high strength, reinforcing agent is mainly used to improve the process, reduce costs and control hardness, heat resistance and compression permanent deformation, commonly used semi-reinforcing carbon black.

Auxiliaries: Special auxiliaries developed by Solvay can significantly improve the mechanical properties and processability of FFKM.

1.2.2 Formula design

Based on the above analysis, the specific design formula is shown in Table 1 below.

1.3 Manufacturability research

1.3.1 Key points of quality control

Cleaning and equipment: Ensure that the rubber mixing machine and the environment are clean, it is best to use special equipment, otherwise it needs to be thoroughly cleaned.

Cooling and operation: Open the rubber mixing machine, adjust the cooling water to moderate, control the roll distance, thin the raw rubber, evenly wrap the roll, add the premixed powder in batches, avoid cutting, adjust the roll distance timely, and cool the sheet after mixing.

Temperature management: Pay attention to temperature control during mixing, avoid exceeding 50 ° C, and continue after cooling if necessary.

Storage: The compound should be spread out to room temperature before storage to avoid scorching caused by stacking.

1.3.2 Performance Testing

FFKM rubber was prepared according to the design formula, the test pieces and small bean samples were pressed under specific vulcanization molding conditions, and the tensile and physical properties were tested according to national standards, and compared with other brands of rubber, and the medium resistance of the new rubber was evaluated within 30 days.

Results and analysis

Table 3 shows that the newly developed FFKM compound is superior to other compounds in tensile strength and elongation at break at room temperature, indicating that its mechanical properties are outstanding. At the same time, the permanent deformation of high temperature compression is significantly reduced, and it can be used stably at 280 ° C, showing excellent high temperature performance. Table 4 confirms its excellent dielectric resistance and meets the first class compatibility standard.

conclusion

The newly developed FFKM compound has reasonable formula, good process performance, excellent high temperature and medium resistance, fully in line with the expected research objectives, and is suitable for the manufacture of high temperature and medium resistant seals.

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