聚合物分子量对热致相分离法制备聚乙烯微孔滤膜的影响

选取不同分子量的聚乙烯/二苯醚作为聚合物稀释剂体系,通过浊点及结晶温度绘制了体系的热力学相图;并在不同淬冷温度下,通过热致相分离法制备了聚乙烯微孔滤膜。讨论了聚合物分子量及淬冷温度对成膜孔结构的影响。结果表明:聚合物的分子量不仅影响微孔滤膜断面的孔径,还影响其形态和结构。     

动力学因素对热诱导相分离法制备亲水性乙烯-丙烯酸共聚物微孔膜结构的影响

选择 3种不同丙烯酸含量的乙烯 丙烯酸共聚物 (EAA)为原材料 ,二苯醚 (DPE)为稀释剂 ,研究了淬冷温度、粗化时间等影响液滴生长的动力学因素对热诱导相分离法 (TIPS)制备EAA DPE亲水性高分子微孔膜结构的影响 .淬冷温度的高低决定了EAA DPE体系是发生液 液相分离还是固 液相分离 ,而产生相分离的机理不同将影响稀释剂液滴的生长 ,最终影响微孔膜的孔径 .实验结果表明 ,在相同粗化时间的条件下 ,随着EAA1 41 0 DPE、EAA3 0 0 2 DPE、EAA3 0 0 3 DPE三体系冷却温度的逐渐升高 ,孔径逐渐变大 .在结晶温度以下 ( 0℃、3 0℃、60℃ )粗化时间相同时 ,温度对微孔膜的孔径影响较小 ,例如 0℃和 3 0℃的恒温条件粗化 1 0min,微孔膜的孔径在 1～ 3 μm之间 ;在 60℃的恒温条件粗化 1 0min ,微孔膜的孔径在 3～ 5 μm之间 .而在 90℃的恒温条件粗化相同的时间 ,由于体系始终处于结晶温度线以上 ,体系始终处在液 液相分离区域 ,最终得到微孔膜的孔径达到了 6～8μm .在结晶温度以下 ( 3 0℃ )进行恒温粗化 ,由于体系的过冷程度很大 ,液滴相的粗化过程被抑制住 ,所以粗化时间对微孔膜的孔径影响不大 ;而在结晶温度以上 ( 90℃ )进行恒温粗化时 ,则是随着粗化时间的延长 ,微孔膜的孔径逐渐变大     

热致相分离法制备聚苯硫醚微孔膜

采用热致相分离法,以己内酰胺为溶剂,制备得到了聚苯硫醚微孔膜并对薄膜性能表征.聚苯硫醚-己内酰胺体系制膜的优点之一是溶剂己内酰胺是水溶性的,可以采用纯水作为后处理的萃取剂.选择了合适的浓度,利用压制成型法制备聚苯硫醚平板膜;研究了体系冷却时的相行为,并考察了降温速率、聚合物浓度等因素对微孔形态与薄膜性能的影响.研究表明,聚苯硫醚-己内酰胺体系以固液分相为主,萃取后形成球晶状的微孔结构.降温速率对薄膜的微孔形态、孔径以及连通性有重要影响;当体系以较低降温速率冷却时,多孔形态为枝叶状,形成了更多的开孔结构并获得了更大的孔径,这是获得高通量微孔膜的主要原因.通过控制降温速率可以制备纯水通量大于100 L/m2h,孔径约4～5μm且连通性良好的聚苯硫醚微孔膜;研究了聚合物浓度的影响,薄膜的纯水通量随着聚合物浓度的增大而减小,并且当聚苯硫醚浓度>50 wt%时,由于大于临界浓度而失去渗透性.     

聚乙二醇对聚醚砜微孔膜致孔作用的研究

以聚醚砜聚乙二醇溶剂为铸膜液体系、采用干湿相转化法制备微孔滤膜,研究了各种制膜条件对膜孔径结构的影响.实验发现聚乙二醇在体系中起到分散稳定的作用,只有到浓度大于70%时,才会对铸膜液的粘度产生明显影响,聚合物在铸膜液中的溶解状态也随之改变,进而影响膜的结构.不同溶剂NMP、DMF、DMAc、DMSO等极性溶剂或固体溶剂己内酰胺均可制得开孔率较高的微孔膜,但对膜的结构和性能影响差别不大.在本研究体系中,膜的结构取决于聚乙二醇、溶剂的浓度比例关系.     

热致相分离法制聚偏氟乙烯微孔膜稀释剂的选择

依据聚偏氟乙烯(PVDF)、邻苯二甲酸二甲酯、水杨酸甲酯、卡必醇醋酸酯、三醋酸甘油酯、邻苯二甲酸二正丁酯(DBP)、苯乙酮和二苯甲酮(DPK)的Hansen溶度参数及其相对介电常数, 选择能与PVDF以液-液相分离机理进行热致分相的稀释剂, 制备了具有双连续结构的微孔膜. 通过比较PVDF-稀释剂间的溶度参数及相对介电常数的差异, 发现PVDF-DBP体系和PVDF-DPK体系有发生热致液-液相分离的可能. 实时观察上述两个体系的分相过程并测定其结晶温度, 当PVDF质量分数低于30%时, 随着温度的降低, PVDF-DPK体系发生液-液相分离. 根据PVDF-DPK体系相图, 通过控制PVDF含量和降温条件, 无须添加非溶剂或拉伸工艺, 就可以制备出具有双连续结构的PVDF微孔膜.     

溶剂对相分离法制备聚偏氟乙烯微孔膜性质的影响

研究了用相转换法制备聚偏氟乙烯（PVDF）微孔膜时溶剂对成膜性质的影响.用浊点法测定了二甲基亚砜、N,N-二甲基甲酰胺、N,N-二甲基乙酰胺、N-甲基吡咯烷酮、磷酸三甲酯等五种溶剂配制的质量分数为wPVDF=0.12的铸膜液在30℃时的相分离点,显微镜拍照法测定了这些铸膜液与水接触时相分离前沿推进速率,泡点法测定了膜孔径,并测定了气体通量.结果表明,二甲基亚砜、磷酸三甲酯、N,N-二甲基乙酰胺是适于制作聚偏氟乙烯微孔膜的溶剂.     

工艺条件对 LLDPE/POE/CaCO3微孔膜的孔结构及防水透湿性能的影响

用拉伸致孔法制备了 LLDPE/POE/CaCO3防水透湿微孔膜,研究了拉伸倍数及体系组成对微孔膜的微孔结构及防水透湿性能的影响.用 SEM 对微孔膜的微孔结构进行考察,用压汞法对微孔膜的孔径及其分布和微孔的孔隙率进行研究.用静水压法及正杯法分别研究了微孔膜的防水和透湿性能.结果表明:拉伸倍数及 CaCO3用量对微孔膜的孔径、孔隙率及防水透湿性能有明显影响.     

热致相分离法制备聚烯烃微孔膜研究进展

非极性及弱极性的结晶高聚物常温下无合适的良溶剂,所以无法使用传统的非溶剂致相分离法制取微孔膜,而近年来发展的热致相分离法解决了这一问题。研究发现聚乙烯、聚丙烯、乙烯．乙烯醇共聚物、乙烯．丙烯酸共聚物、聚(4-甲基-1-戊烯)等聚烯烃是可采用热致相分离法制备微孔膜的材料。本文综述了近年来在热致相分离法制备聚烯烃微孔膜方面的研究进展,重点介绍各种制膜材料(聚合物、稀释剂、萃取剂和助剂)与各种制膜工艺对制得的聚烯烃微孔膜孔径、膜通量和非对称结构等的影响。     

相转换法制备聚氨酯微孔膜过程中的非溶剂效应

利用湿法相转换的原理制备聚氨酯微孔薄膜,从实验和理论计算两方面研究了非溶剂组成对聚氨酯孔结构及相分离过程的影响.实验结果表明:与水体系相比,在醇类非溶剂体系中聚氨酯膜更易形成较均一形貌的多孔结构.用异丙醇作非溶剂可得到孔径均一、相互贯通的孔结构.而理论计算结果表明:这种非溶剂效应与水、甲醇、乙醇及异丙醇等非溶剂系统的Flory-Huggins 相互作用参数及扩散系数密切相关.     

TIPS法制备聚偏氟乙烯平板微孔膜及其表征

以邻苯二甲酸二甲酯(DMP)为稀释剂,采用热致相分离法(TIPS)制备了聚偏氟乙烯(PVDF)平板微孔膜。利用差示扫描量热仪分析了不同PVDF/DMP体系的结晶性能;通过测试纯水通量、孔隙率、泡点、平均孔径、拉伸强度等对膜进行了表征。结果表明:DMP含量增大,结晶温度向低温方向移动,膜拉伸强度降低,当DMP的质量分数为0.70时膜拉伸强度有明显拐点;PVDF/DMP体系冷却发生固-液相分离;PVDF含量增大,膜水通量、孔隙率、最大孔径和平均孔径均减小。     

Polysulfone Membranes via Thermally Induced Phase Separation

Polysulfone (PSF) membranes have gained great attention in the fields of ultrafiltration,microfiltration,and thin film composite membranes for nanofiltration or reverse osmosis.For the first time,it is proposed to fabricate PSF membranes via thermally induced phase separation (TIPS) process using diphenyl sulfone (DPSO2) and polyethylene glycol (PEG) as mixed diluent.DPSO2 is chosen as a crystallizable diluent,while PEG is considered in terms of molecular weight (Mw) and dosage.We systematically investigate the interactions between PSF,DPSO2 and PEG based on the simulation calculations and solubility parameter theory.It is inferred that DPSO2 has an excellent compatibility with PSF,and the addition of PEG results in the ternary system thermodynamically less stable and then facilitates its liquid-liquid (L-L) phase separation.SEM images indicate that cellular-like pores are obvious throughout the membrane when the PEG content in the mixed diluent is 25 wt％-35 wt％.We can facilely manipulate the pore size,water flux and mechanical properties of PSF membranes with the dosage of PEG-200,the Mw of PEG or the cooling rate.The successful application of TIPS can provide a new approach for structure manipulation and performance enhancement of PSF membranes.     

Effect of cooling baths on EVOH microporous membrane structures in thermally induced phase separation

The purpose of this work is to investigate the effect of cooling bath on the membrane preparation of crystalline polymer/diluent system via thermally induced phase separation (TIPS), when the cooling bath is compatible with the diluent. In this work, poly(ethylene-co-vinyl alcohol) (EVOH)/PEG300 system with water and methanol as the cooling baths was proposed. Results showed that when water was used as the cooling bath, the membrane presented an asymmetric structure consisting of a porous skin, macrovoids near the top and lacy structures near the bottom. In contrast, when cooled in the bath of methanol, it showed particulate morphology on the top surface and cellular pores near the bottom. The lacy and cellular structures were the typical structures resulted from liquid–liquid thermally induced phase separation, the novel macrovoids and particulate morphology were then supposed to be induced by the mutual diffusion between the diluent and the cooling bath. In the case of water, the diluent's outflow was comparative with the water's inflow into the membrane, so the penetrated water acted as a strong nonsolvent and induced macrovoids near the top. In the bath of methanol, the diluent's outflow was much faster than the methanol's inflow, which changed the solution composition from a liquid–liquid phase separation region to a solid–liquid phase separation region and resulted in particulate morphology near the top.     

Polysulfone membranes <Emphasis Type="Italic">via</Emphasis> thermally induced phase separation

Polysulfone (PSF) membranes have gained great attention in the fields of ultrafiltration, microfiltration, and thin film composite membranes for nanofiltration or reverse osmosis. For the first time, it is proposed to fabricate PSF membranes via thermally induced phase separation (TIPS) process using diphenyl sulfone (DPSO2) and polyethylene glycol (PEG) as mixed diluent. DPSO2 is chosen as a crystallizable diluent, while PEG is considered in terms of molecular weight (M _w) and dosage. We systematically investigate the interactions between PSF, DPSO2 and PEG based on the simulation calculations and solubility parameter theory. It is inferred that DPSO2 has an excellent compatibility with PSF, and the addition of PEG results in the ternary system thermodynamically less stable and then facilitates its liquid-liquid (L-L) phase separation. SEM images indicate that cellular-like pores are obvious throughout the membrane when the PEG content in the mixed diluent is 25 wt%?35 wt%. We can facilely manipulate the pore size, water flux and mechanical properties of PSF membranes with the dosage of PEG-200, the M _w of PEG or the cooling rate. The successful application of TIPS can provide a new approach for structure manipulation and performance enhancement of PSF membranes.     

EFFECT OF DILUENTS ON CRYSTALLIZATION OF POLY(VINYLIDENE FLUORIDE) AND PHASE SEPARATED STRUCTURE IN A TERNARY SYSTEM via THERMALLY INDUCED PHASE SEPARATION

The phase diagram of a ternary system of PVDF,dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) was determined in terms of a pseudo binary system with the same polymer concentration and different DBP content in diluent mixture.The experimental results showed that as the DBP content increased in diluent mixture,the phase separation changed from liquid-liquid phase separation to solid-liquid phase separation,and both the cloudy point for L-L phase separation and crystallization temperature shif...     

A novel method for the pore size control of the battery separator using the phase instability of the ternary mixtures

The battery separator plays a key role in determining the capacity of the battery. Since separator performance mainly depends on the pore size of membrane, development of a technique for the fabrication of the membrane having controlled pore size is essential in producing a highly functional battery separator. In this study, microporous membranes having the desired pore size were produced via thermally‐induced phase separation (TIPS) process. Control of the phase boundaries of polymer‐diluent blends is the main concern in manipulating pore size in TIPS process, because pore size mainly depends on the temperature gap between phase separation temperature of the blend and the crystallization temperature of polymer. Microporous membranes having controlled pore size were produced from polyethylene (PE)/dioctyl phthalate (DOP) blends, PE/isoparaffin blends, and polymer/diluent‐mixture ternary blends, that is, PE/(DOP/isoparaffin) blends. PE/DOP binary blends and PE/(DOP/isoparaffin) ternary blends exhibited typical upper critical solution temperature (UCST) type phase behavior, while PE formed a homogeneous mixture with isoparaffin above the crystallization temperature of PE. When the mixing ratio of polymer and diluent‐mixture was fixed, the phase separation temperature of PE/diluent‐mixture blend first increased with increasing DOP content in the diluent‐mixture, went through a maximum centered at about 80 wt % DOP and then decreased. Furthermore, the phase separation temperatures of the PE/diluent‐mixture blends were always higher than that of the PE/DOP blend when diluent‐mixture contained more than or equal to 20 wt % of DOP. Average pore size of microporous membrane prepared from PE/DOP blend and that prepared from PE/isoparaffin blend were 0.17 and 0.07 μm, respectively. However, average pore size of microporous membrane prepared from ternary blends was varied from 0.07 to 0.5 μm by controlling diluent mixing ratio. To understand the phase behavior of ternary blend, phase instability of the ternary mixture was also explored. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2025–2034, 2006     

Phase behavior of polymer/diluent/diluent mixtures and their application to control microporous membrane structure

Rechargeable battery separators containing controlled pores were fabricated via the thermally-induced phase separation (TIPS) process. Based on the idea that pores could be manipulated by controlling the liquid–liquid phase separation temperature in the TIPS process, phase boundaries of the polymer–diluent systems were controlled by using diluent mixtures. Phase behaviors of the polymer/diluent/diluent ternary blends consisting of polyethylene (PE) as polymer, and soybean oil (SBO) and dioctyl phthalate (DOP) as diluents were explored. PE/SBO and PE/DOP binary blends, and PE/SOB/DOP ternary blends exhibited typical upper critical solution temperature (UCST) type phase behaviors, and the phase separation temperatures of the PE/SBO blends were higher than those of the PE/DOP blends. When the mixing ratio of the polymer and diluent-mixture was fixed, the phase separation temperature of the PE/SBO/DOP blend initially increased with increasing SBO content in the diluent-mixture passing through a maximum centered at about 80 wt% SBO and decreased beyond this point. Furthermore, the phase separation temperature of the PE/diluent-mixture blend was always higher than that of the PE/SBO blend when the diluent-mixture contained more than or equal to 50 wt% SBO. To understand the observed phase behavior of the blends, thermodynamic analyses based on the lattice-fluid theory were performed. Larger pore membranes were fabricated from the blend when higher phase separation temperatures of the blend were exhibited.     

热致相分离法偏二氯乙烯-氯乙烯共聚物多孔膜的制备及性能

以偏二氯乙烯-氯乙烯共聚物[P(VDC-co-VC)]为成膜聚合物, 邻苯二甲酸二甲酯(DMP)为稀释剂, 采用热致相分离(TIPS)法制备了具有多孔结构的P(VDC-co-VC)膜. 通过聚合物-稀释剂二元体系相图、 场发射扫描电镜(FESEM)、 差示扫描量热仪(DSC)、 X射线衍射(XRD)、 原子力显微镜(AFM)、 纯水通量、 接触角、 孔径及其分布、 截留率及力学性能等研究了聚合物含量对P(VDC-co-VC)多孔膜结构和性能的影响. 结果表明, P(VDC-co-VC)-DMP二元体系成膜过程以液-液(L-L)分相为主, 随着聚合物含量增加, 膜的横截面由类花瓣状结构向胞腔状结构转变, 膜的孔连通性降低, 结构变得较为致密, 同时膜上表面孔隙率降低, 粗糙度增大. L-L分相时间和聚合物含量的变化, 导致膜结晶度先降低后增大. 聚合物含量的增加使膜上表面接触角、 断裂强度及蛋白截留率增加, 但膜的平均孔径、 孔隙率及纯水通量先增加后减小. 当聚合物质量分数为30%时, 所得膜通透性较优, 断裂强度可达7.5 MPa.     

PREPARATION OF MICROPOROUS ULTRA HIGH MOLECULAR WEIGHT POLYETHYLENE (UHMWPE) BY THERMALLY INDUCED PHASE SEPARATION OF A UHMWPE/LIQUID PARAFFIN MIXTURE

Ultra-high molecular weight polyethylene (UHMWPE) with a microporous structure was prepared via thermally induced phase separation (TIPS).Liquid paraffin (LP) was used as a diluent in the preparation of microporous UHMWPE. Small angle laser light scattering (SALLS) and differential scanning calorimetry (DSC) were used to determine the phase separation temperatures,i.e.the cloud points and the dynamic crystallization temperatures,respectively.It was found that the cloudI points were coincident with the cr...