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.     

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。     

热致相分离法高效制备压电聚偏氟乙烯膜

以环保溶剂乙酰柠檬酸三丁酯(ATBC)为稀释剂，绿色无毒的离子液体1-丁基-3-甲基咪唑六氟磷酸盐([BMIM][PF₆])为添加剂，采用热致相分离(TIPS)法制备聚偏氟乙烯(PVDF)微滤膜，通过扫描电子显微镜观察不同添加剂含量PVDF膜的微观形貌；通过超滤杯对PVDF膜的纯水通量进行了测试；使用拉力计对PVDF膜的机械性能进行了表征；通过红外光谱和X-射线衍射研究了添加剂对PVDF膜晶型结构的影响。结果表明：加入1.0%[BMIM][PF₆]时，PVDF的晶型变为β- 晶型。     

聚偏氟乙烯基含氟聚合物介电和储能研究进展

聚偏氟乙烯（PVDF）和偏氟乙烯（VDF）／三氟乙烯（TrFE）二元共聚物以其优异的铁电、压电性能而备受关注。近年来,该类聚合物经物理／化学改性后表现出非常优异的介电、储能性能,尤其在高储能放电电容器领域被寄予厚望。经分子组成优化和挤出拉伸处理的PVDF基含氟聚合物在室温下具有高介电常数（12～60）,高击穿电场强度,...     

高温热处理对偏氟乙烯-四氟乙烯共聚物高次结构的影响

聚偏氟乙烯(PVDF)及其一些共聚物,例如偏氟乙烯-四氟乙烯共聚物(PVDF/TFE)经过处理后呈现较强的压电性。许多研究表明它们是铁电聚合物,而且压电活性与样品的高次结构有关。松弛谱是研究结晶高聚物的高次结构的有力工具,近来,Koizumi等人报道了PVDF/TFE的热处理与松弛现象的关系。本文作者也报道了     

相分离对聚偏氟乙烯/聚甲基丙烯酸甲酯共混物的力学与耐紫外老化性能的影响

采用熔融共混法制备聚偏氟乙烯/聚甲基丙烯酸甲酯( PVDF/PMMA)共混物,考察其力学性能、耐紫外老化性能、熔体动态流变、结晶与热分解行为.PMMA含量(wPMMA)为10 wt％时,共混物形成均相结构,力学与耐老化性能最好.wPMMA≥20 wt％时,PMMA形成球状聚集体,共混物力学性能与耐候性显著降低.PMMA的存在可提高PVDF的结晶度,降低熔融温度,但不改变PVDF晶体结构.     

碳纳米管的加入对聚偏氟乙烯/丙烯酸酯共混物形状记忆性能的影响

利用聚偏氟乙烯(PVDF)微小结晶的物理交联点作用,制备了形状记忆性能优异的聚偏氟乙烯/丙烯酸酯聚合物(PVDF/ACM)共混材料。为提高其形状回复应力,又将碳纳米管(CNT)引入该共混体系中,系统研究了PVDF/ACM/CNT三元体系纳米复合材料的制备、结构及性能。结果表明,碳纳米管在PVDF/ACM体系中分散均匀;在基本保持其形状记忆性能的前提下,加入质量分数为4%的CNT,材料在25℃时的储能模量由2000 MPa提高至3130 MPa。     

聚偏氟乙烯/蒙脱土纳米复合材料的形态结构

采用有机改性的蒙脱土与聚偏氟乙烯熔融共混, 制备了聚偏氟乙烯/蒙脱土纳米复合材料. 利用X射线衍射分析、透射电子显微镜(TEM)和Molau实验研究了复合材料的微观结构. 通过X射线衍射、傅里叶变换红外光谱(FTIR)以及差热扫描(DSC)研究了有机改性蒙脱土对聚偏氟乙烯结晶结构的影响. 结果表明, 有机改性蒙脱土在聚偏氟乙烯中以插层、剥离和碎片的形式存在. 在X射线衍射谱中发现蒙脱土的(001)峰向低角方向移动, 在TEM中可见到剥离的片层碎 片.蒙脱土的引入改变了聚偏氟乙烯的结晶结构, 导致了具有压电性能的β相形成, 引起α相内应力的产生, 同时也导致了聚偏氟乙烯基体的结晶度下降, 球晶尺寸随蒙脱土含量明显减少. 蒙脱土引起的β相在 160℃退火表明是相当稳定的. 根据这些实验结果, 对由于蒙脱土的引入引起的聚偏氟乙烯结晶结构的变化提出了可能的解释.     

增强复合静电纺纳米纤维膜

静电纺丝纳米纤维膜具有孔隙率高、孔径小、透气性好等优良性能。但由于纤维太细,且纤维间没有有效的粘结,其强度较低,严重限制了它的应用。本文采用高/低熔点热熔性的两种高聚物进行混合静电纺丝,制备了聚丙烯腈/聚偏氟乙烯-六氟丙烯(PAN/PVDF-HFP)、聚偏氟乙烯/聚偏氟乙烯-六氟丙烯(PVDF/PVDF-HFP)复合纳米纤维膜,并通过110℃、3MPa、5min的热压后处理,使PVDF-HFP部分熔融,制得具有点粘结的增强复合纳米纤维膜。测试结果显示,较处理前,增强PAN/PVDF-HFP、PVDF/PVDF-HFP复合纳米纤维膜的拉伸断裂强度分别提高了923.1%和665.7%,达到17.8MPa和26.9MPa,且同时保留了优良的孔隙率与透气性能。     

四甲基氢氧化铵改性聚偏氟乙烯接枝苯乙烯磺化膜的制备和性能

使用四甲基氢氧化铵(TMAH)甲醇溶液在液相中改性聚偏氟乙烯(PVDF),挥发溶剂得到改性聚偏氟乙烯膜(g-PVDF-M),再以过氧化苯甲酰(BPO)为引发剂,将苯乙烯接枝到g-PVDF-M膜中,磺化后制得改性聚偏氟乙烯接枝苯乙烯磺化(PVDF-g-PSSA)膜.利用傅里叶变换红外光谱(FTIR)和能谱仪的扫描电子显微镜分析了PVDF-g-PSSA膜(TMAH-25)的结构、形貌及硫元素分布情况.通过电化学工作站和气相色谱仪研究了TMAH在甲醇中的不同含量对PVDF-g-PSSA膜质子电导率和甲醇渗透率的影响.结果表明,TMAH使PVDF脱去HF生成碳碳双键,并且苯乙烯接枝到改性的聚偏氟乙烯膜中,磺化后S元素在PVDF-g-PSSA膜内部均匀分布;PVDF-g-PSSA膜的质子电导率和甲醇渗透率随TMAH在甲醇溶液中质量分数的增加而增大;TMAH的质量分数为25%时,PVDF-g-PSSA膜的电导率达1.28×10~(-2)S/cm,甲醇渗透率为4.58×10~(-7)cm~2/s.热重分析(TGA)表明,PVDF-g-PSSA膜的热稳性良好,耐热温度高达195℃,PVDF-g-PSSA膜作为电解质材料的直接甲醇燃料单电池(DMFC)功率密度达到16.45 mW/cm~2.     

Morphologies and crystalline forms of polyvinylidene fluoride membranes prepared in different diluents by thermally induced phase separation

We have studied the morphologies and crystalline forms of polyvinylidene fluoride (PVDF) membranes separately prepared in four different diluents bearing >C?O groups, namely 1,2‐propylene glycol carbonate (PGC), dimethyl phthalate (DMP), diphenyl ketone (DPK), and dibutyl phthalate (DBP), by the thermally induced phase separation (TIPS) method. The permittivities of the diluents and PVDF were measured to compare the different PVDF–diluent systems. The results showed the permittivity of PGC to be much greater than that of PVDF, and those of DMP and DBP to be lower than that of PVDF. The permittivity difference between DPK and PVDF was not apparent above 120 °C. On cooling mixtures with a PVDF concentration of 10 wt %, PVDF crystallization was observed in the PVDF–DMP, PVDF–DBP, and PVDF–PGC systems, while liquid–liquid phase separation occurred in the PVDF–DPK system. A cross‐section of the PVDF–PGC membrane presented smooth PVDF particles in the β‐phase crystalline form. Those of the PVDF–DMP and PVDF–DBP membranes presented PVDF particles consisting of a fibrillar network in the α‐phase. The PVDF–DPK membrane preferentially adopted an α‐phase bicontinuous channel structure. When the concentration of PVDF was 60 wt %, the cross‐sections of the above four membranes revealed PVDF polyhedra, among which the PVDF–DMP, PVDF–DBP, and PVDF–DPK membranes retained the α‐phase crystalline form, and the diffraction peak of the α‐phase became visible in the X‐ray diffraction (XRD) spectrum of the PVDF–PGC membrane. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

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...     

Thermally induced phase separation of poly(vinylidene fluoride)/diluent systems: Optical microscope and infrared spectroscopy studies

Thermally induced phase separation (TIPS) has been developed to prepare porous membranes. The porous structures are mainly dependent on diluents adopted in the TIPS process. We obtained two typical morphologies of poly(vinylidene fluoride) (PVDF) membranes using cyclohexanone (CO) and propylene carbonate (PC) as diluents, respectively. SEM observation displays that porous spherulites are formed from PVDF/CO system, whereas smooth particles result from PVDF/PC system. The TIPS processes of these two systems have been investigated in detail by optical microscope observation and temperature‐dependent FTIR combined with two‐dimensional infrared correlation analysis. Rapid crystallization of PVDF can be seen around 110 °C in the PVDF/CO system, which is consistent with the results of temperature‐dependent FTIR spectra. The spectral evolution indicates a transform of PVDF from amorphous to α‐phase after 110 °C. The ν_s(C?O) band at 1712 cm^?1 narrows and the ν_s(C? F) band at 1188 cm^?1 shifts to 1192 cm^?1 before crystallization, which implies the destruction of interaction between PVDF and CO. In contrast, the PVDF/PC system shows slow crystallization with all‐trans conformation assigned to β‐phase and γ‐phase below 60 °C but no obvious change of polymer?diluent interaction. We propose two mechanisms for the different phase behaviors of PVDF/CO and PVDF/PC systems: a solid?liquid phase separation after destruction of polymer?diluent interaction in the former, and a liquid?liquid phase separation process coupled with rich‐phase crystallization in the later. This work may provide new insight into the relationship among morphologies, crystal forms, and phase separation processes, which will be helpful to adjust membrane structure. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1438–1447     

P[MMA-IL]修饰石墨烯协同调控PVDF复合物结晶与介电行为

为改善石墨烯(Gra)在聚偏氟乙烯(PVDF)中的分散性和界面性质,以甲基丙烯酸甲酯(MMA)和1-乙烯基-3-乙基咪唑溴盐(IL)为单体合成P[MMA-IL]共聚物,用于修饰石墨烯(Gra),并通过溶液共混、热压法制备PVDF/PMMA、PVDF/P[MMA-IL]、PVDF/PMMA/Gra和PVDF/P[MMA-IL]/Gra复合薄膜.采用Raman光谱、场发射扫描电子显微镜(FESEM)、傅里叶变换反射红外光谱分析仪(FTIR-ATR)、X射线衍射仪(XRD)、偏光显微镜(POM)、示差扫描量热仪(DSC)和电感电容电阻测试仪(LCR)对复合薄膜的结构形态、结晶与介电行为进行表征和分析.Raman光谱表明P[MMA-IL]与Gra之间存在强相互作用;FESEM照片显示P[MMAIL]能够促进Gra在基体中的分散;DSC、XRD和FTIR-ATR数据表明PMMA降低PVDF的结晶温度,PMMA和Gra未能诱导出?-PVDF极性晶体,而单独的P[MMA-IL]会通过咪唑阳离子-偶极子作用诱导?-PVDF晶体;通过咪唑阳离子-π强相互作用,P[MMA-IL]在模板剂Gra表面进行修饰,协同诱导作用增强.POM照片表明?-PVDF晶体在生长过程中,MMA链段会嵌入到球晶的晶片空隙中,引起结构疏松;离子-偶极子和IL成核作用导致?-PVDF晶体尺寸较小,结晶较快.介电行为研究表明PMMA及其修饰Gra降低PVDF的结晶度和链浓度,导致界面极化和取向极化较弱,介电响应较弱;而P[MMA-IL]修饰Gra诱导的?-PVDF晶体、以及IL链段在界面的离子极化使得界面极化作用增强,介电响应增强.     

Positive Temperature Coefficient Characteristics of Multi-walled Carbon Nanotube Filled Polyvinylidene Fluoride Nanocomposites

Composites of polyvinylidene fluoride (PVDF) and multi-wall carbon nanotubes (MWNT) were prepared by a melt mixing process. Temperature dependence of electrical properties of the nanocomposites was investigated for composites containing different amounts of MWNT. An obvious positive temperature coefficient was observed. It was found that resistivity of the composites was decreased with increasing MWNT content and the electrical percolation threshold was formed at 3 wt% MWNT, which were caused by the formation of conductive chains in the composites. The mechanism of the positive temperature coefficient behavior of the nanocomposites is discussed. The rheological results showed that the materials experience a fluid–solid transition at the composition of 2 wt%, beyond which a continuous MWNT network forms throughout the matrix leading to a percolated network structure, which further indictes the nanotubes were dispersed uniformaly, in the PVDF matrix.     

Extraction of sodium and potassium picrates with 16-crown-5 into various diluents. Elucidation of fundamental equilibria determining the extraction selectivity for Na(+) over K(+)

The constants of the overall extraction equilibrium (K(ex)), the partition for various diluents having low dielectric constants (K(D,MLA)), the aqueous ion-pair formation (K(MLA)), and the dimer formation in CCl(4) of 16-crown-5 (16C5)-alkali metal (Na, K) picrate 1:1:1 complexes were determined at 25 degrees C; the distribution constants of 16C5 were also measured at 25 degrees C. The logK(MLA) of Na and K are 4.14+/-0.19 and 3.05+/-0.28, respectively. The partition behavior of 16C5 and its 1:1:1 complexes with the alkalimetal picrates can be explained by regular solution theory, except for CHCl(3); the molar volumes and solubility parameters of 16C5 and the 1:1:1 complexes were determined. The magnitude of K(ex) largely depends on that of K(MLA). For every diluent, 16C5 always shows Na(+) extraction-selectivity over K(+). The K(MLA) value most contributes to the extraction selectivity of 16C5 for Na(+) over for K(+) among the three fundamental equilibrium constants, the aqueous 1:1 complex-formation constant of 16C5 with the alkali metal ion, K(MLA), and K(D,MLA). Furthermore, correct contributions of a methylene group to distribution constants of organic compounds between diluents of low dielectric constants and water were determined by the distribution constants of 16C5 and 15-crown-5; the additivity of the contributions of functional groups to the partition constant of a crown ether was verified.     

聚偏氟乙烯涂料的研究

用聚偏氟乙烯(PVDF)树脂制备了溶剂型氟碳涂料,筛选并优化了PVDF涂料的溶剂组成。采用丙烯酸树脂对PVDF进行改性,并研究颜填料钛白粉对涂膜性能的影响。结果表明,由甲苯、甲基异丁基酮、乙二醇乙醚乙酸酯、2,2,4-三甲基-1,3-戊二醇单异丁酸酯及邻苯二甲酸二甲酯组成的溶剂体系的涂料综合性能比较好,而丙烯酸树脂和钛白粉的加入明显地改善了PVDF涂膜的性能。     

聚偏氟乙烯薄膜压电性的研究

本文研究了聚偏氟乙烯的压电性。聚偏氟乙烯薄膜是用DMA溶剂浇铸而成,然后进行单轴拉伸,并采用热驻极的方法使薄膜成极。实验结果表明,压电活性依赖于拉伸比、极化电场、极化温度和极化时间。此外,还研究了聚偏氟乙烯压电薄膜的稳定性和某些使用特性。     

Intramolecular Crosslinking of Polyvinylidene Fluoride by Homogeneous Solution Irradiation

High Energy Chemistry - Intramolecular crosslinking of polyvinylidene fluoride (PVDF) was observed to have occurred when the PVDF homogeneous solution was subject to γ-ray irradiation, which...