【作者】 刘鸣；

【导师】 郭玉海；

【作者基本信息】 浙江理工大学 ， 材料学， 2010， 硕士

【摘要】 利用膜对颗粒的吸附、截留和筛分作用进行分离的微滤技术得到迅速发展。在众多的膜材料中,聚四氟乙烯（PTFE）微孔薄膜由于其耐酸、耐碱、耐高温、微孔结构可调控性强等优点,被广泛应用于环保、过滤、纺织、医疗、军事等方面。但由于PTFE表面能低,表面润湿性差,影响了其在过滤领域的应用,因此薄膜的亲水改性成为研究热点。本文在深入分析包括钠-萘化学处理等在内的传统化学改性对材料本体性能影响大的基础上,提出了物理改性的思路。依赖分子间作用力在PTFE微孔膜表面吸附沉积Fe³⁺,再在沉积层上聚合亲水性单体并形成配位键合,在基本不影响薄膜本体性能的前提下,对PTFE微孔膜进行物理亲水改性。通过FTIR、SEM、ζ电位分析、超声振荡、接触角、水通量等手段研究了改性薄膜的结构和性能。结果表明,PTFE薄膜的亲水性能得到了显著的提高。主要研究内容和结论:（1）超声振荡和FTIR实验表明,Fe（OH）₃胶体可牢度地吸附在PTFE膜上,二者之间通过分子间作用力结合。吸附降低了薄膜与水的接触角,提高了表面张力。最佳吸附条件为:浸渍液为,20mL沸水/FeCl₃溶液（1mol/L）7.5mL/NaOH溶液（2mol/L）1.5mL;浸渍时间20h、浸渍温度15℃。（2）依据电负性及离子半径对溶液离子特性与吸附作用进行理论分析,通过ζ电位测试MgCl₂和CuCl₂等溶液进行理论验证,认为由于Fe³⁺具有大的电负性以及比H⁺的离子半径大的特点,赋予了PTFE与Fe³⁺之间较强的亲合力;与Cu（OH）₂比较,水解能力强的Fe3+容易形成胶体,可牢固吸附到PTFE薄膜上。（3）为了进一步提高Fe（OH）₃胶体吸附后PTFE薄膜的亲水性能,再聚合丙烯酸（AA）亲水性单体。采用FTIR分析了聚丙烯酸（PAA）与Fe（OH）3之间的键合作用,认为PAA与Fe（OH）₃通过桥式配位相连接。（4）实验研究了单体AA浓度、引发剂（NH₄）₂S₂O₈用量、聚合温度和时间等对薄膜增重率的影响,建立了膜增重率与水通量间的关系。最佳聚合条件为:AA浓度25%,（NH₄）₂S₂O₈用量1%（占单体重量）,聚合温度60℃,聚合时间60min。此时薄膜增重率为7.9%,薄膜与水的接触角由146°降至76°,表面张力由1.15×10^-2N·m^-1增大到5.92×10^-2N·m^-1,水通量从0增大至0.069 m³·m^-2·h^-1,薄膜的亲水改性效果显著,水透过性能得到改善。该方法不仅拓宽了PTFE薄膜亲水改性途径,而且为有机与无机材料相结合提供了新的加工方法。更多还原

【Abstract】 The use of membrane on particle adsorption, retention and separation by microfiltration technology has been developing rapidly. Among the membrane materials, PTFE microporous membrane due to its acid and alkali resistance, high temperature resistance, strong regulation of pore structure has been widely used in environmental protection, filtration, textile, medical, military and so on. However, because of extremely low surface energy and strong hydrophobicity, PTFE’s application in aqueous filtration is still limited. So, studies on the hydrophilic modification of PTFE membrane become necessary.Traditional chemical modification including sodium-naphthalene chemical treatment can damage PTFE material itself. This paper, after analyzing the influence of chemical treatment on PTFE, put forward an idea of physical modification.The method of physical modification was as follows: firstly, Fe³⁺ were adsorbed and deposited on the surface of PTFE microporous membrane, then according to the theory of coordination bonding, hydrophilic monomer were polymerized on PTFE membrane which had adsorbed Fe³⁺. This method of physical hydrophilic modification on PTFE microporous membrane did not affect the performance of membrane itself on the whole. The structure and properties of modified membrane were studied by means of FTIR, SEM,ζpotential, ultrasonic oscillation, contact angle, water flux and so on. The results showed that the hydrophilic performance of PTFE membrane was improved significantly.The main contents and conclusions in research are as follows:（1） The ultrasonic oscillation and FTIR results showed that Fe（OH）₃ colloid can be adsorbed on the PTFE membrane stably. The Fe（OH）₃ and PTFE membrane were interacted through intermolecular forces. The contact angle of water on the membrane was decreased and the surface tension was increased after Fe（OH）₃ adsorption. The best conditions of adsorption were as fellows: dipping solution,20mL boiling water /FeCl3 Solution（1mol/L）7.5mL /NaOH Solution（2mol/L）1.5mL; dipping time 20h, and dipping temperature 15℃。（2） Ionic characteristics and adsorption were theoretically analyzed based on electronegativity and ionic radius, which was validated byζpotential test of PTFE membrane in MgCl₂ solution, CuCl₂, FeCl₃ solution and so on. The results showed that PTFE and Fe³⁺ had a special affinity, which was derived from the larger electronegativity of Fe³⁺ than other metal ions’and the larger ionic radius of Fe³⁺ than H⁺’s. Besides, in comparison with Cu（OH）₂, Fe³⁺ has a strong tendency of hydrolysis and becomes colloid easily, it can absorb onto the PTFE membrane stably.（3） In order to further enhance the membrane hydrophilicity which had adsorbed Fe（OH）₃ colloid, the membrane was further put into acrylic acid （AA） aqueous solution and acrylic acid polymerization was carried out. The structure of polyacrylic acid （PAA） and Fe（OH）₃ was analyzed by FTIR, the results showed that the connection between PAA and Fe（OH）₃ were dependent on bridge coordination. （4） In this paper, the factors influencing the weight gain ratio of polyacrylic acid onto the PTFE membrane had been studied, and the relationship between membrane weight gain ratio and water flux had been established. The best conditions of polymerization were as fellows: 25% AA monomer concentration, 1% （NH₄）₂S₂O₈ （initiator） of the total monomer weight, polymerization temperature 60℃, polymerization time 60min. Under the best conditions of polymerization, membrane weight gain ratio was 7.9%, the contact angle of water on the membrane was decreased from 146°to 76°, the surface tension was increased from 1.15×10^-2N·m^-1 to 5.92×10^-2N·m^-1, the water flux was increased from 0 to 0.069 m³·m^-2·h^-1. The effect of hydrophilic modification was obvious, and the performance of water permeation through the membrane was improved significantly. The method put forward in this paper not only broadens the ways of hydrophilic modification on PTFE, but also provides a new processing method by combination of organic and inorganic materials.更多还原