Composition and performance of FKM
- FKM is a series of fluoroelastomer materials based on fluorocarbons defined by ASTM International Standard D1418. The current FKM is mainly based on VDF monomers, which are copolymerized with monomers such as HFP, VDF, MVE and TFE to obtain binary or terpolymers. In the combination of VDF and HFP, in order to obtain amorphous elastomer products, the proportion of HFP must be higher (19 to 20 mol% or even higher). In the combination of VDF/HFP/TFE, the ratio of the three must also be in a certain area to produce elastomer, as shown in the triangle diagram (Figure 1).
Figure 1. Fluoroelastomer composition of polymers made of vinylidene fluoride (VF2), hexafluoropropylene (HFP), and tetrafluoroethylene (TFE) 
- The swelling resistance of fluorocarbon elastomer is directly related to the fluorine content in the molecule, as shown in Table 1. Copolymers of VDF and HFP have excellent resistance to oils, fuels, and aliphatic and aromatic hydrocarbons, but they exhibit relatively high swelling in low molecular weight esters, ketones and amines, which is due to VDF Exist in their structure.
Table 1. Effect of fluorine content on solvent swell 
|FKM Polymer ||% Fluorine||Benzene/21°C ||Aviation hydraulic fluid /21°C |
|VDF/HFP||65||20||171 (@100 °C)|
Note: FKM, fluorocarbon elastomer; VDF, vinylidene fluoride; HFP, hexafluoropropylene; TFE, tetrafluoroethylene; CSM, cure site monomer; PMVE, perfluoromethylvinyl ether.
- VDF-based fluoroelastomers have very good resistance to strong acids. For example, they remain tough and elastic even after prolonged exposure to anhydrous hydrofluoric acid or chlorosulfonic acid at 150°C. The general chemical resistance of FKM is shown in Table 2.
Table 2. General chemical resistance of FKM 
|Outstanding Resistance||Good to Excellent Resistance||Poor Resistance|
|Hydrocarbon solvents||Low-polarity solvents||Strong caustic|
|Automotive fuels||Oxidative environments||(NaOH, KOH)|
|Engine oils||Dilute alkaline solutions||Ammonia and amines|
|Apolar chlorinated solvents||Aqueous acids||Polar solvents|
|Hydraulic fuels||Highly aromatic solvents||(Ketones)|
|Aircraft fuels and oils||Water and salt solutions||(Methyl alcohol)|
- Using electrospinning technology, the fluorocarbon elastomer can be prepared into a non-woven superhydrophobic nanofiber film. On this basis, the composite FKM fiber membrane that can be prepared by combining organically modified nano-clay and fumed silica has super-hydrophobicity, anti-icing and super-physiological saline at the same time. In addition, the composite film can still maintain the durability of the film material under ultraviolet irradiation. This robust superhydrophobic membrane has a wide range of applications in the automotive, aerospace and petrochemical industries. 
- Fluorocarbon elastomers can be used in the production of wearable devices. Even in the case of prolonged contact with skin oils and frequent exposure to light, the wear and discoloration are also very low, while ensuring high comfort and stain resistance.
- Considering the high cost, FKM is suitable for special applications that have very high requirements for high temperature and corrosion resistance to chemicals and heat transfer oil.
- Anestis L. Logothetis, Progress in Polymer Science 14 (1989) 251-296.
- Jiri George Drobny, Technology of Fluoropolymers, 2009, p96-97.
- Shilpa Simon, Ankit Malik, Balasubramanian Kandasubramanian, Materials Focus 7 (2018) 194-206.
Get in touch with us
If you have any services of interest, you are welcome to contact us to discuss the solutions that best suit your requirements.
※ Please kindly note that our services are for research use only.