【作者】 白云翔；

【导师】 钱锦文；

【作者基本信息】 浙江大学 ， 高分子化学与物理， 2006， 博士

【摘要】 为提高渗透汽化膜的分离性能、成膜性、热稳定性以及强度等综合性能，共聚物渗透汽化膜材料已开始引起人们的关注。与均聚合物相比较，共聚物具有复杂的链结构和聚集态结构，两者共同决定了共聚物膜的渗透汽化性能。本文从共聚物膜材料的结构和分离性能出发，选择和合成了常温下力学形为不同的共聚物，即橡胶态共聚物HTPB-PU和HTPB-DVB-PU，部分结晶共聚物EVA和玻璃态共聚物PTET-60，制备出相应的渗透汽化分离膜，进而考察各类共聚物膜的结构、渗透汽化性能及其分离机理。1．橡胶态共聚物合成了端羟基聚丁二烯（HTPB）基聚氨酯（脲），（HTPB-PU）并制得相应的渗透汽化膜，用于分离水中微量的乙酸乙酯。实验研究了HTPB数均分子量、料液浓度、料液温度和膜厚对渗透汽化性能的影响。HTPB-PU膜具有很好的优先从水中分离乙酸乙酯的性能，并具有较高的分离因子和通量。DSC研究结果表明，该膜存在两个玻璃化转变温度；透射电镜图像显示明暗相间的微区。可见，该膜具有微相分离结构。表面接触角实验结果显示，成膜时膜的空气接触面比玻璃接触面具有更大的接触角，即空气面更疏水。这归结于疏水的聚丁二烯链段和亲水的氨基甲酸酯（脲）链段分别向空气和玻璃表面迁移的结果。进而，渗透汽化性能结果显示，膜的空气接触面对料液比玻璃接触面对料液具有更高的分离因子和通量。采用疏水性交联剂DVB合成了新型的交联网络膜HTPB-DVB-PU。并制得相应的渗透汽化膜，用于分离水中微量的乙酸乙酯。当料液浓度为2.5wt％时，该膜呈现很强的优先渗透乙酸乙酯的性能，随DVB用量的增加分离因子增加，通量稍微下降。当膜厚为100微米时，分离因子和通量分别可达656和253 g／m²h，均比HTPB-PU膜高。HTPB-DVB-PU膜材料只存在一个T_g，表明HTPB-DVB-PU中的亲水链段没有形成较大的微区。而且膜的空气和玻璃两侧面接触角之差随着DVB含量的增加也逐渐消失，即膜的均一性增加。可见，在HTPB-DVB-PU膜中小的亲水PU相尺寸具有更佳的渗透汽化性能。其分离过程主要由吸附过程控制；膜的密度更小，因而溶涨度比较大，通量高；HTPB-DVB-PU膜的温度敏感性小于HTPB-PU膜。2．结晶态共聚物选用了可部分结晶的EVA共聚物，考察了EVA共聚物的组成和成膜技术对分离水中微量乙酸乙酯性能的影响。发现EVA膜的渗透汽化性能、溶胀行为和膜的聚集行为如结晶度、密度和接触角等与组成密切相关。30℃时，38 wt％VA含量的EVA（EVA38）膜具有最佳的分离性能，分离因子和乙酸乙酯通量分别达118和543 g／m²h。同时，还发现EVA膜的渗透汽化性能，溶胀度和扩散选择性在VA链段含量为38 wt％时都出现转折现象。EVA膜的聚集态结构如结晶度，表面接触角和膜密度随VA含量的变化趋势在EVA38处出也出现转折现象。实验还进一步考察了三种铸膜溶剂，氯仿（CF）、1，2-二氯乙烷（DCE）和环己烷（CYH）对EVA38在溶液中的链形态、本体中聚集态以及对膜的渗透汽化性能影响。研究发现，不仅三种EVA38溶液性质、即特性粘数[η]和相互作用常数K_H不同，而且其本体膜的渗透汽化性能、平衡溶涨度、吸附选择性、广角X射线衍射图和表面接触角等也存在明显差异。提出了由不同选择性溶剂CF、DCE和CYH所得EVA膜呈现不同聚集结构的模型。认为由CF所得EVA38膜中，VA链段和乙烯链段呈无序均一分布的结构，而由DCE和CYH分别所得EVA38膜，分别呈现两种微相分离的核壳结构。并得出了EVA38膜的PV性能与其聚集态结构的关系为，VA链段和乙烯链段都呈无序均一分布结构＞乙烯链段为核VA链段为壳的核壳结构＞VA链段乙烯为壳的的核壳结构。这种聚集态结构的差异随热处理条件增强逐渐减弱。在80℃热处理约12小时后完全消失。3．玻璃态共聚物合成了不同组成的聚对苯二甲酸丙二醇-乙二醇芳香性共缩聚酯（PTET）。广角X射线衍射分析发现当丙二醇含量为60wt％时，即PTET-60为非晶态的无定形共聚物。采用稀溶液粘度法研究了PTET-60和醋酸纤维素（CA）共混物的相容性。发现共混膜中PTET-60含量(W_PTET-60)小于0.35和大于0.5时两者相容，当W_PTET-60在0.35～0.50区间时则不相容。在PTET-60／CA相容区(W_PTET-60≤0.35)内，PTET-60／CA共混物成膜性好，并用于水脱乙酸乙酯分离。纯CA膜是水优先透过膜，但W_PTET-60为0.1的PTET-60／CA共混膜则为乙酸乙酯优先透过膜，而且通量在W_PTET-60为0.25时出现最小值，分离因子出现最大值。总体而言，本文所述共聚物膜用于分离水中微量乙酸乙酯的渗透汽化性能为，橡胶类膜优于部分结晶性膜和玻璃态膜。即，交联网络HTPB-DVB-PU膜＞微相分离HTPB-PU膜＞部分结晶EVA膜＞共缩聚芳香酯共混PTET-60／CA膜。交联网络HTPB-DVB-PU膜分离因子和渗透性（J×d）分别可达656和30300 gμm／m²h。更多还原

【Abstract】 To improve the overall performance of pervaporation （PV） membranes, including separation performance, membrane formation property, heat stability and mechanical strengh and so on, copolymer membrane materials have been paid attention now. Compared with homopolymer, copolymers possess more complicated chain structure and aggregated structure, which determine the separation performance and other properties together. The main aim of this paper was to discuss the aggregated structure of different kinds of copolymers as well as their pervaporation performance and separation mechanism for recovery of trace aroma compounds from their aqueous solutions. So, three kinds of typical copolymers, ie, rubbery copolymer HTPB-PU and HTPB-DVB-PU, semi-crystalline copolymer EVA and glassy copolymer PTET were synthesized or selected as pervaporation membranes respectively.1 .Rubbery copolymer Hydroxyterminated polybutadiene （HTPB）-based polyurethaneurea （PU）,HTPB-PU, was synthesized and firstly used as membrane materials to recover aroma compound, ethyl acetate （EA）, from aqueous solution by PV. The effects of the number average molecular weight （M_n） of HTPB, EA in feed, operating temperature and membrane thickness on the PV performance of HTPB-PU membranes were investigated. The membranes demonstrated high EA permselectivity as well as high EA flux. Two transition temperatures （T_g） were observed from DSC curve and distinct micro phase domain existed in transmission electron micrographs （TEM） of cross sections, which means HTPB-PU membrane had micro-phase separation structure From the results of contact angle measurements, we concluded that the air-side surface is more hydrophobic than that of the glass-sides surface, which were inducedby glass plate and air respectively due to movement of the soft hydrophobic polybutadiene （PB） segments in HTPB-PU chains. Furthermore, the PV performance of the HTPB-PU membrane with the hydrophobic surface facing the feed was much better than that with the hydrophilic surface.A new PV membrane material, HTPB-DVB-PU, was synthesized and the effect of cross-linker DVB content on the pervaporation performance for recovery of EA from its aqueous solution was investigated. When an aqueous solution of 2.5 wt% EA was permeated through the cross-linked HTPB-DVB-PU membranes, they showed a high EA permselectivity and permeability of these membranes was enhanced with increasing DVB content significantly. The best permeation rate and separation factor of HTPB-DVB-PU membrane were 253 g/m²h and 656 respectively with membrane thickness of about 100 μm. Only one T_g can be observed from DSC curve, which means the hard segments did not form bigger micro domain in HTPB-DVB-PU. Furthermore, with the increasing DVB content the differnce of PV performance between the two sides of the membrane disspeared, that is, the membrane became more homogeneous. In conclusion, the smaller dimension of hard segments micro domain led to a better PV performance. Compared with HTPB-PU membrane, the separation process was mainly governed by sorption process.and the density of HTPB-DVB-PU membrane was smaller, so the degree of swelling （DS） and the total flux were larger. HTPB-DVB-PU membrane had low heat sensitivity than HTPB-PU membrane. 2.Crystalline copolymerAggregated behavior and pervaporation characterization of ethylene-vinyl acetate （EVA） copolymer membranes with different vinyl acetate （VA） cotent from 26 （EVA26） to 100 （EVA100） wt% for recovery of ethyl acetate （EA） from water were investigated. The pervaporation （PV） characterization, such as separation factor, EAflux, diffusion selectivity, and the swelling behavior of EVA membranes with VA content displayed a turning phenomena at 38 wt% VA content. Aggregated behavior of the crystallization degree, the bulk density and contact angle of EVA membranes with VA content were also turned at 38 wt% VA content. The PV characterization and the swelling behavior of EVA membranes with different VA contents could be explained in terms of the aggregated behavior of the EVA copolymer.The solution property [η] and K_H of EVA copolymer with 38 wt% VA content in selective solvents of chloroform （CF）, 1, 2-dichloroethane （DCE） and cyclohexane （CYH） and the bulk properties the swelling degree at equlibrium, sorption selectivity, contant angle and crystalinity of EVA membranes cast in selective solvents above were measured by an Ubbelohode viscometer, swelling, sorption, contact angle and wide-angle X-ray diffraction （WAXD） experiments respectively. It was drawn that the solution structures of the EVA and the aggregated structures of its membrane were quite different, i.e., displaying a random homogeneous structure, a core-shell structure with the shell of VA sequences and a core-shell structure with the shell of ethylene sequences, due to different selective solvents, CF, DCE and CYH used respectively. The pervaporation performance of the EVA membrane with 38 wt% VA content increased with the aggregated structures of its membrane, the core-shell structure with the shell of ethylene sequences, the core-shell structure with the shell of VA sequences and the random homogeneous structure in order. These aggregated structures disappeared basically after the EVA membranes annealed for 12 hours at 80℃. 3.Glassy copolymerAromatic copolyester of poly（trimethylene-co-ethylene terephthalate） （PTET） with different composition was synthesized and the PTET sample with 60 percent weight fraction of polytrimethylene （PTET-60） was amorphous. The compatibility of PTET-60/cellose acetate （CA） blends and the pervaporation of their membranes forseparation of EA/water mixtures were investigated. It was found that PTET-60 is compatible with CA when the weight fraction of PTET-60 (W_PTET-60) in PTET-60/CA blends is lower than 0.35 and more than 0.5. In the region of compatibility (W_PTET-60≤ 0.35), the PTET-60/CA blend membrane showed good film-forming property. So , we prepared PTET-60/CA blend membrane with W_PTET-60≤0.35 for separation EA from water. The pure CA membrane showed water selective, while EA could preferentially permeat through PTET-60/CA blend membrane and both the maximum value of total flux and minimum value of the separation factor existed at W_PTET-60= 0.25.As a whole, in our study the PV performance of the rubbery copolymers for recovery of EA from aqueous solution is better than that of semi-crystilline copolymer and glassy copolymer, ie, HTPB-DVB-PU>HTPB-PU>EVA > PTET-60/CA, and the separation factor and the permeability of HTPB-DVB-PU membrane reached 656 and 30300 gμm/m²h, respectively更多还原