The Preparation, Structure And Properties Of Fluororubber/Silicone Rubber Blends

In recent years, as automobiles, machinery, aviation, aerospace and chemical industry have developed in the direction towards high performance, low power consumption and long life, general rubber such as nature rubber, chloroprene rubber, and acrylonitrile butadiene rubber etc can not satisfy thermal stability and oil resistance in new rubber products. Fluororubber (FKM) has outstanding thermostability, oil and corrosion resistance, and silicone rubber (MVQ) exhibits high temperature stability, low temperature flexibility and good processability, which leads to increased application of FKM and MVQ. However, the disadvantages of FKM are lack of low temperature resistance and bad processability and MVQ has a lack of oil resistance. Fluorosilicone rubber gradually aroused people's attention due to have the advantages of FKM and MVQ, but fluorosilicone rubber can not be widely used due to its high price and unsteady synthesis technology. FKM/MVQ blends were prepared with FKM and MVQ rubber by mechanical blending. The mechanical properties of FKM/MVQ blends are similar to those of fluorosilicone rubber but the cost of FKM/MVQ blends is cheaper than that of fluorosilicone rubber. As a result, FKM/MVQ blends can be used to substitute fluorosilicone rubber.The effect of rubber blending, curing and post-curing technologies on curing behaviors, mechanical properties, dynamic mechanical properties and crosslinking density of FKM/MVQ blends was investigated. It is shown that heat treatment to silicone/silica compounds can improve mechanical properties of FKM/MVQ blends. When the curing temperature is 165℃and post-curing time is 4h at 250℃, FKM/MVQ blends show superior mechanical properties. DMA results show that there is little effect of curing and post-curing temperature on Tg of fluororubber and silicone rubber phase.The effect of fluororubber varieties, blend ratio, curing agents and reinforcing fillers on properties of FKM/MVQ blends was investigated. The blends were characterized by DMA, TG, SEM and RPA. The results show that mechanical properties of FKM teropolymer/MVQ blends are better than those of FKM bipolymer/MVQ blends. As the proportion of MVQ phase increases from 0 to 100%, the brittle temperature of FKM/MVQ vulcanizates decreases from -20.5℃to -64.2℃, and the compression set decreases.When the blend ratio of FKM/MVQ is 50/50, the blends shows good synthetical peroperties. FKM/MVQ blends show superior mechanical properties when DCP content is 1 phr. The blends cured with DCP/TAIC show better mechanical properties and low temperature resistance than those cured with bisphenol AF/BPP/DCP and 3# curing agent/DCP. The mechanical properties, heat ageing properties and low temperature resistance of FKM/MVQ blends reinforced with fumed silica are better than those of the blends with other fillers such as precipitated silica, calcium silicate, diatomite and CaF2. The mechanical properties, heat ageing properties and oil resistance of FKM/MVQ blends increase with increasing of the content and specific surface area of fumed silica. FKM/MVQ blends show better physical properties with the addition of 40 phr fumed silica with specific surface area of 220m2·g-1. TG shows that thermal stability of the blends increases with the increasing proportion of MVQ phase. The thermal stability of the blends cured with DCP/TAIC is better than those cured with bispheonol AF/BPP/DCP and 3# curing agent/DCP. DMA results show that Tg of FKM phase increases from -1.8℃to 11.1℃with increasing of vibrated frequency from 1 to 50 Hz, but there is little change in Tg of MVQ phase. RPA results show that the blends with silica shows more obvious Payne effect than the blends with other fillers. And Payne effect increases with increasing of fumed silica content and its specific surface area. Tanδof FKM/MVQ vulcanizates increases with increasing of strain, however it decreases with increasing of temperature. The mechanical properties, low temperature resistance and processing properties of FKM/MVQ blends are superior to fluorosilicone rubber, but the oil resistance of FKM/MVQ blends needs to be further improved.MVQ-g-TFEMA and FKM-g-A174 were prepared by chemical grafting reaction initiated by DCP, which are used as compatibilizers of FKM/MVQ blends. The effect of compatibilizer content on physical properties of FKM/MVQ blends was investigated. And the blends are characterized by FT-IR, DMA and TG. The blends with addition of 4.6wt% MVQ-g-TFEMA or 11.8wt% FKM-g-A174 show superior mechanical properties. The brittle temperature decreases from -36.8℃to -43.6℃, and the change in mass of FKM/MVQ blends after ASTM 3# oil immersion decreases from 22.3% to 16.3% with increasing of FKM-g-A174 content from 0 to 19.6wt% and the brittle temperature decreases from -36.8℃to -48.3℃and the change in mass decreases from 35.3% to 22.5% with MVQ-g-TFEMA content from 0 to 11.8wt%. TG results show that thermal stability of FKM/MVQ blends increases with addition of compatibilizers content. The compatibilizing effect of FKM-g-A174 on FKM/MVQ blends is better than that of MVQ-g-TFEMA.