【作者】 赵峰；

【导师】 唐建国；

【作者基本信息】 青岛大学 ， 材料加工工程， 2008， 硕士

【摘要】 聚偏氟乙烯(PVDF)和聚四氟乙烯(PTFE)材料具有优良的化学稳定性和机械性能,能耐热、耐寒、耐辐射和耐化学腐蚀,长期以来作为优良的膜材料广泛应用于工业生产当中,但二者均有极强的疏水性,应用过程中容易造成污染,造成水通量和分离效率下降,要制备pH值敏感型微孔膜需要对其进行改性,提高其亲水性。本文采用表面化学接枝改性的方法制备pH值敏感型含氟微孔膜。相对于膜表面处理法改进膜的亲水性,接枝法使膜能得到持久稳定的亲水性;相对于其他接枝改性方法,化学法不需特殊设备,成本更加低廉,而且可以连续生产,适合大型工业化生产的需求。先分别用强碱、强氧化剂溶液和萘钠溶液对PVDF和PTFE进行脱氟预处理,在膜表面引入双键和羟基、羧基等极性基团,然后用硝酸铈铵引发剂以这些极性基团为活性点引发甲基丙烯酸(MAA)的接枝反应。详细考察了预处理时间、接枝反应时间、接枝单体的浓度对接枝率的影响,通过研究接枝率对pH值敏感性和膜机械性能的影响,确定了制备性能优良的pH值敏感型含氟聚合物膜的适宜反应条件。通过全反射傅立叶变换红外光谱和X射线能谱分析改性前后膜表面化学成分的变化证实膜表面确实有聚甲基丙烯酸接枝层存在。经扫描电子显微镜和原子力显微镜对改性前后膜表面形貌的观察表明,接枝膜表面孔数减少,孔径变小,并且观察到孔内有絮状物,进一步证明接枝甲基丙烯酸的存在。甲基丙烯酸的pKa=5.65,在pH=4和pH=7的条件下对接枝改性膜进行水通量测试,PVDF-g-PMAA和PTFE-g-PMAA改性膜都表现出良好的pH值敏感性。当PVDF-g-PMAA改性膜的接枝率在3%-6.1%的范围内时改性膜的水通量大于原膜,并且对pH值的响应性最好。而对于PTFE-g-PMAA改性膜,综合考虑PTFE改性膜的机械性能和pH值敏感性的需要,将接枝率控制在5%～6%以内改性效果最好。更多还原

【Abstract】 Polyvinylidene fluoride (PVDF) and poly(tetrafluoroethylene) (PTFE) possess excellent chemical stability and mechanical properties, they has good resistant to heat, cold, radiation and chemical corrosion and widely used as excellent membrane materials in industry for a long time, but they both have strong hydrophobicity which can cause the pollution of the membranes. These will decrease the permeate flux and separation efficiency. In order to prepare pH sensitive microporous membrane, we need to modify their hydrophilicity.In this thesis, we adopt surface chemical grafted method to prepare fluoride pH sensitive microporous membrane. In contrast with surface treating method, surface grafting method can provide a more steady and durable hydrophilicity; In contrast with other grafting methods, chemical grafting method don’t need special equipments so more low-cost to be suitable for the industrial continues producing.First PVDF membranes were pretreated by strong alkaline solution of potassium permanganate and PTFE membranes were pretreated by sodium naphthalene solution, the pretreatment process can introduce some double bonds, hydroxide groups, carboxyl groups to the surface of the membrane. Then the pH sensitive membrane were prepared by grafting poly(methacrylic acid) (PMAA) from these active points using cetric ammonium nitra (CAN) as initiator. Through studying the infection of reaction conditions to the grafting ratio, appropriate reaction conditions were made based on the infection of grafting ratio to the pH sensitive ability and mechanical properties.It was proved that the PMAA grafting layer exists on the surface of the membrane through studying the surface compositions of the virgin and modified membrane were determined by FT-IR and EDS. Further more, SEM and AFM test showed that the number of pores of decreased, and the diameter of the pores minished and floccules were observed in the pores, which were the further evidence of the existence of PMMA. Since the pKa value of PMMA is 5.65, so flux test was carried our under pH=4 and pH=7. As a result, PVDF-g-PMAA and PTFE-g-PMAA showed excellent pH sensitive property. Considered all the infections, the best grafting ratio of PVDF-g-PMAA is 3%～6.1% and the best grafting ratio of PTFE-g-PMAA is 5%～6%.更多还原