Fluorine rubber is a polymer elastomer with fluorine atoms attached to the carbon atoms of the main chain or side chain successfully developed in the 1950s. Fluorine rubber has excellent heat resistance, weather resistance, ozone resistance, oil resistance, chemical resistance, low gas permeability, and is a self-extinguishing rubber. The disadvantages of fluorine rubber are poor elasticity and cold resistance, poor processability, and quite expensive. For more than 40 years, its performance has been continuously improved, and it has been widely used in various sealing parts, hoses, tapes and fuel tanks that require medium resistance and high temperature resistance, making it an irreplaceable special rubber.

   1 The main properties of fluorine rubber

1.1 Mechanical properties under normal conditions 26-type fluororubber generally has a tensile strength of 10-20MPa after compounding; an elongation of 150%-300%; a tearing strength of 20-40kN/m, but its elasticity is poor. The friction coefficient (0.8) of fluorine rubber is smaller than that of nitrile rubber (0.9～1.5).

1.2 High temperature resistance At present, the high temperature resistance of fluorine rubber is excellent. Fluorine rubber can work for a long time at 200～250℃, and it can work for a short time at 300℃. The heat resistance of F246 is slightly better than that of F26. The tensile strength and hardness of fluorine rubber significantly decrease with increasing temperature. The characteristic of the change of tensile strength and hardness is that below 150℃, it decreases rapidly with the increase of temperature; between 150-260℃, with the increase of temperature, the downward trend is slow.

Performance changes of fluorine rubber at different temperatures:

Performance 24℃ 50℃ 204℃

Tensile strength, MPa 16.8 3.4 2.0

Elongation at break,% 330 120 80

Shore A hardness, degree 75 65 63

1.3 Corrosion resistance Fluorine rubber has excellent corrosion resistance. It has excellent stability to organic liquids, different fuel oils and lubricating oils, and has good corrosion resistance to most inorganic acids, hydrocarbons, benzene and toluene. It is only resistant to low molecular weight esters, ethers, ketones and some amines. Class compound.

1.4 Performance of hot water and superheated steam The stability of rubber to hot water depends not only on the body material, but also on the compounding technology of the rubber. For fluorine rubber, peroxide vulcanized fluorine rubber is superior to amine and phenol vulcanization systems. It should be said that the performance of fluororubber in heat-resistant water and superheated steam is general, and it is not as good as ethylene-propylene rubber. The volume change after immersion in 180℃×24h superheated water does not exceed 10%, and the physical properties do not change much.

1.5 Long-term compression deformation performance Fluorine rubber is used for sealing under high temperature, and compression deformation performance is its key. Viton-type fluorine rubber has been extremely widely used, which is inseparable from the improvement of its compression deformation. In the 1960s and 1970s, DuPont of the United States was committed to improving the resistance of fluororubber to compression deformation and achieved significant results.

1.6 Low temperature resistance performance The low temperature resistance performance of fluorine rubber is poor, and the limit temperature that it can maintain elasticity is -15--20 ℃. As the temperature decreases, its tensile strength becomes greater and it appears strong at low temperatures. When measuring a 2mm thick standard sample, its brittleness temperature is about -30℃; when the thickness is 1.87mm, it is -45℃; when the thickness is 0.63mm, it is -53℃; when the thickness is 0.25mm, it is -69℃. Generally, the service temperature of fluorine rubber can be slightly lower than the brittle temperature. For example, the US military standard MIL-25879D stipulates that the operating temperature is -40～205℃. The temperature limit of fluorine rubber used in aerospace engines abroad is -35℃.

1.7 Weather resistance and ozone resistance The performance of VitonA after 10 years of natural storage is still satisfactory. In the air with an ozone concentration of 0.01%, no obvious cracks appeared after 45 days of action. Its weathering resistance and ozone resistance are also satisfactory.

1.8 Electrical performance The electrical insulation performance of fluorine rubber is not very good, and it is only suitable for use under low frequency and low voltage. Temperature has a great influence on its electrical properties. For example, when it rises from 24°C to 184°C, its insulation resistance drops by 5 orders of magnitude.

1.9 Air permeability The gas solubility of fluorine rubber is relatively large, its diffusion rate is relatively small, and the total air permeability is small. In fluorine rubber, due to the addition of fillers, the voids inside the rubber are filled, so that the air permeability of the vulcanized rubber becomes smaller, which is very advantageous for vacuum sealing. If matched properly, fluorine rubber can solve 10^-7 Pa vacuum sealing.

1.10 Flame retardancy Fluorine rubber can burn when exposed to fire, and will decompose HF gas when burned, which is corrosive and toxic. Self-extinguishing after leaving the fire.

   2 Research on the modification of fluororubber In view of the shortcomings of fluororubber such as elasticity, poor cold resistance and high price, scientific researchers have done a lot of research work to improve rubber properties. There are two main directions for rubber modification: One is through the main chain modification, such as the development of fluoroether rubber and fluorosilicone rubber. The ether bond is introduced into the fluororubber main chain, which increases the flexibility of macromolecules and makes it low-temperature performance. Greatly improved while retaining the original characteristics of fluororubber, but due to the high cost of development and production, its promotion and application are greatly restricted; the second is the combined use of rubber, combining fluororubber with some general rubbers and special rubbers to achieve performance Excellent and low-cost material. Due to the structural characteristics of fluororubber itself, it is difficult to choose a co-vulcanization system, and the unique characteristics of fluororubber will be partially reduced after combined use. Research on combined use at home and abroad is not extensive. Up to now, the combined modification of fluorine rubber mainly remains in the direction of FPM/ACM, FPM/EPDM and so on. However, fluorine rubber has high performance that other rubbers cannot replace. How to improve the shortcomings of fluorine rubber without reducing or even improving its unique characteristics through combined research is still an area worthy of attention.

氟橡胶的改性的研究进展  

   氟橡胶是上世纪50年代研制成功的主链或侧链的碳原子上连有氟原子的高分子弹性体。氟橡胶具有优异的耐热性、耐候性、耐臭氧性、耐油性、耐化学品性，气体透过率低，且属于自熄型橡胶。氟橡胶的缺点是弹性和耐寒性能差、加工性不佳，而且价格颇为昂贵。40多年来，其性能不断改进，使其已广泛地在各种要求耐介质、耐高温的密封部位、胶管、胶布和油箱等获得应用，成为不可替代的特种橡胶。

   1 氟橡胶的主要性能

1.1 常态下的力学性能 26型氟橡胶一般经配合后拉伸强度为10～20MPa；伸长率150%～300%；撕裂强度在20～40kN/m之间，但是它的弹性较差。 氟橡胶的摩擦系数(0.8)比丁腈橡胶的摩擦系数(0.9～1.5)小。

1.2 耐高温性能 目前，氟橡胶的耐高温性能极好。氟橡胶在200～250℃下可长期工作，在300℃时也可短时间工作，F246的耐热性能比F26略好。 氟橡胶的拉伸强度和硬度随温度升高而明显下降。拉伸强度和硬度的变化特点是，在150℃以下，随温度升高而迅速降低；在150-260℃之间，随温度升高，下降趋势缓慢。

氟橡胶在不同温度下的性能变化：

性能 24℃ 50℃ 204℃

拉伸强度，MPa 16.8 3.4 2.0

拉断伸长率，% 330 120 80

邵尔A硬度，度 75 65 63

1.3 耐腐蚀性能 氟橡胶具有**的耐腐蚀性能。它对有机液体、不同燃料油和润滑油的稳定性优异，对大部分无机酸、碳氢化合物、苯和甲苯有良好的抗腐蚀性，仅仅不耐低分子的酯、醚、酮以及部分胺类化合物。

1.4 耐热水和过热蒸汽的性能 橡胶对热水作用的稳定性，不仅取决于本体材料，而且决定于胶料的配合技术。对氟橡胶来说，用过氧化物硫化的氟橡胶优于用胺类和酚类硫化体系的胶料。应该说，氟橡胶的耐热水和过热蒸汽性能一般，它不如乙丙橡胶，在180℃×24h的过热水浸泡后体积变化不超过10%，物理性能没有太大的变化。

1.5 压缩长久变形性能 氟橡胶用于高温下的密封，压缩变形性能是它的关键。维通型氟橡胶所以得到极其广泛的应用，是与它的压缩变形的改进分不开的。美国杜邦公司在20世纪60～70年代致力于提高氟橡胶对压缩变形的抗耐性，取得了显著效果。

1.6 耐低温性能 氟橡胶的耐低温性能较差，它能保持弹性的极限温度为-15 - -20℃。随着温度的降低，它的拉伸强度变大，在低温下显得强韧。在测定2mm厚的标准试样时，其脆性温度在-30℃左右；厚度为1.87mm时为-45℃；厚度0.63mm时为-53℃；厚度0.25mm时为-69℃。一般氟橡胶使用温度可略低于脆性温度。如美国军用标准MIL-25879D中规定使用温度为-40～205℃。国外对氟橡胶在航天发动机中使用温度极限为-35℃。

1.7 耐天候老化和耐臭氧性 VitonA自然存放10年之后的性能仍然是令人满意的。在臭氧浓度为0.01%的空气中，经45d作用未出现明显的龟裂。它的耐天候老化和耐臭氧性也是令人满意的。

1.8 电性能 氟橡胶的电绝缘性能不是太好，只适用于低频低电压下使用。温度对它的电性能影响很大，如从24℃升到184℃时，其绝缘电阻下降5个数量级。

1.9 气透性 氟橡胶的气体溶解度比较大，其扩散速度比较小，总的气透性很小。在氟橡胶中，由于填料的加入，充填了橡胶内部的空隙，从而使硫化胶的气透性变小，这对于真空密封是很有利的。如配合适宜，氟橡胶可解决10^-7 Pa真空密封。

1.10 阻燃性 氟橡胶遇火能燃烧，燃烧时会分解出HF气体，腐蚀性、毒性大。离火即自熄。

   2 氟橡胶的改性研究 针对氟橡胶的弹性、耐寒性差，价格昂贵等缺点，科研工作者做了大量的研究工作，以改善橡胶性能。橡胶改性主要有两个方向：其一是通过主链改性，如氟醚橡胶、氟硅橡胶的开发，将醚键引入氟橡胶主链，增大了大分子的柔性，使其低温性能大大改善的同时保留了氟橡胶原有特性，但由于开发生产成本高，极大地限制了其推广和应用；其二是橡胶并用，将氟橡胶与一些通用橡胶、特种橡胶并用，目的在于获得性能优异而成本较低的材料。由于氟橡胶自身结构上的特点，共硫化体系选择比较困难，且并用后会部分降低氟橡胶独有特性等原因，国内外在并用方面的研究开展得并不广泛。到目前为至，氟橡胶的并用改性主要还停留在FPM/ACM，FPM/EPDM等方向。但氟橡胶具有其他橡胶不可替代的高性能，如何通过并用研究在改善氟橡胶缺点的同时，不降低甚至提高其独有特性，还是一个值得关注的领域。