PVDF复合材料的流变行为研究

采用RC90 HAAKE转矩流变仪对PVDF复合材料与PVDF进行流变性能研究,结果显示,PVDF复合材料与PVDF一样属于非牛顿流体,具有典型的切力变稀行为,PVDF复合材料的粘流活化能和非牛顿指数n较PVDF高,说明PVDF复合材料对剪切速率的依赖性较PVDF小。     

TiO_2溶胶改性PVDF超滤膜的制备与性能研究

利用溶胶-凝胶法制备二氧化钛(TiO2)溶胶并添加到铸膜液中,应用非溶剂致相法制备聚偏氟乙烯(PVDF)成品膜。系统研究了溶胶态TiO2、无机态Ti O2以及无机态TiO2/分散剂体系对TiO2/PVDF杂化膜的表面形貌、热稳定性、纯水接触角的影响。结果表明,溶胶态TiO2在铸膜液中分散良好,制取所得成品膜具有优良的综合性能,溶胶态TiO2的加入使得膜的接触角明显降低,孔隙率和平均孔径增大。     

PVDF/PMMA/TiO_2共混膜的结晶行为研究

采用流延法制备了聚偏氟乙烯(PVDF)/聚甲基丙烯酸甲酯(PMMA)/二氧化钛(TiO2)共混膜,利用红外光谱仪、X射线衍射仪、示差扫描量热仪研究了流延膜的结晶行为。结果表明,PVDF同时存在α、β两种晶型,PMMA、TiO2均能促使PVDF晶型从α晶向β晶转变。加入的PMMA增加了共混膜的非晶性,降低了PVDF的结晶度;TiO2亦能抑制PVDF结晶,降低体系的熔融温度。     

聚偏氟乙烯/聚醚酰亚胺共混溶液的流变性能研究

采用二甲基乙酰胺(DMAc)为溶剂配制不同共混比的聚偏氟乙烯(PVDF)和聚醚酰亚胺(PEI)共混溶液,用锥板式黏度计研究了PVDF/PEI共混溶液的流变性能。结果表明:PVDF/PEI共混溶液表观黏度与剪切速率呈线性相关;当PVDF/PEI质量比为9/1时,共混溶液的零切黏度明显降低,非牛顿指数和黏流活化能出现极值;随着PEI含量的增加,黏流活化能急剧增大。     

PVDF/TiO2复合膜的性能研究

采用流延成膜的加工工艺,制备了聚偏氟乙烯/二氧化钛(PVDF/TiO2)复合膜,研究了TiO2含量对复合膜的热稳定性、力学性能、结晶形态、热性能以及耐候性的影响。结果表明,TiO2含量为2%时,共混制得的复合膜拉伸强度高达59.5MPa,起始分解温度为340℃;加入TiO2对PVDF结晶度的影响不大,通过紫外照射实验证明加入TiO2改善了PVDF的耐候性。     

多功能PVDF/PVP/TiO_2复合材料的制备及性能研究

通过在聚偏二氟乙烯(PVDF)塑料薄膜上负载聚乙烯吡咯烷酮(PVP)改性TiO_2光催化纳米粒子制备了集油水分离和光催化降解功能为一体的多功能复合材料。由于改性TiO_2带来的粗糙结构,使得PVDF/PVP/TiO_2-2复合薄膜具有较高的油水分离性能,分离通量和拒油率分别为164 L/(m2·h)和99.8%。除此以外,PVDF/PVP/TiO_2-2复合薄膜在30 min内对甲基橙/甲苯乳液中甲基橙降解率达到了98.22%,并且对多种不同种类的可溶性污染物均具有较好的降解效果。循环稳定性方面,PVDF/PVP/TiO_2-2复合薄膜的分离性能以及光降解性能在经过10次循环后均为发生较大的下降,具有较好的实用性。     

二醋酸纤维素/离子液体溶液流变性能的研究

以离子液体1-丁基-3-甲基咪唑四氟硼酸盐([Bmim]BF4)为溶剂,制备了不同质量分数的二醋酸纤维素(CDA)/[Bmim]BF4溶液,采用旋转流变仪研究了溶液的稳态和动态流变行为,讨论了剪切速率、温度和CDA含量等因素对CDA/[Bmim]BF4溶液黏度的影响,并考察了Cox-Merz法则对CDA//[Bmim]BF4溶液体系的适用性。结果表明:CDA/[Bmim]BF4溶液为假塑性流体,表观黏度和零切黏度均随着质量分数的增加和温度的降低而增大;溶液的黏流活化能随着溶液质量分数增加增大;溶液不符合Cox-Merz法则;随着CDA/[Bmim]BF4溶液浓度增加,溶液中CDA大分子相互作用加剧,高浓度的CDA/[Bmim]BF4溶液需要更长的松弛时间。     

Surlyn/PMMA/PVDF共混物微观结构及性能的研究

采用聚甲基丙烯酸甲酯(PMMA)和乙烯-甲基丙烯酸共聚盐树脂(Surlyn)与聚偏二氟乙烯(PVDF)进行熔融共混,制备了Surlyn/PMMA/PVDF三元共混物。利用示差扫描量热法(DSC)、热重分析法(DTG)、X射线衍射(XRD)以及扫描电子显微镜(SEM)等测试方法分析共混物的微观结构和性能。结果表明,PMMA与PVDF有很好的相容性,且在一定程度上降低了共混物的结晶度与熔融温度,有利于PVDF进行塑化加工,同时导致PVDF的β相的形成。Surlyn的加入使得共混物分解温度比PVDF/PMMA提高,改善了共混物的热稳定性,提高了耐候性,但共混体系的结晶度并没有明显的改变。     

混合添加剂对TiO2/PVDF平板超滤膜性能和结构的影响

研究了不同比例的混合添加剂PEG600-LiCl、丙酮-LiCl、丙三醇-LiCl和PVP-LiCl对TiO2/PVDF平板超滤膜性能和结构的影响,并利用扫描电子显微镜( SEM)和接触角测量仪表征了复合膜的结构.结果表明,PEG600-LiCl、丙酮-LiCl、丙三醇-LiCl和PVP-LiCl 4种混合添加剂均可以改善膜性能,其中PEG600-LiCl、丙三醇-LiCl、PVP-LiCl3种混合添加剂加到铸膜液中,明显改善了PVDF膜表面的亲水性,可以将膜表面接触角降低至55°.当PVP与LiCl的质量比为1∶2时,膜的性能达到最优,孔隙率为82.5％,平均孔径为0.1 μm,水通量为100.5 L·m-2·h-1,截留率为95.4％.     

纳米SiO2粒子填充PMMA体系的流变性能

考察了温度和纳米二氧化硅(SiO2)粒子含量对聚甲基丙烯酸甲酯(PMMA)/SiO2复合体系动态流变行为的影响.结果表明,不同温度下随着纳米SiO2粒子含量的增加复合体系均呈现弹性模量(G')、损耗模量(G')逐渐增加而损耗角正切(tanδ)逐渐减小的趋势.当纳米SiO2粒子含量较低即小于6%(体积分数,下同)时,复合体系在低频率下(0.01～0.10 rad/s)的G'呈现随温度(190～210℃)增大而减小的正常行为;当纳米SiO2粒子含量超过6%时,复合体系在低频率下的G'随温度升高反而增大,而且此时tanδ出现显著的峰值和谷值.高填充体系中粒子在较高温度下活动性的提高以及粒子团聚结构的生成是复合体系在低频率区域弹性响应增大的可能原因.     

PVDF/TiO2杂化纤维膜的制备及其性能分析

采用静电纺丝的方法制备聚偏氟乙烯（PVDF）/二氧化钛（TiO2）杂化纤维膜,并利用扫描电子显微镜、X射线衍射仪和可见分光光度计等仪器对杂化纤维膜的微观形貌、晶体结构、力学性能以及光催化性能进行研究与分析。结果表明,随着TiO2添加量的增加,PVDF/TiO2杂化纤维膜表面暴露的TiO2增加;杂化纤维膜的拉伸强度呈现先增后减的趋势;且杂化纤维膜的光催化降解能力逐渐增强;同时PVDF/TiO2杂化纤维膜具有良好的重复利用性。     

VGCF填充PVDF/PMMA复合材料导电性能的研究

以气相生长碳纤维（VGCF）为导电填料,聚偏氟乙烯（PVDF）、聚甲基丙烯酸甲酯（PMMA）为基体制备复合型导电高分子材料。考察了填料用量、基体种类、配比以及PVDF结晶行为对复合材料导电性能的影响。结果表明,VGCF填充PMMA、PVDF、PVDF／PMMA（50／50）体系的渗滤阔值分别为5、4、3phr的填料用量。VGCF的加入会导致PVDF／PMMA体系发生微观相分离,而且VGCF会选择性富集在PVDF的非晶相中,所以PVDF／PMMA／VGCF体系的导电性呈现双重渗滤现象,该体系的体积电阻率不仅取决于富集相中VGCF的含量,而且还与PVDF相的连续性及其结晶行为密切相关。     

Formation of core/shell ultrafine fibers of PVDF/PC by electrospinning via introduction of PMMA or BTEAC

Core/shell structured ultrafine fibers of poly(vinylidene fluoride) (PVDF)/polycarbonate (PC) were prepared by electrospinning their dispersions in a mixed solvent of N,N-dimethylformamide and tetrahydrofuran. The morphology of the obtained fibers viewed under a scanning electron microscope and a transmission electron microscope could be adjusted via introduction of poly(methyl methacrylate) (PMMA) or triethylammonium chloride (BTEAC). The viscosity of the dispersions increased with the increasing amount of PMMA in the range of 10-15 wt%, while the diameter of the dispersive spheral phase in the dispersions decreased. A proper amount of PMMA could decrease the resistance of the dispersive phase transformation in PVDF/PC dispersions, so that the uniform fibrous morphology and distinct core/shell structure were easily formed in the electrospun fibers. Because of the significant increase of the conductivity of the PVDF/PC dispersion, addition of 2 wt% BTEAC could also promote formation of the core/shell structure of electrospun PVDF/PC ultrafine fibers. Comparison between electrospun fibers of PVDF/PC, PVDF/PC/PMMA and PVDF/PC with BTEAC etched by chloroform showed that the core/shell structure of PVDF/PC with BTEAC was in the highest quality.     

熔融模压制备PVDF/石墨烯复合材料及其性能研究

以聚偏二氟乙烯(PVDF)树脂为基体、石墨烯为填料,通过高速混合机混合作用,经分散剂、润湿剂、表面活性剂、相容剂等组分协同作用,使石墨烯在PVDF中分散均匀,然后经熔融模压成型,制得PVDF/石墨烯复合材料。利用扫描电子显微镜和透射电子显微镜研究了复合材料的微观形貌,并研究了石墨烯含量、制备工艺、助剂及PVDF树脂牌号对复合材料介电性能、导电性能和导热性能的影响。结果表明,采用的助剂体系和高速混合、熔融模压的制备方法能使石墨烯以微片的形态均匀地分散在PVDF树脂基体中,形成良好的功能网络结构;复合材料介电常数、电导率、介电损耗、体积电阻率和导热系数均随石墨烯含量增加而增大;当石墨烯质量分数达到2.0%左右时,复合材料的介电和导电特性均发生突变,向高介电、高导电材料转变,而当石墨烯质量分数达到5.0%左右时,复合材料开始向高导热材料转变;制备工艺和PVDF树脂牌号对复合材料热、电性能的影响则相对较小。     

Effect of salt additive on the formation of microporous poly(vinylidene fluoride) membranes by phase inversion from LiClO4/Water/DMF/PVDF system

The effect of a salt additive, lithium perchlorate, on the morphology and crystal structure of PVDF membranes prepared by wet phase inversion process was studied. The gelation phase boundaries of the quaternary system, LiClO4/water/DMF/PVDF, were determined at 25 °C. It was found that the gelation lines shifted up progressively with increasing salt contents in this system. For a salt-free casting dope, the formed membrane exhibited a typical asymmetric structure characterized by the skin, parallel columnar macrovoids, and cellular pores. WAXD analysis indicated that PVDF crystallized into ‘α’ (type II) structure in this membrane. By contrast, when PVDF was precipitated from high salt-content dopes (e.g. ≥5 wt%), the macrovoids bent and extended towards the bottom region while the original cellular pores evolved into very large voids. The PVDF crystallites became ‘β’ form (type I) in these membranes. Thermal analysis (DSC) of all membranes showed dual melting peaks at low heating rates (≤5 °C/min), suggesting that the crystallites formed in the immersion-precipitation process were imperfect and they underwent re-crystallization during the heating process. Using low voltage SEM at high magnifications (e.g. 100 KX at 0.55 KV) on uncoated samples, the fine structures (10-20 nm) of the PVDF crystallites were observed. And at very high magnifications (225 KX at 0.59 KV), it was observed that the skin region of the membrane prepared from high salt-content dopes actually contained many nano-pores (e.g. 20 nm). This contributes to the high permeation rate and low solute rejection as revealed from the water-flux measurements.     

Novel polymer composites of RuO2@nBaTiO3/PVDF with a high dielectric constant

The dielectric properties of a novel polymer dielectric material were investigated. The conductive phase of RuO₂ was synthesized for deposition on the surface of a nanosized BaTiO₃ (nBT). The RuO₂@nBT hybrid particles were incorporated into a poly (vinylidene fluoride) (PVDF) as a three-phase composite (RuO₂@nBT/PVDF). The obtained dielectric constant (ε′) was significantly high (3837.16) for the composite with a volume fraction of $f_{Ru{O}_2@nBT}$ = 0.50. The large interfacial polarization between the RuO₂?nBT and RuO₂?PVDF interfaces considerably increased the value of ε′. Therefore, interfacial polarization is a critical factor in improving the dielectric properties. The dielectric behavior of the RuO₂@nBT/PVDF composites can be described using the effective medium percolation theory model, which indicates the significant contributions of the conductive RuO₂ phase and high-permittivity nBT phase.     

Cooperative effect of shear and nanoclay on the formation of polar phase in poly(vinylidene fluoride) and the resultant properties

The polar crystalline phase is the most important crystal mode for poly(vinylidene fluoride) (PVDF); its high content is urgently desired in the large-scale processing fabrication likes injection-molding. In this study, we proposed a convenient pathway to achieve large amount of polar phase in injection-molding part through cooperation of exerting oscillatory shear field and adding nanoclay. The effects of these two factors on the polymorphic composition were well demonstrated by infrared spectroscopy and X-ray diffraction. The increment of polar phase content was limited when shear field was solely imposed or only less amount of nanoclay, 1 wt%, was added. Whereas, by simultaneously exerting shear field and adding 1 wt% nanoclay, an extremely high polar phase fraction was achieved. So a positive cooperative effect of shear and nanoclay on the formation of polar phase can be proved absolutely. The simultaneously exerting shear and adding nanoclay leaded to not only high content of polar phase but also highly oriented structure. With this unique structure, an order-of-magnitude increase in the ductility (elongation) as well as good piezoelectric property has been achieved for the molded parts of PVDF/nanoclay nanocomposites.     

聚偏氟乙烯/有机累托土纳米复合超滤膜的制备、表征和性能研究

用溶液插层法制备了聚偏氟乙烯(PVDF)/有机累托土(OREC)纳米复合超滤膜,研究了OREC含量对复合膜力学性能、表面粗糙度、微观形貌、结晶行为和亲水性的影响,并测定了复合膜的性能。结果表明:OREC的加入对复合膜微观形貌有重要影响,使膜的孔隙率从44.6%增加至71.3%;OREC的加入有利于PVDF中亲水性β相的生成,在其含量较高时能显著提高复合膜的表面粗糙度和表面亲水性,并能同时提高复合膜的纯水通量和蛋白截留率;刚性OREC片层的加入,能显著改善复合膜的力学性能,对弹性模量的增强尤为明显,可达纯PVDF膜的5.8倍。     

Thermal conductivity of PVDF/PANI-nanofiber composite membrane aligned in an electric field

Poly(vinylidene fluoride)(PVDF) is a semi-crystalline thermoplastic polymer with excellent thermal stability,electrochemical stability and corrosion resistance, which has been widely studied and applied in industrial nonmetallic heat exchanger and piezoelectric-film sensor. In this study, polyaniline(PANI) nanofibers were synthesized using dodecylbenzene sulfonic acid as the surfactant. The obtained PANI nanofibers were blended in PVDF matrix to enhance thermal conductivity and tensile strength of composite materials. Electric field was applied for the orientation of membrane structure during membrane formation. Scanning electron microscope(SEM) images exhibited that the PANI nanofibers were well-dispersed in the composite membranes. The structure of composite membranes was more orderly after alignment. X-ray diffraction(XRD) and differential scanning calorimetry(DSC) indicated that the content of PANI nanofibers contributed to the transformation of PVDF from α-phase to β-phase. Both the tensile strength and thermal conductivity of composite membranes were significantly improved. This tendency was further enhanced by the application of electric field. The maximum tensile strength was obtained when the content of PANI nanofibers was 3 wt%, which was 46.44% higher than that of pure PVDF membrane. The maximum thermal conductivity of composite membranes after alignment was 84.5% greater than that of pure PVDF membrane when the content of PANI nanofibers was 50 wt%. The composite membrane is a promising new potential material in heat transfer field and the mechanism explored in this study would be informative for further development of similar thermal conductive polymeric materials.     

紫外接枝丙烯酸对PVDF膜表面改性的研究

以二苯甲酮为光引发剂,通过紫外辐照将亲水性单体丙烯酸接枝于聚偏氟乙烯(PVDF)膜的表面。考察了光引发剂浓度和辐照时间对接枝率的影响,并利用衰减全反射光谱和扫描电子显微镜对接枝后PVDF膜表面的化学组成和微观形貌进行了表征。结果表明:随着光引发剂浓度的增大,丙烯酸的接枝率先增大后减小。通过纯水接触角和吸水率研究了接枝后的PVDF膜的亲水性,发现接枝后的PVDF膜的亲水性得到明显改善。