聚(对亚苯基-1,3,4-噁二唑)纤维表面氟化处理研究

采用氟气(F2)对聚(对亚苯基-1,3,4-噁二唑)(p-POD)纤维表面进行直接氟化处理.衰减全反射红外光谱(ATR-FTIR)和表面电子能谱(XPS)的结果显示,通过直接氟化处理,p-POD纤维较易与F2发生反应,表面大分子链上引入了大量C—F键,表面氟元素含量高达28.2%,且F原子以—CF/C O、—CFH及—CF2形式存在,表明在表面氟化过程中,既有取代反应,也有加成反应.热失重(TGA)结果表明氟化前后p-POD纤维的耐高温性能没有受到影响,X射线衍射图谱(XRD)表明氟化后纤维的聚集态有序性略微增加.氟化前后纤维的断裂强度基本无变化,在体积分数为20%的硫酸溶液中的人工加速酸老化条件下,氟化后纤维在老化120 h后的断裂强力保留率在80%以上,相比氟化前的纤维提高了约90%,即耐酸性得到明显改善.推测表面氟化处理改善p-POD纤维耐酸性的机理是氟化后p-POD纤维表面N元素含量降低,抑制了溶剂化过程;纤维表面致密程度得到提高以及F原子与酸液形成氢键,从而阻止噁二唑环的质子化,延缓了老化进程.

SURFACE FLUORINATION OF POLY (p-PHENYLENE-1 , 3,4-OXADIAZOLE) FIBER

The surface of poly(p-phenylene-1,3,4-oxadiazole)(p-POD) fiber was fluorinated directly by fluoride(F2).The results of ATR-infrared spectroscopic analysis and X-ray photoelectron spectroscopy(XPS) show that it can effectively generate chemical reactions between p-POD fiber and F2.A mass of C—F bonds are formed on the macromolecules of fiber surface and the content of F in the form of —CF/C-O,—CFH and —CF2 is 28.2%,which indicates that there are not only substitution reactions but also addition reactions between p-PODs and F2.The curves of thermal gravimetric analysis(TGA) show that there is not impact on p-POD’s resistance to high temperature,while the aggregative structures of the fluorinated p-POD fiber are more orderly than those of the original fiber from the wide angle X-ray diffraction pattern.In addition,it takes no change in strength of p-POD fiber after fluorination.Under the condition of 20% concentration sulfuric acid which belongs to the artificial accelerated aging test,the retention of strength of fluorinated p-POD fiber remains 84% which increases by about 90% compared to that of the original fiber.Thus,the acid resistance of p-POD is obviously improved owing to the hydrogen bond formed between F atoms and acid solution which makes the protonation of oxadizoles more harder.Besides,there are compact crosslinking layers formed on the surface of p-POD fiber which can slowdown the aging process.