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.     

Phase-change core/shell structured nanofibers based on eicosane/poly(vinylidene fluoride) for thermal storage applications

We fabricated eicosane/poly(vinylidene fluoride) (PVDF) core/shell nanofibers by melt coaxial electrospinning as potential heat-storage applications. Eicosane, a hydrocarbon with melting point near the human body temperature and high latent heat, was chosen as the core material. Melted eicosane and PVDF solutions were coaxially electrospun using a double spinneret, in which melted eicosane was fed at 0.090–0.210 mL/h while the feeding rate of PVDF solution was maintained constant at 1.500 mL/h. The applied voltage and working distance were maintained constant at 12 kV and 17 cm, respectively. Good core/shell structure of nanofibers was observed at core feed rates of 0.090–0.180mL/h by transmission electron microscopy. Differential scanning calorimetry and thermogravimetric analysis values indicated good thermal stability and high energy-storage capacity of the obtained nanofibers. The highest amount of eicosane encapsulated in the electrospun core/shell nanofibers reached 32.5 wt% at core feed rate 0.180 mL/h and had a latent heat of 77 J/g at melting point 39.2 °C. These shape-stabilized core/shell composite nanofibers showed good thermoregulating properties and had sufficiently high tensile strength for potential energy-storage applications, especially in smart textiles.     

Supercritical CO2 assisted formation of poly(vinylidenefluoride) aerogels containing amoxicillin,used as controlled release device

In this work, a supercritical CO₂ (SC-CO₂) drying process for the formation of poly(vinylidenefluoride) (PVDF) aerogels containing amoxicillin has been tested. Experiments at pressures ranging between 150 and 250 bar and at temperatures ranging between 35 and 55 °C have been performed; then, the PVDF – isopropyl alcohol – N-methylpirrolidone solution at 10% (w/w) polymer has been selected for the addition of amoxicillin at concentrations between 10 and 30% (w/w) with respect to PVDF. Since amoxicillin is soluble in isopropyl alcohol, a quaternary solution has been obtained that produced PVDF aerogels characterized by drug coated nanometric fibers. A two step formation mechanism has been hypothesized that puts in evidence the non-interference of amoxicillin on PVDF gelation process and the heterogeneous amoxicillin precipitation on PVDF nanofibers. The coverage of nanofibers by amoxicillin turned the structure from hydrophobic to quasi-hydrophilic. A homogeneous drug distribution was obtained; a quasi-constant release rate and no burst effect were observed.     

聚偏氟乙烯/石墨烯复合材料的制备及性能研究

用溶液共混法制备出聚偏氟乙烯/氧化石墨烯复合材料(PVDF/GO),经高温热压将GO还原得到聚偏氟乙烯/还原氧化石墨烯复合材料(PVDF/rGO)。研究了填料种类及含量对复合材料电学性能、热稳定性和力学性能的影响。结果表明：随GO和rGO的添加,两种复合材料的介电常数(ε _r)均变大、介电损耗(tanδ)变化不大;低含量下GO和rGO均能提高PVDF的热稳定性,但rGO对PVDF性能的改善效果更好;随填料含量从0增加到8%(质量),100 Hz下PVDF/rGO复合材料的ε _r从3.60增加到38.30,PVDF/rGO[4%(质量)]复合材料失重率为5%的分解温度较纯PVDF提高了6.44℃。rGO增强了PVDF的刚性,PVDF/rGO复合材料的拉伸强度先增大后减小,杨氏模量逐渐增大,当rGO含量为4%(质量)时拉伸强度最大,拉伸强度和弹性模量分别较纯PVDF提高了35.30%、22.58%。但GO和rGO都降低了复合材料的击穿场强。     

Influence of fluorine interface to the crystallization of poly (vinylidene fluoride)/silicone rubber/fluororubber elastomeric tertiary blends via dynamical curing

ABSTRACT

We demonstrate the influence of fluorine interface to the crystallization of poly(vinylidene fluoride) (PVDF)/silicone rubber (SR)/fluororubber (FKM) tertiary dynamic curing blends. In contrast to PVDF/SR binary blend, the average size of PVDF spherulites turns smaller and the crystallization rate is lower in PVDF/SR/FKM tertiary blend when more fluororubber component was added into the blends at the same crystallization temperature. Incorporation of FKM does not change the crystalline form of PVDF in the blends. The resulting mechanical properties of tensile strength, flexural strength, Izod impact strength and elongation at break for PVDF/SR/FKM tertiary blends are enhanced compared with PVDF/SR binary blend.     

Coaxial electrospun nanofibers of poly(vinylidene fluoride)/polyaniline filled with multi‐walled carbon nanotubes

Core‐shell nanofibers of poly (vinylidene fluoride)/polyaniline/multi‐walled carbon nanotubes (PVDF/PANi/MWCNTs) have been produced using the coaxial electrospinning technique. The nanofibers were semiconductive and had better piezoelectric properties than pure PVDF nanofibers. Piezoelectric PVDF nanofibers are capable of converting mechanical energy into electrical energy, which can be stored in charge storage devices. However, PVDF is not conductive and therefore, a conductive associate material is needed to transfer accumulated static charges into the capacitor. Fourier Transform Infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC) were carried out to study the crystalline β‐phase of PVDF. There was an increase in β‐phase in the electrospun PVDF nanofibers filled with MWCNTs as compared with compression molded samples of neat PVDF. Incorporation of PANi as an intrinsically conductive polymer (ICP) and MWCNTs as conductive nanofiller helps the movement of static charges. Core‐shell nanofibers had conductivities of about seven orders of magnitude higher than simple electrospun nanofibers. POLYM. COMPOS., 35:1198–1203, 2014. © 2013 Society of Plastics Engineers     

Fabrication and characterization of electrolyte membranes based on organoclay/tripropyleneglycol diacrylate/poly(vinylidene fluoride) electrospun nanofiber composites

Utilizing polymer electrospinning technology, novel electrolyte membranes based on poly(vinylidene fluoride) (PVDF)/organomodified clay (OC)/tripropyleneglycol diacrylate (TPGDA) composite nanofibers with a diameter of 100–400 nm were fabricated for application in lithium batteries. Ultraviolet photo‐polymerization of electrospun PVDF/OC/TPGDA nanofibers generated chemically crosslinked TPGDA‐grafted PVDF/OC nanofibers exhibiting robust mechanical and electrochemical properties. The prepared fibrous PVDF/OC/TPGDA electrolytes were characterized in terms of morphology, crystallinity, electrochemical stability, ionic conductivity and cell cycleability. Based on differential scanning calorimetry analysis, the crystallinity of PVDF decreased by ca 10% on employing the OC and TPGDA. Compared with pure PVDF film‐based electrolyte membranes, the TPGDA‐ and OC‐modified PVDF electrolyte membranes exhibited improved mechanical properties and various electrochemical properties. The OC‐ and TPGDA‐modified microporous membranes are promising candidates for overcoming the drawbacks of the lower mechanical stability of fibrous‐type electrolytes with further improvement of electrochemical performance. Copyright © 2009 Society of Chemical Industry     

Preparation and properties of peroxide dynamically vulcanized poly(vinylidene fluoride)/silicone rubber/zinc dimethacrylate composites

Composites of poly(vinylidene fluoride) (PVDF), silicone rubber (SR), and zinc dimethacrylate (ZDMA) were prepared via peroxide dynamic vulcanization. The effect of ZDMA loading on the morphology, mechanical properties, and rheology of the PVDF/SR/ZDMA composite was investigated. It was found that, some rubber particles with different diameters were aggregated and distributed in the PVDF matrix. The average diameters of rubber particles increased when ZDMA was incorporated into the PVDF/SR blend. A higher content of ZDMA seemed to show a favorable effect on the mechanical properties of PVDF/SR/ZDMA composites. The tensile strength, flexural strength, and flexural modulus of PVDF/SR/ZDMA composites decreased with increasing the ZDMA loading, which was due to the decreased tensile strength and total crosslink density of SR/ZDMA composite and the increased diameter of rubber particles, but the compatibility and interfacial interaction between PVDF phase and SR phase were obviously improved, which contributed to improved the Izod impact strength. In addition, the rheology analysis also suggested that interfacial adhesion between PVDF phase and SR phase was improved due to the incorporation of ZDMA. POLYM. COMPOS. 37:1093–1100, 2016. © 2014 Society of Plastics Engineers     

剪切速率对乙烯-丙烯酸酯橡胶/聚偏氟乙烯热塑性硫化胶性能的影响

采用动态硫化法制备了乙烯-丙烯酸酯橡胶（AEM）/聚偏氟乙烯（PVDF）热塑性硫化胶（TPV）,考察了动态硫化过程中转子剪切速率对TPV微观相态结构及性能的影响。结果表明,动态硫化过程中转子的剪切速率越快,AEM和PVDF更易发生相转变,微观相态结构更加精细,形成具有“海-岛”结构的TPV。随转子的剪切速率加快,TPV的拉伸强度和扯断伸长率均先增大后减少。当剪切速率为75 r/min时,AEM/PVDF TPV具有较好的力学性能,拉伸强度达到14.84 MPa,扯断伸长率为246%,TPV具有更加优异的耐热油和热空气老化性能。     

Drug loaded electrospun polymer/ceramic composite nanofibrous coatings on titanium for implant related infections

Developing an effective antibacterial surface with the help of drugs that prevent bacterial adhesion, colonization, and proliferation into the surrounding tissues is of great demand. Rifampicin (Rf) is effective antibiotic drug proved has proved its potential in treating bacteria in biofilms, especially against the microbes causing bone infections. Hydroxyapatite (HA), a biocompatible osteoconductive ceramic, has been verified to be a significant material for bioactivity enhancement. Electrospinning is an effective inexpensive method for incorporating nanoparticles into nanofibers with uniform distribution for the drug delivery system for tissue engineering applications. In the current study, for improving bioactivity and antibacterial properties, novel functional polycaprolactone (PCL) composite nanofibers loaded HA and Rf was developed and coated on titanium (Ti). Different characterization techniques such as SEM, EDS, XRD, FITR were used to analyze these PCL/Rf/HA nanocomposites. The results showed that the bioactivity and tensile strength of the composite scaffold increased with the addition of HA nanoparticles. In vitro bioactivity demonstrated that the PCL/HA/Rf composite nanofibers possess enhanced calcium deposition when compared to the pure sample. Cellular interactive responses such as adhesive and proliferation were evaluated using hFOB human fetal osteoblast cell lines. After 6 days of culturing, the cellular properties on Ti sample coated with PCL/HA/Rf was significantly improved. Antibacterial evaluations on the substrates showed that Rf-loaded PCL/HA fibers displayed >3 log reduction against S.aureus MRSA, and S.epidermidis bacterial strain and >2 log reduction against P.aeruginosa bacteria. In vitro drug release study shows initial burst release of Rf, followed by sustained released of 62% at the end of 32 days. The cell viability, adhesion, and proliferation evaluation suggest that the PCL/HA/Rf coated substrate possess good cytocompatibility. Further incorporation of Rf enhanced the antibacterial property of this nanofibrous scaffold.     

Multilayered Electrospun/Electrosprayed Polyvinylidene Fluoride+Zinc Oxide Nanofiber Mats with Enhanced Piezoelectricity

Electrospun polyvinylidene fluoride (PVDF) nanofibers have been widely used in the fabrication of flexible piezoelectric sensors and nanogenerators, due to their excellent mechanical properties. However, their relatively low piezoelectricity is still a critical issue. Herein, a new and effective route to enhance the piezoelectricity of PVDF nanofiber mats by electrospraying zinc oxide (ZnO) nanoparticles between layers of PVDF nanofibers is demonstrated. As compared to the conventional way of dispersing ZnO nanoparticles into PVDF solution for electrospinning nanofiber mats, this approach results in multilayered PVDF+ZnO nanofiber mats with significantly increased piezoelectricity. For example, 6.2 times higher output is achieved when 100% of ZnO (relative to PVDF quantity) is electrosprayed between PVDF nanofibers. Moreover, this new method enables higher loading of ZnO without having processing challenges and the maximum peak voltage of ≈3 V is achieved, when ZnO content increases up to 150%. Additionally, it is shown that the samples with equal amount of material but consisting of different number of layers have no significant difference. This work demonstrates that the proposed multilayer design provides an alternative strategy to enhance the piezoelectricity of PVDF nanofibers, which can be readily scaled up for mass production.     

聚偏氟乙烯/类基体基团修饰石墨烯导热复合材料研究

采用含类基体基团的乙烯基三甲氧基硅烷修饰氧化石墨烯(GO),再用"一锅法"将其还原得到功能化石墨烯(F-GE),通过溶剂浇注法制备出界面性能优良的聚偏氟乙烯导热复合材料(PVDF/F-GE).利用红外光谱仪(FTIR)、扫描电子显微镜(SEM)、热导率测试仪、电子拉力试验机对复合材料的改性状态、微观形貌、导热性能和力学...     

纳米二氧化硅填充PVDF聚合物微孔膜的研究

以丙酮及N,N-二甲基甲酰胺为混合溶剂、聚偏氟乙烯为成膜物质、纳米二氧化硅为填料,通过溶液共混法制备了聚偏氟乙烯/二氧化硅(PVDF/SiO2)复合微孔薄膜。研究发现,溶剂组分质量比对薄膜力学性能有重要影响,当m(丙酮)∶m(N,N-二甲基甲酰胺)=19∶1时,薄膜力学性能最佳,其拉伸强度为3.26 MPa;经纳米SiO2改性后,复合薄膜力学性能随SiO2质量分数的增大先提高后降低,在w(SiO2)=20%时,薄膜拉伸强度达最大值6.36 MPa;复合薄膜孔隙率随SiO2质量分数的升高而增大,当w(SiO2)=40%时,孔隙率达最大值113.9%。     

Recycling carbon fiber from composite waste and its reinforcing effect on polyvinylidene fluoride composite: Mechanical,morphology, and interface properties

Recycled carbon fiber (RCF) was reclaimed from thermoset composite waste and employed as reinforcement from 0 to 30 wt% to prepare polyvinylidene fluoride (PVDF)/RCF composite. Commercial virgin carbon fiber (VCF) was used as comparison. The surface morphology, chemistry, and tensile properties of carbon fibers were investigated by Scanning Electron Microscopy (SEM), X‐Ray Photoelectron Spectroscopy (XPS), and tensile test. Results showed that the roughness, O/C ratio and –COO content of RCF surface were significantly improved after recycling. In addition, the single fiber tensile strength and modulus of RCF was lower than that of VCF. The interfacial adhesion between RCF and PVDF was much stronger due to the high chemical activity and roughness over the RCF surface. Mechanical properties of composites were investigated by flexural test, impact test, and Dynamic Mechanical Analysis (DMA). It is found that the PVDF/RCF composite showed higher flexural properties, storage modulus, and lower impact strength, which indicated the strong interfacial adhesion, played an important role in reinforcing. The morphology of fracture further demonstrated the strong interface in PVDF/RCF composite. The fiber length distribution and crystallinity of composites were also evaluated to characterize the composites. The work develops potential for recycling and reuse of carbon fiber, and also expands the application of PVDF based composite. POLYM. COMPOS., 38:2544–2552, 2017. © 2015 Society of Plastics Engineers     

Structure and properties of electrospun poly(vinylidene fluoride)/polycarbonate membranes after hot‐press

Poly(vinylidene fluoride) (PVDF)/polycarbonate (PC) dispersed solutions were electrospun into ultrafine core/shell fibers and modified by hot‐press. Morphology, tensile properties, porosity, and liquid absorption of the electrospun membranes as well as the crystallinity of PVDF were examined before and after hot‐press. Results showed that the tensile strength and tensile modulus of the electrospun membranes increased after hot‐press, especially when poly(methyl methacrylate) (PMMA) or benzyl triethylammonium chloride (BTEAC) was introduced for the formation of distinct core/shell fiber structure. The elongation of the hot‐pressed electrospun PVDF/PC membrane with addition of BTEAC was also significantly enhanced by reason of the clearest core/shell structure. The crystallinity of PVDF did not change too much before and after hot‐press, however the porosity and liquid absorption of the hot‐pressed electrospun membranes decreased to about 58% and around 75–90%, respectively, with no significant differences between PVDF/PC, PVDF/PC/PMMA, and PVDF/PC with BTEAC membranes. This study could be an example of electrospun membranes in multi‐polymer components and it could be extended to other systems of electrospinning for applications in filtration and so on. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Poly(vinylidene fluoride)/silica nanocomposite membranes by electrospinning

Poly(vinylidene fluoride) (PVDF)/silica nanocomposite membranes containing up to 30% silica were prepared by electrospinning using colloidal silica as the source of silica and dimethyl formamide as the solvent. The fiber morphology was observed by field emission scanning electron microscopy. The average fiber diameter is about 0.3 μm for PVDF/silica composite fibers having 10–30% silica. Silica nanoparticles were observed on all fiber surfaces with fairly good dispersion and distribution. Fourier transform infrared spectroscopy and differential scanning calorimeter were used to investigate the crystallization behavior of PVDF and showed that a mixture of α‐, β‐, and γ‐phase crystals was obtained with little content of α phase and all the PVDF/silica composite membranes have similar degree of crystallinity. Static water contact angle measurements were performed to investigate the surface wettability of the membranes. The mechanical properties were evaluated by tensile tests, showing strong reinforcement effect. The tensile modulus and tensile strength increase significantly when silica is present. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Enhanced Piezoelectric Performance of Electrospun Polyvinylidene Fluoride Doped with Inorganic Salts

A novel approach to preparing electrospun polyvinylidene fluoride (PVDF) nanofibers is proposed, with high piezoelectric performance. PVDF nanofibers are doped with inorganic salts without the use of any postpolarization treatment. Twenty‐six salts are doped into the nanofibers and their piezoelectric properties are studied. The salts are classified into three groups based on their differing piezoelectric enhancement effects. A piezoelectric nanogenerator fabricated with an optimized electrospun PVDF nanofiber mat shows a piezovoltage seven times greater than that of a device based on undoped nanofibers. The simple and low‐cost approach to fabricate these piezoelectric nanofiber mats may broaden the range of industrial applications of these materials in energy‐harvesting devices and portable sensors.     

界面增强型PVDF/PET膜的制备及性能

通过对支撑材料进行表面改性处理和浸入凝胶法制备了界面增强型聚偏氟乙烯/聚对苯二甲酸乙二醇酯（PVDF/PET）超滤膜。用电导率在线测量法确定了硅烷偶联剂 3-氨丙基三乙氧基硅烷（KH550）水解液的制备条件,考察了改性处理条件对PVDF/PET膜的界面性能和力学性能的影响。通过180°剥离试验测试PVDF膜与支撑层间的剥离强度,用扫描电镜观察PET无纺布及PVDF膜破坏底面的微观形貌,用傅里叶红外光谱仪表征PET表面化学组成。结果表明,水解液中KH550用量较少时（≤3%）,处理时间延长,PVDF/PET间的剥离强度增大,水解液中KH550用量较多时（>3%）,处理时间延长,PVDF/PET间的剥离强度先增大后减小;PVDF/PET膜的拉伸强度随水解液中KH550用量的增加或处理时间的延长先增大后略减小。改性前后PVDF/PET膜的分离与透过性能对比表明,PET表面改性后,PVDF膜的牛血清白蛋白（BSA）截留率几乎不受影响,水通量略增。     

Simultaneously improving thermal conductivity and dielectric properties of poly(vinylidene fluoride)/expanded graphite via melt blending with polyamide 6

Poly(vinylidene fluoride)/polyamide 6/expanded graphite (PVDF/PA6/EG) composite is prepared via one-step melt extrusion. The EG is well dispersed with the addition of PA6 and mainly distributed in the PA6 phase due to the stronger affinity between them. As a result, the PVDF/PA6/EG sample presents higher dielectric permittivity than the PVDF/EG sample and maintain a low dielectric loss due to its sea-island phase structure, which impedes the formation of conductive path in the composite. The mean interlayer spacing of the EG in the polymer matrix decreases obviously due to its improved dispersion state, which is in favor of the phonon transportation in the composite. As a result, the PVDF/PA6/EG sample exhibits a significantly improved thermal conductivity of about 0.48 W m⁻¹ K⁻¹, which is 140% higher than that of the PVDF sample and 37% higher than that of the PVDF/EG sample. Moreover, the PVDF/PA6/EG sample presents higher Young's modulus and tensile strength than the PVDF/EG sample. While the elongation at break of the PVDF/PA6/EG sample is only a little lower than that of the PVDF/EG sample. This means that the tensile properties of the composite are not destroyed obviously by melt blending with the immiscible PA6.     

Toughened electrospun nanofibers from crosslinked elastomer‐thermoplastic blends

A crosslink‐able elastomeric polyester urethane (PEU) was blended with a thermoplastic, polyacrylonitrile (PAN), and electrospun into nanofibers. The effects of the PEU/PAN ratio and the crosslinking reaction on the morphology and the tensile properties of the as‐spun fiber mats were investigated. With the same overall polymer concentration (9 wt %), the nanofiber containing higher composition of PEU shows a slight decrease in the average fiber diameter, but the tensile strength, the elongation at break and tensile modulus of the nanofiber mats are all improved. These tensile properties are further enhanced by slight crosslinking of the PEU component within the nanofibers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007