中空纤维膜的表面结构调控及性能研究

发布时间：2018-04-12 11:36

本文选题：紫外辐照 + 羟基丙烯酸酯　；参考：《天津工业大学》2016年博士论文

【摘要】：聚砜(PSF)、聚丙烯(PP)等是常见的有机聚合物膜材料,但由于它们具有较强的疏水性,在应用过程中极易被污染,造成膜通量的衰减、膜利用率和膜寿命的降低以及膜应用成本的增高,因此开发新型亲水性膜或对现有膜材料进行亲水改性具有重要理论意义和实用价值。紫外辐照法具有反应条件温和、工艺简单、波长连续可调节且反应只能在材料表面发生等优点,是一种常用的表面改性方法。为解决常见的有机聚合物膜易污染的问题,本文采用紫外光辐照接枝法,分别通过添加光敏剂与否、改变单体的相对分子质量大小及调整单体的亲水性官能团的数目和分布对中空纤维膜的表面结构进行调控,并对其性能进行表征。优化中空纤维膜表面改性方法,制备出亲水性和抗污染性良好的中空纤维膜。本文的具体研究内容和结论如下：首先,采用间歇式紫外辐照法,以聚砜和聚丙烯中空纤维膜为探针,以丙烯酸(AA)和丙烯酸羟乙酯(HEA)为单体,研究光敏剂存在与否对膜表面结构及性能的影响。结果表明,光敏剂存在与否对膜表面结构有较大影响。无光敏剂时,经紫外辐照后聚砜中空纤维膜表面虽有亲水性单体成功接枝,但聚砜膜基体结构受到损伤,表面孔结构增大,改性膜的截留率降低,而聚丙烯膜表面基本没有发现单体的接枝；存在光敏剂时,紫外辐照后,聚砜和聚丙烯中空纤维膜表面均有单体成功接枝,膜表面结构得到调控,改善了膜的亲水性和抗污染性。其次,采用间歇式紫外辐照法,以PSF中空纤维膜为探针,以自制的丙烯酸羟乙酯(HEA)、丙烯酸羟丙酯(3HPA)、丙烯酸丁二醇单酯(4HBA)和丙烯酸三羟甲基丙烷单酯(TMPAA)四种不同的羟基丙烯酸酯为单体,研究了单体的相对分子质量大小对膜表面结构及性能的影响。结果表明,经过紫外辐照后,几种单体均能够在膜表面成功接枝,均能在膜表面上引入亲水性的羟基官能团,使膜表面结构发生改变,并使膜的亲水性和抗污染性得到提高。相同条件下,羟基丙烯酸酯的相对分子质量越大,分子的碳链越长,其在膜表面的接枝密度越低,引入膜表面的羟基密度越小,其对膜亲水性及抗污染性的提高程度也越小；但适当地增加功能单体中亲水性官能团羟基的数目可以增大膜表面的羟基含量,进而可以有效地改善膜表面的亲水性和抗污染性。当TMPAA在PSF膜上的接枝密度为3.02 mmol.m-2时,膜的外表面接触角由原膜的80°降低到改性膜的46°,纯水通量由原膜的115 L.m-2.h-1增加到改性膜的173 L.m-2.h-1,对BSA的截留率由88.6%增加到93.4%,过滤BSA溶液的通量衰减率由66.4%降低到26.9%,清洗后PSF-g-TMPAA膜的通量恢复率也由68.6%增加到90.5%。此外,为进一步实现工业化,提高实际应用价值,采用连续化紫外辐照法,以PP中空纤维膜为探针,以自制的丙烯酸羟乙酯(HEA)、丙烯酸甘油单酯(GA)和丙烯酸季戊四醇单酯(PEA)三种不同的羟基丙烯酸酯为单体,研究了羟基的数目和分布对膜表面结构及性能的影响。研究发现,使用不同单体时,可以得到不同羟基数目和分布的聚丙烯中空纤维改性膜,有效改善膜表面的化学结构和形貌。另外,通过使用不同单体对改性膜表面进行结构设计,可以显著增加膜表面的亲水性和抗污染性。相同条件下,膜表面的亲水性和抗污染性随着引入膜表面的羟基数目的增加而增强；而羟基分布的影响相对复杂,接枝密度较低时,羟基分布越集中,膜表面的亲水性和抗污染性越好,接枝密度较高时,羟基分布对膜性能的影响不明显。当PEA在PP中空纤维膜上的接枝密度为0.838 mmol.m-2时,膜表面的亲水性和抗污染性得到显著改善,改性膜表面的水滴仅需6.3 s就完全消失,PP-g-PEA膜的纯水通量大约增加到原膜纯水通量的4.5倍,膜的通量衰减由原膜的56%下降为改性膜的21%,清洗后的膜的通量恢复率由原膜的34%增加到改性膜的85%。本文的研究表明,通过添加光敏剂条件下亲水性功能单体在膜表面的紫外辐照接枝聚合,可以实现膜表面结构的调控,在膜表面引入亲水性官能团的同时不损伤膜基体结构,能够有效提高膜表面的亲水性和抗污染性。另外,可以通过改变功能单体的相对分子质量大小以及亲水性官能团数目和分布对膜表面结构进行有效调控,本文的研究为亲水性膜的表面结构设计提供了一定的理论基础,对新型亲水膜的制备具有指导意义。
[Abstract]:Polysulfone (PSF), polypropylene (PP) is a common organic polymer film materials, but because they have strong hydrophobicity, can easily be contaminated in the application process, causes attenuation of membrane flux increased, and reduce the rate of membrane life and membrane application cost by membrane, so the development of a new type of hydrophilic membrane or it has important theoretical significance and practical value of hydrophilic modification of existing membrane materials. Ultraviolet irradiation method has mild reaction condition, simple process, can be adjusted and the advantages of wavelength continuous reaction only on the surface of the material occurs, is a commonly used method of surface modification of organic polymer film. In order to solve the common problems of pollution. This paper adopts UV irradiation grafting method, respectively, by adding photosensitizer or not, change the number of molecular weight and adjusting the monomer hydrophilic functional groups and the distribution of surface structures of hollow fiber membrane. For regulation, and its properties were characterized. The optimization of membrane surface modification method, preparation of hollow fiber membrane hydrophilicity and anti pollution well. The specific contents and conclusions are as follows: first, the use of intermittent UV irradiation method, using polysulfone and polypropylene hollow fiber membrane as a probe to acrylic acid (AA) and 2-hydroxyethyl acrylate (HEA) as the monomer, the existence of photosensitizer on the structure and properties of the film surface is investigated. The results show that the existence of photosensitizer on the membrane surface structure has great influence. Without photosensitizer, after ultraviolet irradiation of polysulfone hollow fiber membrane surface is hydrophilic monomer the successful grafting, but the polysulfone membrane matrix structure damage, increase the surface pore structure, the modified membrane interception rate decreased, and the polypropylene membrane has uncovered graft monomer; existence of photosensitizer, ultraviolet irradiation, and poly sulfone hollow polypropylene Fiber membrane surface of both monomers were grafted, membrane surface structure control, improve the membrane hydrophilicity and anti fouling properties. Secondly, using intermittent UV irradiation, the PSF hollow fiber membrane as a probe to hea - (HEA), hydroxypropyl acrylate (3HPA), butyl glycol monoester (4HBA) and acrylic acid three trimethylolpropane ester (TMPAA) four different hydroxyl acrylate as monomer, studied the effect of molecular weight of monomer on the structure and properties of the membrane surface. The results showed that after UV irradiation, several monomers were successfully grafted on the surface of the film can be that can introduce hydrophilic hydroxyl groups on the membrane surface, the membrane structure changed, and the membrane hydrophilicity and antifouling properties were improved. Under the same conditions, the relative molecular mass of hydroxyl acrylate larger molecules with longer carbon chain on the membrane surface, the The grafting density is low, the membrane surface hydroxyl density is small, the membrane hydrophilicity and anti fouling properties improved degree is smaller; but due to increasing the number of hydroxyl content of hydroxyl functional monomer in hydrophilic functional groups can increase the membrane surface, which can effectively improve the surface hydrophilicity and anti pollution. When the grafting density of TMPAA on PSF film is 3.02 mmol.m-2, the outer membrane surface contact angle from the original film 80 degrees down to 46 degrees of the modified membrane, pure water flux increased from 115 L.m-2.h-1 to the original film modified film 173 L.m-2.h-1, the retention of BSA increased by 88.6% 93.4%, the filtration of BSA solution flux decay rate decreased from 66.4% to 26.9%, after cleaning the PSF-g-TMPAA membrane flux recovery rate also increased from 68.6% to 90.5%., in addition, to further realize the industrialization, improve the practical application value, with the continuous ultraviolet irradiation method, PP hollow fiber Fiber membrane probe with ethyl acrylate (HEA), a self-made acrylic acid monoglyceride (GA) and acrylic acid pentaerythritol monoester (PEA) three different hydroxyl acrylate monomers on the hydroxyl number and distribution effects on the structure and properties of the membrane surface. The study found that the use of different monomers that can get the number and distribution of polypropylene hollow fiber membrane modified by hydroxyl groups, the chemical structure and morphology can effectively improve the membrane surface. In addition, the paper designs the structure of the modified membrane surface using different monomers, can significantly increase the membrane surface hydrophilicity and anti fouling properties. Under the same condition, the surface hydrophilic membrane and pollution resistance increases with the introduction of surface hydroxyl substituents increased; and the effect of hydroxyl distribution is relatively complex, lower grafting density, hydroxyl distribution is concentrated, the membrane surface hydrophilicity and antifouling properties better, grafting density When high hydroxyl distribution effects on membrane properties is not obvious. When the grafting density of PEA in the PP hollow fiber membrane was 0.838 mmol.m-2, the membrane surface hydrophilicity and anti fouling resistance are significantly improved, the modified membrane surface water is only 6.3 s completely disappeared, pure water flux increased about PP-g-PEA film to 4.5 times the original water flux of membrane, the membrane flux attenuation decline for the modified film 21% by the original film 56%, after cleaning the membrane flux recovery rate increased from 34% to the original film of modified 85%. film in this paper showed that the hydrophilic functional monomer adding photosensitizer conditions in ultraviolet polymerization graft polymerization of the membrane surface, may regulate membrane surface structure, the introduction of hydrophilic functional groups on the membrane surface without damaging the substrate structure, can effectively improve the surface hydrophilicity and anti fouling properties. In addition, by changing the relative points of functional monomer The size and distribution of the hydrophilic functional groups can effectively control the surface structure of the membrane. This study provides a theoretical basis for the design of the surface structure of the hydrophilic membrane, and has a guiding significance for the preparation of the new hydrophilic membrane.

【学位授予单位】：天津工业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TQ051.893

【参考文献】