南京工业大学
硕士学位论文
热致相分离法制备聚偏氟乙烯微孔膜
海外教育考试中心姓名：顾明浩
申请学位级别：硕士
专业：材料学
指导教师：张军debris
may day20060531
硕士学位论文
摘要
聚偏氟乙烯（PVDF）是一种白色粉末状结晶聚合物，其化学稳定性良好，室温下不受酸、碱等强氧化
剂和卤素腐蚀。由于其上述优点，美国Millipore公司于20世纪80年代中期首先使用该高聚物开发出“Durepore”型的微孔滤膜。PVDF微滤膜以其疏水性已成功地应用于油水分离、废水处理、工业气体过滤等场合。制备PVDF微孔膜有浸没沉淀法和热致相分离法。热致相分离法拓宽了膜材料的范围，开辟了相分离法制备微孔膜的新途径。
本论文选用单用和混合稀释剂，以TIPS法制备PVDF微孔膜。研究稀释剂对PVDF微孔膜结构的影响，PVDF/邻苯二甲酸二甲酯（DMP）体系中PVDF 结晶动力学对PVDF微孔膜结构的影响，PVDF/二苯甲酮体系中相分离机理对PVDF微孔膜结构的影响，并研究添加剂聚四氟乙烯（PTFE）和高岭土（Clay）以及拉伸工艺对PVDF微孔膜结构的影响。
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选择与PVDF相互作用较强的邻苯二甲酸二甲酯，邻苯二甲酸二丁酯（DBP），水杨酸甲酯（MS）和二苯甲酮（benzophenone）为PVDF的单用稀释剂，同时选择与PVDF相互作用较小的癸二酸二辛酯（DOS）、己二酸二辛酯(DOA)和邻苯二甲酸二乙基己酯（DOP）、对苯二甲酸二异辛酯（DOTP）与DMP、DBP 以一定的比例形成混合稀释剂。由于稀释剂与聚合物的相互作用的不同得到不同的微孔膜结构。PVDF/DMP、PVDF/DMP/DOA、 PVDF/DBP和PVDF/DMP/DOS 四种聚合物/稀释剂体系微孔膜的孔隙率受稀释剂与聚合物相互作用影响。对于PVDF/DMP/DOA三元体系，体系偏晶点低于PVDF/DMP二元体系，浊点和结晶曲线相对于PVDF/DMP体系也偏移到较高的温度，这说明DMP/DOP与PVDF 的相容性低于DMP，同时偏晶点偏移到高聚合物浓度，导致聚合物/稀释剂体系在
降温过程中液滴生长的时间较长。在不同聚合物浓度下，微孔膜呈现不同的结构和形态，这与体系的粘度有关。同时微孔膜的结构和形态受不同的淬冷和粗化作用的影响，这直接通过相分离机理来控制。
选取三个温度：95℃（L-L相分离区域）；85℃（PVDF初始结晶峰值温度）；80℃（PVDF初始结晶峰值温度以下），研究PVDF/DMP体系的富聚合物相的相分离结晶行为。在PVDF/DMP体系中，在相分离的初始阶段，体系的结晶度随着时间的增加而增加，在相分离的后期，结晶度增加到恒定值。在三种淬冷温度
摘要
下，体系结晶速率大小为：V80℃>V85℃>V95℃，这与相分离的机理有关。.在室温空气浴下由于结晶速率较低，PVDF结晶较完善。冰水混合物淬冷条件下，淬冷度最大，结晶速度最快，晶核形成最多。30℃水浴下淬冷，淬冷度相对冰水混合物小，结晶不完善，球晶尺寸大小不一。根据宽角X射线衍射分析的结果，当淬冷温度在40℃至110℃，发现PVDF/DMP体系中PVDF的晶型为α晶型，在不同的淬冷温度下，衍射峰随淬冷温度而变化。PVDF/DMP二元体系在液氮淬冷后在25℃水浴结晶24h，PVDF/DMP体系中存在β晶型的PVDF。
acrossfrom以二苯甲酮为稀释剂，在PVDF微孔膜的制备过程中，发现固-液相分离和固-固相分离对微孔膜的结构英语绕口令
和形态有很大影响。在不同的淬冷温度下，由于固-液相分离过程中伴随固-固相分离，得到不明显球晶结构的微孔膜结构，而含有明显球晶结构的微孔膜结构出现在固-液相分离过程中，并且通过宽角X射线衍射的分析证明上述机理的存在。同时PVDF微孔膜的结构受聚合物初始浓度的影响，随着PVDF初始浓度的增加，富聚合物相尺寸有减小的趋势。在DSC过程中，发现熔融双峰现象，这与在不同的热处理过程中PVDF结晶程度不同有关。0℃淬冷条件下熔融峰值温度介于80℃淬冷的第一和第二熔融峰值温度之间，且PVDF的结晶度在此温度下比80℃低5%，所以在80℃淬冷条件下得到含明显球晶的微孔膜结构形成，而0℃淬冷球晶结构不明显。
毛孔怎么变小
选择低毒性的水杨酸甲酯（MS）为PVDF的稀释剂，随着PVDF初始浓度的增加，PVDF/MS体系在高温下形成溶液的粘度增加，在淬冷过程中PVDF的流动性随着粘度的增加而降低，PVDF结晶速度减慢，从而球晶尺寸减小。添加剂PTFE的加入减小PVDF球晶的尺寸，降低体系中PVDF的结晶度，而添加剂高岭土的加入促进PVDF的结晶，提高PVDF的结晶度。同时拉伸使晶区和非晶区内分子链排列有序化转变，提高体系的结晶度。在未加添加剂以及加入1%PTFE的体系拉伸前后中只存在α晶型的PVDF，在加入1%高岭土拉伸前后体系同时存在α晶型和β晶型的PVDF。由于在室温下拉伸温度较低，聚合物的分子链或者球晶中的结构单元没有足够的活动性，因此只能观察到球晶在拉伸下或者脆裂或者沿边界分裂，而观察不到较大的形变。拉伸对最终微孔膜的形态和孔隙率产生影响，微孔膜出现明显取向的球晶和不规则的微孔。
关键词：聚偏氟乙烯微孔膜热致相分离稀释剂膜结构
硕士学位论文
ABSTRACT
Poly(vinylidene) fluoride(PVDF) is the typical mi-crystal polymer with its good properties of chemical and aging resistance for membrane formation. The Millipore Company firstly develops “Durepore” microporous membrane with PVDF as membrane material in the middle of 1980s. At prent, the PVDF membrane is successfully ud in the oil-water paration, waste water disposal and gas filtration. There are veral methods for PVDF membrane preparation, such as immer precipitation, and thermally induced pha paration(TIPS). The TIPS broadens the membrane preparation materials, and easily makes the crystal polymer suitable for membrane materials.
The effect of single and mixing diluents, the crystallization behavior of PVDF in PVDF/Dimethylphthalate(DMP) system, the different pha paration mechanisms in PVDF/benzophenone system, the additives polytetrafluoroethylene(PTFE) and clay, drawing technique on the membrane structure were studied.maven
The four diluetns DMP, dibutyl phthalate(DBP), methyl salicylate(MS) and benzophenone with strong interactions with PVDF were chon as the single diluent. The dioctyl bacate(DOS), dioctyl adipate(DOA), dioctyl phthalate(DOP), and dioctyl terephthalate(DOTP) with weak interactions with PVDF were chon as the mixing diluents. The different interactions between diluents and polymer resulted in the different membrane structure. As the interactions decread, the spherulitic structure was more non-discernable and the porosity incread in the order of PVDF-DMP, PVDF-DMP-DOA, PVDF-DBP and PVDF-DMP-DOS. This order can be explained by the compatibility between PVDF and diluents.
The crystallization rate and crystallinity were in the order of 80℃, 85℃ and 95℃ in the early stage of pha paration. Crystallinity of PVDF in PVDF-DMP system incread in the early stage of pha paration, and PVDF crystallized completely in the late stage of pha paration. In different quenching conditions, the greatest size and the mature of spherulites were obtained in air bath, the great amount of spherulites were obtained in ice water, and the irregular size of spherulites were
ABSTRACT
formed in 30℃ water bath. In particular, when PVDF-DMP system quenching to different temperatur
es above 40℃, α-pha PVDF was obtained in PVDF-DMP system, and as quenching temperatures changed, the area of diffraction peak changed. The β-form PVDF was obtained when PVDF-DMP system was quenching from liquid nitrogen and crystallized 24 hours in 25℃ water bath.
The benzophenone was chon as the diluent for PVDF. The two pha paration mechanisms: solid-solid(S-S) and solid-liquid(S-L) pha paration determined the final membrane structure. In the different quenching temperatures, the non-discernable spherulitic membrane structure is formed via S-L pha paration accompanying with S-S pha paration, and the discernable membrane structure was formed only via S-L pha paration, which was proved by the WAXD. The dual melting peak behavior was discovered in the DSC process. The high crystallinity of PVDF was obtained when quenched at 80℃ for 20min, and the discernable spherultic membrane structure is formed, while the non-discernable spherultic membrane structure was formed when quenched at 0℃ for 20min.
The viscosity of PVDF/MS solution incread as the PVDF weight concentration incread. So the crystallization rate of PVDF decread, and the spherulite size decread. The added PTFE reduced the spherulite size and crystallinity of PVDF, while the additive clay incread the crystallinity of PVDF. The arrangement of macromolecular chain in the crystal and amorphous region
was enhanced as the effect of drawing, and the crystallinity in the PVDF/MS system incread. The α-form PVDF was obtained in the PVDF/MS system without the additives and the PVDF/MS system added with 1% PTFE before and after drawing, while the α-form and β-form PVDF were obtained in the PVDF/MS system added with 1% clay before and after drawing. The drawing had the effect on the final membrane structure and porosity, the obvious directional spherulites were formed with irregular pores.
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KEYWORDS: PVDF；Microporous membrane；Thermally induced pha paration；Diluents；Membrane structure
