VB_2/SiO_2/PVDF复合材料压电薄膜的性能研究

介绍了维生素B_2/二氧化硅/聚偏氟乙烯(VB_2/SiO_2/PVDF)复合材料薄膜的制备工艺和压电性能。研究发现,在PVDF溶液中添加VB_2粉末和纳米SiO_2颗粒,通过蒸发结晶制备成膜,采用高倍率单轴拉伸和高压极化的方法可增加复合材料中β相的含量,从而提高复合材料的压电性能。研究中分别使用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、傅里叶红外光谱仪(FTIR)等方法对VB_2/SiO_2/PVDF薄膜进行测试,并基于悬臂梁振动平台对压电复合薄膜的性能进行了测试,分析了VB_2和SiO_2不同含量组合和悬臂梁振幅对开路电压的影响。结果表明,VB_2和SiO_2的含量同时为1%和1%时,复合材料薄膜的压电性能最优,其在1 000μ应变下可产生1.52 V的峰-峰值电压。     

多壁碳纳米管官能化对PVDF结晶行为的影响

采用溶液共混结合溶剂蒸发法制备了聚偏氟乙烯(PVDF)/多壁碳纳米管(MWCNTs)复合薄膜。研究了MWCNTs表面羟基化(MWCNTs-OH)、羧基化(MWCNTs-COOH)、氨基化(MWCNTs-NH_2)以及接枝聚甲基丙烯酸甲酯(PMMA)(MWCNTs-g-PMMA)后对PVDF结晶行为的影响。结果表明:官能化前后的MWCNTs均可提高PVDF的β晶型相含量,复合薄膜的熔融温度、结晶温度、结晶度和结晶速度均得到提高。其中含MWCNTs-g-PMMA的复合薄膜中β相含量最高,晶核密度最大,晶体尺寸较小,而结晶度有所降低,但总体都高于纯PVDF;由于MWCNTs-NH_2的氨基与PVDF分子链之间的相互偶极作用和氢键协同影响,对PVDF的结晶促进作用最为明显。     

聚偏氟乙烯/石墨烯发泡复合材料制备及电磁屏蔽性能

使用熔融共混的方法制备不同含量石墨烯纳米片(GNPs)的聚偏氟乙烯(PVDF)复合材料,并采用超临界二氧化碳作为发泡剂对其进行釜压发泡,制备PVDF复合材料泡沫.研究了PVDF复合材料的断面结构、结晶行为、熔融行为、流变行为和发泡行为,并研究了PVDF复合材料及其泡沫的电导率和电磁屏蔽性能.结果表明,GNPs质量分数为...     

共混型PVDF/TPU复合材料的制备与性能研究

为了改善热塑性聚氨酯(TPU)的力学性能及形状记忆性能,采用聚偏氟乙烯(PVDF)为共混改性剂,并经熔融共混法制备了不同PVDF含量的PVDF/TPU复合材料。采用傅里叶红外光谱分析、X射线衍射、扫描电子显微镜、拉伸和形状记忆测试等表征了所得复合材料的微观结构及性能。结果表明,PVDF与TPU间通过氢键形成了强相互作用。PVDF的加入促进了TPU的结晶。与纯TPU相比,PVDF/TPU复合材料的定伸应力升高。加入PVDF后,PVDF/TPU复合材料的形状固定率升高,形状回复率降低。综合拉伸和形状记忆测试结果,当PVDF的质量分数为5%时,PVDF/TPU复合材料的性能最佳。     

再生PVDF/蒙脱土纳米复合材料制备与性能

通过新型非对称双螺杆挤出机制备再生聚偏氟乙烯(PVDF)/蒙脱土(MMT)纳米复合材料,采用傅里叶变换红外光谱仪、差示扫描量热仪、热重分析仪、扫描电子显微镜(SEM)、转矩流变仪和万能电子试验机等对材料进行表征测试,研究MMT含量对复合材料结构和性能的影响。结果表明,MMT对复合材料的结晶行为有一定的影响,添加MMT后复合材料的熔融温度、结晶温度和结晶度都有提高,添加1% MMT复合材料的熔融温度和结晶温度分别比未加MMT的再生PVDF提高1℃和0.94℃;再生PVDF/MMT复合材料的降解温度随着MMT含量增加而降低,失重50%的温度反而随MMT含量增加而升高;SEM发现,MMT以100～200 nm的片状分散在PVDF基体中,随着MMT含量增加,出现MMT团聚、脱落现象;在实验范围内,随着MMT含量的增加,复合材料的拉伸强度和缺口冲击强度随之提高,添加5% MMT复合材料的拉伸强度比未添加MMT的提高33.5%,缺口冲击强度提高29.7%;转矩流变实验发现,适量的MMT增加了复合材料加工时的剪切作用,降低了熔体塑化平衡扭矩。     

钛酸钡对聚偏氟乙烯晶体结构和热电性能的影响

采用简单的溶液浇铸法制备了不同钛酸钡(BT)含量的聚偏氟乙烯(PVDF)纳米复合薄膜,研究了薄膜的微观结构和薄膜中所含晶体的晶型,重点研究了BT对PVDF热电性能的影响。透射电镜分析结果表明钛酸钡在聚偏氟乙烯中分散良好,傅立叶变换红外光谱仪(FTIR)和X射线衍射仪(XRD)均证实BT的加入能够诱使PVDF的其他晶型向β晶型转变,同时多功能电表测定的数据表明,BT的加入提高了PVDF的电导率和Seebeck系数。加入BT后,复合材料的热分解温度比纯PVDF略有提高。以上研究结果为BT/PVDF复合材料在热电领域的应用打下了基础。     

蒙脱土诱导聚偏氟乙烯极性相的形成及其结晶过程

用溶液共混法制备了聚偏氟乙烯/蒙脱土(PVDF/MMT)纳米复合薄膜,用红外光谱法和差示扫描量热法表征了其结晶构象和结晶度,结果表明MMT的加入能够有效诱导PVDF的极性相形成。用扫描电子显微镜观察了薄膜中MMT的分散情况,当MMT含量为0.5%时,MMT在PVDF基体中以少量晶片层的复合体或单个片层的剥离形式存在,而MMT含量为1%时,MMT在基体中大部分以较大的团聚体形式存在。MMT的片层表面与PVDF分子链之间的离子–偶极子相互作用诱导了其极性相产生,因此MMT片层与PVDF基体接触面积较大时,极性相含量更高。用偏光显微镜原位观察复合薄膜的等温结晶过程,发现MMT分散情况较好时α相晶体的成核和生长受到抑制,而γ相晶体的成核和生长受到促进。     

太阳能电池封装用PVDF/PMMA共混薄膜的表面形态及组成研究

将聚偏氟乙烯(PVDF)粉末与聚甲基丙烯酸甲酯(PMMA)颗粒物理共混后采用熔融挤出的方法制备成共混薄膜。通过差示扫描量热、X射线衍射、原子力显微镜和X射线光电子能谱等方法研究了PVDF/PMMA共混薄膜表面一定范围内的形态和组成。研究发现,PVDF与PMMA具有良好的相容性,两者间的相互作用阻碍了PVDF在共混体系中的结晶,并通过红外吸收光谱证明了类氢键的存在。PVDF在共混体系中可以发生明显的表面富集现象,表面自由能低的PVDF在表面相的含量大于体相。     

增容剂对PVDF/PUR-T复合材料的性能影响

采用流延成膜法制备了硅烷偶联剂KH–560和端氨基液体丁腈橡胶(ATBN)协同改性的聚偏氟乙烯(PVDF)/聚醚型热塑性聚氨酯弹性体(PUR–T)复合材料,初步探讨了单一增容剂(KH–560或ATBN)含量、复配增容剂含量与比例及成膜温度等条件对PVDF/PUR–T复合材料力学性能的影响,深入研究了复合材料的结晶性能、热稳定性能和亲/疏水性能。结果表明,与单一增容剂相比,复配增容剂的引入明显提高了复合材料的力学性能,并且当复配增容剂添加量为10%,复配比KH–560/ATBN=3/1,成膜温度为50℃时,其与PVDF/PUR–T基体间的界面粘结性明显得到改善,改性后复合材料断裂伸长率达到273%。PUR–T与复配增容剂的加入抑制了PVDF的结晶,复合材料的结晶度降低,但仍具有良好的热稳定性能,且疏水性得到提高。     

聚偏氟乙烯β相形成的研究进展

针对通常的熔融加工过程中聚偏氟乙烯(PVDF)结晶经常获得不具有压电性的α晶的情况,讨论了制备富含具有良好压电性能β晶的PVDF制品的方法,从纯PVDF,PVDF纳米复合材料,PVDF共混物等方面综述了制备β相PVDF的方法、影响β相含量因素及各种制备方法的利弊,并对其制备方法的趋势进行了展望。     

Improving the dielectric performance of poly(vinylidene fluoride)/polyaniline nanorod composites by stretch‐induced crystal transition

The introduction of conductive polyaniline (PANI) can significantly improve the dielectric constant of polymer‐based materials. However, there is a drawback of high dielectric loss. Herein, a simple and efficient stretching process was applied to improve the dielectric performance of poly(vinylidene fluoride)/PANI (PVDF/PANI) nanorod films through the stretch‐induced crystal transition from non‐polar α‐crystal to polar β‐crystal in PVDF and the oriented distribution of PANI nanorods. XRD, DSC and Fourier transform IR analyses indicate that the stretched PVDF and stretched PVDF/PANI films possess a high content of β‐crystal at the stretching temperature of 135 °C under a stretching ratio of 200%–400%. Furthermore, the stretched PVDF/PANI film with 10 wt% PANI displays a high dielectric constant of 338 at 100 Hz, which is increased by 20% compared to non‐stretched PVDF/PANI film (281). More importantly, the corresponding dielectric loss is reduced from 0.31 for the non‐stretched film to 0.17 for the stretched film. © 2018 Society of Chemical Industry     

High dielectric constant polyaniline/epoxy composites via in situ polymerization for embedded capacitor applications

Polyaniline (PANI)/epoxy composites with different polyaniline (PANI) contents were successfully developed by in situ polymerization of aniline salt protonated with camphorsulfonic acid within epoxy matrices and fully characterized. The influence of PANI loading levels on various properties was also explored. Dielectric and electrical properties of PANI/epoxy composites were studied for samples in parallel plate configuration. A PANI/epoxy composite prepared in this fashion reached a high dielectric constant close to 3000, a dielectric loss tangent less than 0.5 at room temperature and 10 kHz. The hardener type was also found as a critical parameter for the dielectric properties of PANI/epoxy composites. The distribution of the conductive element clusters within the polymer matrix was studied by SEM and correlated to the dielectric behavior of the composite films.     

Polyvinylidenefluoride/Polymethylmethacrylate/Polyphosphazene/Lithium Tantalate Composites: Synthesis and Characterization

This study presents the preparation of poly vinylidene fluoride (PVDF) based polymethyl methacrylate (PMMA), Poly(bis(4-Aminophenoxy)phosphazene)(PPZ) and lithium tantalate (LT) composites films using solution blending process. The fabricated PVDF/PMMA/PPZ/LT composite films were evaluated using Fourier transformed infrared spectroscopy, Scanning electron microscopy, Differential scanning calorimetry and Thermo gravimetric analyses. The changes in microstructure, dielectric, morphological and thermal properties of these films with change in composition of PVDF/PMMA/PPZ/LT have been investigated. The high PMMA content and incorporation of LT favored the PVDF phase transition from ‘α’ to ‘β’ phase as shown by FT-IR analysis. The LT particles were properly dispersed in PVDF/PMMA/PPZ matrix as confirmed by scanning electron micrograph images. The dielectric properties of the PVDF/PMMA/PPZ improved with increasing the concentration of LT. The dielectric constant of the films increased with increase in LT content in the blends. The values of dielectric properties observed were higher at lower frequency at room temperature. The composites having 10, 20, 30 & 40% LT in blend samples showed regular increase in T_ons, T_max and corresponding char yield with increase in the filler content. All the composites demonstrated two steps decomposition due to the interaction of filler with polymers at high temperature leading to oxidative decomposition of polymeric chains.     

Molecular composites obtained by polyaniline synthesis in the presence of p‐octasulfonated calixarene macrocycle

Polyaniline (PANI) molecular composites were synthesized by chemical oxidative polymerization of the aniline and aniline dimer, N‐phenyl‐1,4‐phenylendiamine, in the presence of a macrocycle, calix[8]arene p‐octasulfonic acid (C8S), using ammonium peroxidisulfate as oxidant. The macrocycle has acted both as acid dopant and surfactant to obtain processable PANI‐ES. The PANI/calix[8]arene p‐octasulfonic acid composite was also obtained by a simple doping of PANI emeraldine base form with calix[8]arene sulfonic acid. The structure of materials was confirmed by Fourier transform infrared, UV–vis and nuclear magnetic resonance spectroscopy. All synthesized composite materials are amorphous and soluble in chloroform, dimethylsulfoxide, NMP, showing excellent solution‐processing properties combined with electrical conductivity. Cyclic voltammetry evidenced a good electroactivity for the composite films. Dielectric properties (dielectric constant and dielectric losses) were determined and are comparable with those of other PANI/ionic acid polymer composites. Preliminary studies have evidenced a high dielectric constant (10⁴ at 100 Hz) and electrical conductivity of 6 × 10^?3 S/cm for PANI composites. From sulfur elemental analysis of the PANI/calixarene, it results that the content in macrocycle is ～30% (weight). © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Enhanced dielectric properties of poly(vinylidene fluoride)–surface functionalized BiFeO3 composites using sodium dodecyl sulfate as a modulating agent for device applications

In this work, we prepared a series of poly(vinylidene fluoride) (PVDF)–surface functionalized BiFeO₃ (h‐BFO)–Sodium dodecyl sulfate (SDS) composite films by solvent casting method to investigate the effect of SDS in the composites. The X‐ray diffraction confirmed that the structure of h‐BFO significantly changed in the PVDF‐(h‐BFO)‐SDS composite in comparison with the rhombohedral structure of pure BiFeO₃. The microscopic study illustrated that the composite with a higher percentage of SDS content facilitated the dispersion as well as proper distribution of ceramic particles in the polymer matrix. The presence of different functionalities of respective polymer and the modified fillers was confirmed by FTIR Spectrophotometer. The dielectric and electrical study done by Impedance Analyzer revealed that the SDS treated surface functionalized composites showed relatively higher dielectric properties than that of two phase composites and pure polymer. Finally, the ferroelectric properties of the composite films done by P‐E loop tracer revealed that the SDS‐treated composites showed an enhanced remanent polarization. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45040.     

Preparation and properties of β‐phase graphene oxide/PVDF composite films

We report preparation of graphene oxide (GO) from expanded graphite (EG) via a modified Hummers method. GO/PVDF composites films were obtained using solvent N, N‐Dimethylformamide (DMF) and cosolvent comprising deionized water/DMF combination. X‐ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses revealed that the main crystal structure of the composite films is β‐phase, and use cosolvent method tends to favor the formation of β‐phase. Scanning electron microscopy (SEM) was used to investigate the microstructure of composite films. Storage modulus and loss modulus were measured by Dynamic mechanical analysis (DMA). Broadband dielectric spectrum tests showed an increase in the dielectric constant of the GO/PVDF composite films with the rising content of GO, and by cosolvent method could improve the dielectric constant while reducing the dielectric loss. Our method that uses GO as an additive and deionized water/DMF as the cosolvent provides a promising and low‐cost pathway to obtain high dielectric materials. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41577.     

Novel dielectric behaviors in PVDF‐based semiconductor composites

Composites of polyvinylidene fluoride (PVDF) filled with different conductive fillers as carbon black (CB), nickel (Ni), zinc (Zn), and tungsten (W), respectively, were prepared at same processing condition. The temperature dependence of dielectric behaviors of composites was studied at wide filler concentration and wide frequency ranges. Results show that there are giant dielectric constants as the concentration of filler is near the percolation threshold. The dielectric constants of all studied composites decrease slowly with increasing of frequency and rise gradually with increasing filler contents in the composites. Two relaxation peak regions of dielectric constant are observed from ?30 to 40°C and from 100 to 150°C, which can be attributed to the contribution of polar effect of PVDF. The CB filled PVDF (CB/PVDF) composites present a lower percolation threshold than other metallic‐filler filled PVDF composites. The maximal dielectric constant was found in the Ni filled PVDF (Ni/PVDF) composite. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

COOH?MWCNTs‐induced BiFeO3‐poly(vinylidene fluoride) (PVDF) composites with enhanced dielectric and ferroelectric properties

In this work, flexible three phase composite films were prepared with surface functionalized multi‐walled carbon nanotubes (f‐MWCNTs) and bismuth ferrite (BiFeO₃;BFO) particles embedded into the poly(vinylidene fluoride) (PVDF) matrix via solution casting technique. The properties and the microstructure of prepared composites were investigated using an impedance analyzer and field emission scanning electron microscope. The micro‐structural study showed that the f‐MWCNTs and BFO particles were dispersed homogeneously within the PVDF matrix, nicely seated on the floor of the f‐MWCNTs separately. The dielectric measurement result shows that the resultant composites with excellent dielectric constant (≈96) and relatively lower dielectric loss (<0.23 at 100 Hz). Furthermore, the percolation theory is explored to explain the dielectric properties of the resultant composites. It says that the percolation threshold of f_MWCNTs = 0.9 wt % and the enhancement of the dielectric constant of the composite was also discussed. In addition, the remnant polarization of the un‐poled PVDF‐BFO‐f‐MWCNTs composites (2P_r ～1.34 µC/cm² for 1.1 wt % of f‐MWCNTs) is also improved. These three phase composites provide a new insight to fabricate flexible and enhanced dielectric properties as a promising application in modern electrical and electronic devices. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46002.     

COOHMWCNTs‐induced BiFeO3‐poly(vinylidene fluoride) (PVDF) composites with enhanced dielectric and ferroelectric properties

In this work, flexible three phase composite films were prepared with surface functionalized multi‐walled carbon nanotubes (f‐MWCNTs) and bismuth ferrite (BiFeO₃;BFO) particles embedded into the poly(vinylidene fluoride) (PVDF) matrix via solution casting technique. The properties and the microstructure of prepared composites were investigated using an impedance analyzer and field emission scanning electron microscope. The micro‐structural study showed that the f‐MWCNTs and BFO particles were dispersed homogeneously within the PVDF matrix, nicely seated on the floor of the f‐MWCNTs separately. The dielectric measurement result shows that the resultant composites with excellent dielectric constant (≈96) and relatively lower dielectric loss (<0.23 at 100 Hz). Furthermore, the percolation theory is explored to explain the dielectric properties of the resultant composites. It says that the percolation threshold of f_MWCNTs = 0.9 wt % and the enhancement of the dielectric constant of the composite was also discussed. In addition, the remnant polarization of the un‐poled PVDF‐BFO‐f‐MWCNTs composites (2P_r ～1.34 µC/cm² for 1.1 wt % of f‐MWCNTs) is also improved. These three phase composites provide a new insight to fabricate flexible and enhanced dielectric properties as a promising application in modern electrical and electronic devices. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46002.     

Effects of surface and volume modification of poly(vinylidene fluoride) by polyaniline on the structure and electrical properties of their composites

The structure and electrical properties of polyaniline (PANI) modified poly(vinylidene fluoride) (PVDF) films have been studied depending on the type of modification (surface or volume) and the type of dopant (HCl or dodecylbenzenesulfonic acid). The structure was studied with differential scanning calorimetry, atomic force microscopy and Raman spectroscopy (including the surface enhanced mode—SERS) techniques. Surface modification of PVDF with PANI creates a two-dimensional (2D) conductive network on the surface of PVDF films with the thickness of approximately 8 μm. The network is characterized with non-linear current voltage (I-V) characteristics and enhanced conductivity at elevated temperatures (up to 160 °C), which is opposite to volume modified samples behaviour. Conductivity of the composite films varies in the range of 10⁻⁸ to 10⁻³ S/cm depending on the preparation conditions. The observed non-linear conductivity is explained by formation of the surface conductive network of PANI alternated with β-crystalline PVDF microdomains.