復(fù)合熱致相分離法制備PVDF共混膜的研究
發(fā)布時(shí)間：2018-09-14 11:31
【摘要】：聚偏氟乙烯(PVDF)作為分離膜的常用材料,廣泛應(yīng)用于給水工程、工業(yè)廢水、醫(yī)藥行業(yè)、食品行業(yè)、能源行業(yè)等領(lǐng)域。但PVDF膜的強(qiáng)疏水性,導(dǎo)致其易于被污染,增加膜的運(yùn)行成本,限制了其使用。制備PVDF膜多采用相轉(zhuǎn)化法,其主要包括:非溶劑致相分離法(NIPS)、熱致相分離法(TIPS)、復(fù)合熱致相分離法(NTIPS)等。本文在系統(tǒng)研究PVDF膜的制備方法的基礎(chǔ)上,采用了共混改性的方法對(duì)PVDF膜改性,利用NTIPS法制備了性能優(yōu)良、親水性強(qiáng)、非對(duì)稱結(jié)構(gòu)的PVDF共混膜。首先,利用流變儀考察了PVDF與己內(nèi)酰胺(CPL)二元體系的流變性能,研究了PVDF百分含量、剪切速率、制膜溫度等對(duì)PVDF/CPL鑄膜液體系的影響。結(jié)果表明,PVDF/CPL鑄膜液體系為非牛頓性流體。隨著PVDF質(zhì)量百分含量的增加,粘流活化能增加,非牛頓性指數(shù)減小。PVDF質(zhì)量百分含量高的鑄膜液體系,剪切頻率對(duì)體系的影響較小,溫度對(duì)其的靈敏度高,制膜過程對(duì)溫度的控制需要更加精確。PVDF質(zhì)量百分含量低的鑄膜液體系,受剪切頻率的影響較大,溫度對(duì)其的靈敏度低。此研究為制備PVDF膜的工藝選定,提供了參考。其次,本文以CPL為稀釋劑,PVDF與親水性聚合物共混,采用NTIPS法制備PVDF共混膜。采用DSC法考察了親水的聚合物與PVDF之間的相容性。利用掃描電鏡分析PVDF共混膜的不同結(jié)構(gòu)。通過對(duì)膜接觸角的考察,進(jìn)而分析膜的親水性。分別考察了膜材料濃度、共混比例、凝固浴溫度不同對(duì)膜的結(jié)構(gòu)與性能的影響。研究表明,聚氧化乙烯(PEO)與聚乙烯醇(PVA)對(duì)PVDF膜的親水改性效果較好,聚甲基丙烯酸甲酯(PMMA)親水改性效果不明顯。當(dāng)高分子膜材料的濃度增加時(shí),PVDF共混膜的膜孔徑、孔隙率變小,膜的水通量降低,而膜的截留率升高。PVDF與親水聚合物的不同比例也調(diào)控著膜的結(jié)構(gòu)與性能。當(dāng)PMMA含量增加,影響PVDF結(jié)晶,形成不同的支撐層結(jié)構(gòu)。當(dāng)PVDF與PEO共混比增加到8:2,由于PEO分子量大,與PVDF存在微觀相分離,形成不同結(jié)構(gòu)的皮層。當(dāng)PVA含量的增加,傳質(zhì)加快,形成海綿狀結(jié)構(gòu),同時(shí),膜的親水性能加強(qiáng)。凝固浴溫度對(duì)NTIPS法制得膜的結(jié)構(gòu)影響較大。隨著凝固浴溫度的升高,NTIPS法制備的PVDF共混膜,NIPS成膜過程占主導(dǎo),導(dǎo)致大孔結(jié)構(gòu)增加。最后,分別理論計(jì)算了PVDF/PMMA、PVDF/PEO、PVDF/PVA共混膜阻力分布�？疾旃不炷さ哪臀廴拘阅�,并進(jìn)一步考察清洗、恢復(fù)效果。結(jié)果顯示,PVDF/PEO與PVDF/PVA共混改性膜的耐污染性能提高,清洗效果較好。
[Abstract]:Polyvinylidene fluoride (PVDF) is widely used in water supply engineering, industrial wastewater, pharmaceutical industry, food industry, energy industry and so on. However, the strong hydrophobicity of PVDF membrane makes it easy to be polluted, increases the running cost of the membrane, and limits its use. PVDF films are prepared by phase inversion method, including non-solvent induced phase separation method, (NIPS), thermal phase separation method, (TIPS), composite thermal phase separation method, (NTIPS) method and so on. On the basis of systematically studying the preparation method of PVDF membrane, the PVDF membrane was modified by blending method. The PVDF blend membrane with excellent properties, strong hydrophilicity and asymmetric structure was prepared by NTIPS method. Firstly, the rheological properties of binary systems of PVDF and caprolactam (CPL) were investigated by rheometer. The effects of the content of PVDF, shear rate and film preparation temperature on the casting solution of PVDF/CPL were studied. The results show that PVDF / CPL casting liquid system is a non Newtonian fluid. With the increase of mass percent content of PVDF, the viscous flow activation energy increases, and the non-Newtonian index decreases. The control of temperature in the process of film preparation requires a more accurate casting liquid system with low mass percent content of PVDF, which is greatly affected by shear frequency and has low sensitivity to temperature. This study provides a reference for the process selection of PVDF films. Secondly, the PVDF blend membrane was prepared by NTIPS method with CPL as diluent and hydrophilic polymer. The compatibility between hydrophilic polymer and PVDF was investigated by DSC method. The different structure of PVDF blend membrane was analyzed by SEM. The hydrophilicity of the membrane was analyzed by investigating the contact angle of the membrane. The effects of membrane material concentration, blending ratio and coagulation bath temperature on the structure and properties of the membrane were investigated. The results showed that the hydrophilic modification effect of polyvinyl peroxide (PEO) and polyvinyl alcohol (PVA) on PVDF membrane was better than that of poly (methyl methacrylate) (PMMA). When the concentration of polymer membrane material increases, the pore size of PVDF blend membrane becomes smaller, the water flux of membrane decreases, and the membrane rejection increases. The different ratio of PVDF and hydrophilic polymer also regulates the structure and properties of the membrane. When the content of PMMA increases, the crystallization of PVDF is affected and different supporting layer structures are formed. When the blending ratio of PVDF and PEO is increased to 8: 2, because of the large molecular weight of PEO, there is a microcosmic phase separation from PVDF to form different structures of cortex. With the increase of PVA content, mass transfer accelerates, forming spongy structure, and the hydrophilicity of the membrane is enhanced. The solidification bath temperature has a great influence on the structure of NTIPS film. With the increase of coagulation bath temperature, the film forming process of PVDF blend membrane is dominant, which leads to the increase of macroporous structure. Finally, the resistance distribution of PVDF/PMMA,PVDF/PEO,PVDF/PVA blend membrane was calculated theoretically. The fouling resistance of the blend membrane was investigated, and the cleaning and recovery effects were further investigated. The results showed that the PVDF / PEO / PVDF/PVA blend modified membrane had better cleaning performance and better pollution resistance.
【學(xué)位授予單位】：寧波大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TQ051.893
本文編號(hào)：2242587
[Abstract]:Polyvinylidene fluoride (PVDF) is widely used in water supply engineering, industrial wastewater, pharmaceutical industry, food industry, energy industry and so on. However, the strong hydrophobicity of PVDF membrane makes it easy to be polluted, increases the running cost of the membrane, and limits its use. PVDF films are prepared by phase inversion method, including non-solvent induced phase separation method, (NIPS), thermal phase separation method, (TIPS), composite thermal phase separation method, (NTIPS) method and so on. On the basis of systematically studying the preparation method of PVDF membrane, the PVDF membrane was modified by blending method. The PVDF blend membrane with excellent properties, strong hydrophilicity and asymmetric structure was prepared by NTIPS method. Firstly, the rheological properties of binary systems of PVDF and caprolactam (CPL) were investigated by rheometer. The effects of the content of PVDF, shear rate and film preparation temperature on the casting solution of PVDF/CPL were studied. The results show that PVDF / CPL casting liquid system is a non Newtonian fluid. With the increase of mass percent content of PVDF, the viscous flow activation energy increases, and the non-Newtonian index decreases. The control of temperature in the process of film preparation requires a more accurate casting liquid system with low mass percent content of PVDF, which is greatly affected by shear frequency and has low sensitivity to temperature. This study provides a reference for the process selection of PVDF films. Secondly, the PVDF blend membrane was prepared by NTIPS method with CPL as diluent and hydrophilic polymer. The compatibility between hydrophilic polymer and PVDF was investigated by DSC method. The different structure of PVDF blend membrane was analyzed by SEM. The hydrophilicity of the membrane was analyzed by investigating the contact angle of the membrane. The effects of membrane material concentration, blending ratio and coagulation bath temperature on the structure and properties of the membrane were investigated. The results showed that the hydrophilic modification effect of polyvinyl peroxide (PEO) and polyvinyl alcohol (PVA) on PVDF membrane was better than that of poly (methyl methacrylate) (PMMA). When the concentration of polymer membrane material increases, the pore size of PVDF blend membrane becomes smaller, the water flux of membrane decreases, and the membrane rejection increases. The different ratio of PVDF and hydrophilic polymer also regulates the structure and properties of the membrane. When the content of PMMA increases, the crystallization of PVDF is affected and different supporting layer structures are formed. When the blending ratio of PVDF and PEO is increased to 8: 2, because of the large molecular weight of PEO, there is a microcosmic phase separation from PVDF to form different structures of cortex. With the increase of PVA content, mass transfer accelerates, forming spongy structure, and the hydrophilicity of the membrane is enhanced. The solidification bath temperature has a great influence on the structure of NTIPS film. With the increase of coagulation bath temperature, the film forming process of PVDF blend membrane is dominant, which leads to the increase of macroporous structure. Finally, the resistance distribution of PVDF/PMMA,PVDF/PEO,PVDF/PVA blend membrane was calculated theoretically. The fouling resistance of the blend membrane was investigated, and the cleaning and recovery effects were further investigated. The results showed that the PVDF / PEO / PVDF/PVA blend modified membrane had better cleaning performance and better pollution resistance.
【學(xué)位授予單位】：寧波大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TQ051.893
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