端硅烷基液体氟弹性体的合成与固化及性能

SYNTHESIS,CURE AND PROPERTIES OF SILOXY-TERMINATED LIQUID FLUOROELASTOMERS

用两步法合成了端硅烷基液体氟弹性体：（1）以端羧基液体氟弹性体和五氟苯酚为原料,通过Steglich反应制备了端五氟苯酚酯液体氟弹性体;（2）端五氟苯酚酯液体氟弹性体与γ-氨丙基三乙氧基硅烷发生取代反应,制备端硅烷基液体氟弹性体.用FTIR,1H-NMR,19F-NMR和GPC对端羧基液体氟弹性体、端五氟苯酚酯液体氟弹性体和端硅烷基液体氟弹性体的化学结构进行了表征.端硅烷基液体氟弹性体可在室温下进行湿度固化,固化膜的Tg 随着固化前硅烷封端液体氟弹性体相对分子质量的增加而降低.固化膜具有很好的耐酸,航空煤油,非极性溶剂等化学药品性,且高分子量的固化膜的耐航空煤油,环己烷,盐酸性能优于低分子量的固化膜.固化膜具有较好的疏水疏油性,与水的接触角为91°~114°,与丙三醇的接触角为89°~111°.固化膜具有较好的耐热性能,5%热失重温度T5在215~280 ℃,800 ℃的残炭率为23.44%~38.69%.

Siloxy-terminated fluoroelastomers were prepared through two-step reactions：（1） pentafluorophenol ester-terminated fluoroelastomer was synthesized by Steglich reaction using liquid carboxyl-terminated fluoroelastomer and pentafluorophenol as raw material; （2） the siloxy-terminated fluoroelastomer was prepared by substitution reaction with γ-aminopropyl triethoxysilane.The chemical structure of liquid carboxyl-terminated fluoroelastomer,pentafluorophenol ester-terminated fluoroelastomer and siloxy-terminated fluoroelastomers was characterized by FTIR,1H-NMR,19F-NMR and GPC.The carboxyl content measurement of pentafluorophenol ester-terminated fluoroelastomer was carried out by automatic potentiometric titration,and the conversion reaction is above 99.9%,which indicates that the reaction was completely conducted.The Siloxy-terminated fluoroelastomer can be cured at room temperature according to the mechanism of moisture-cure.Cured siloxy-terminated fluoroelastomer films with low Tg is usually obtained from higher molecular weight of fluoroelastomer.The cross-linked films obtained from higher molecular weight of fluoroelastomer have better tensile strength and elongation at break.The cured films have excellent chemical resistance,such as acid resistance,jet fuel oil resistance and cyclohexane resistance.And the cured films with higher molecular weight have better chemical resistance than those of the lower molecular weight.The observed contact angles were 91°~114° for water and 89°~111° for glycerol,which indicates that the cured films have good hydrophobic and hydrophilic properties.It is seen that the initial temperature （T5） of cured films appears in the range of 215 to 280 ℃ and the char yield at elevated temperature of 800 ℃ remains at 23.44%~38.69%.