| Fluorosilicone rubber is one of special silicone rubber that consists mostly of methyl-trifluoropropylsiloxane. The Si-O-Si backbone structure gives the rubber good flexibility and thermal stability, while the trifluoropropyl pendant group gives the rubber excellent oil resistance and solvent resistance due to strong polarity of F atom. But the trifluoropropyl group could be decomposed at a lower temperature compared with methyl group, thus the flurosilicone rubber exhibits a poorer heat resistance and ageing resistant performance than PDMS. With the expansion of fluorosilicone rubber applications, a higher requirement on thermal stability, oil resistance and damping properities of silicone rubber was raised. With Ph unit introduced, the co-polymer shows good high temperature stability caused by the rotating resistance and the high temperature resistance free radical. This article introduced the methylphenysiloxane chain into the methyl-trifluoropropylsiloxane chain hoping to enhance the thermal stability of fluorosilicone rubber. The other properties such as damping properties were studied as well.In this paper poly(trifluoropropylmethylsiloxane-co-methylphenylsiloxane) (PMFS-PMPS) were prepared via anionic ring opening polymerization using KOH as catalyst. D3F and DnPh are chosen as monomers, while the D3FVi is introduced to improve curing properties. By doing so, the co-polymerization conditions on D3F and DnPh were studied. PMFS-PMPS with high molecular weight and lower by-products could be prepared with the dosage of catalyst at 30ppm and the reaction temperature at 90℃. Also the acetic acid was added into raw rubber to neutralize. The method with extraction by petroleum ether and vacuum were used to remove by-products. The removal difficulties caused by high boiling point of DnPh were solved successfully.A series of PMFS-PMPS with different methylphenylsiloxane (Ph) unit mole percent were prepared. The impact of the Ph unit mole percent with molecular weight was investigated via GPC and automatic viscosity tester, the results indicates that the molecular weight increases with Ph unit mole percent increases while poly-dispersity index shows opposite trend. The structure of PMFS-PMPS is researched by IR,1H NMR,29Si NMR and DSC. These tests show that Ph unit has been introduced to the co-polymer successfully and the Ph unit mole percent in co-polymer is consistent with the DnPh mole percent. The UV spectra were used to test Ph unit mole percent in co-polymer. On the basis of those research, vinyl-terminated PMFS-PMPS co-polymers with small molecular weight were prepared, and the structure and the thermal stability were studied.On the basic of above-mentioned research, a series of cured silicone rubber with the formula that 100 portion raw rubber,50 portion SiO2 and 1.5 portion DBPMH were prepared, the influence of Ph unit mole percent to thermal stability, damping property and oil resistance were investigated. The thermal stability of cured rubber enhanced not obviously in inert atmosphere. On the contrary the thermal stability enhanced evidently in air atmosphere due to different mechanism of thermal degradation. With the increase of Ph unit mole percent and the molecular weight, the thermal stability in inert atmosphere and air atmosphere both improved, and the cross-link density of cured rubber enhanced. Therefore the hardness and tensile strength improved, effective damping temperature range broadened, the oil and solvent resistant weakened as wll. In conclusion, the oil resistance of PMFS-PMPS co-polymer is poorer compared to PMFS, but the thermal stability, the damping properties and the tensile strength are improved. So the PMFS-PMPS co-polymer is a new type silicone rubber material with good damping properties and oil resistant performance. |
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