预辐照接枝丙烯酸、苯乙烯磺酸钠对聚全氟乙丙烯膜性能的影响

采用常温下γ射线预辐照引发接枝的方法,在聚全氟乙丙烯(FEP)上接枝了丙烯酸(AA)和对苯乙烯磺酸钠(SSS),制备了一种含羧酸基团和磺酸基团的接枝膜.傅立叶变换红外光谱(FT-IR)分析证明了磺酸基团和羧酸基团的成功引入.采用XRD、TGA和接触角研究了接枝率对FEP膜的结晶度、热学特性及亲水性等性能的影响.结果表明,随着制备的FEP膜接枝率的增加,膜的结晶度、热稳定性和接触角逐渐减小;与此相反,FEP膜的亲水性能随接枝率的增加而增加.接枝膜湿敏性能测定结果表明,在相对湿度从5%RH变化到98%RH时,接枝膜电阻线性变化范围接近3个数量级,具有响应速度快(吸附<1min,解吸<2min),湿滞小(<3%RH)的特点,具有应用于电阻型湿度传感器的广阔前景.     

聚全氟乙丙膜电子束引发预辐射接枝AA和SSS制备阳离子交换膜的研究

利用电子束引发预辐射接枝技术,在聚全氟乙丙烯(FEP)薄膜上接枝丙烯酸(AA)和对苯乙烯磺酸钠(SSS),制备一种含羧酸基团和磺酸基团的阳离子交换膜,详细研究了反应温度、单体总浓度、pH值变化、辐照气氛及添加剂对接枝率的影响规律,明确了实验条件与接枝率的对应关系。FTIR测试证明了接枝产物是全氟乙丙烯和丙烯酸、对苯乙烯磺酸钠的接枝共聚物。     

对氨基苯磺酸两步法修饰多壁碳纳米管

用混酸处理多壁碳纳米管, 利用侧壁生成的羧酸基团, 在N,N-二环己基碳酰亚胺的作用下, 使对氨基苯磺酸接枝到碳纳米管表面. 以浓硫酸为磺化剂, 室温下制备了磺化聚醚醚酮(SPEEK). 然后采用溶液共混法制备了磺化聚醚醚酮/接枝多壁碳纳米管复合膜. 采用傅立叶变换红外光谱(FT-IR)、热重分析(TGA)、透射电镜(TEM)、拉曼光谱(Raman)等技术对碳纳米管的结构和性能进行了表征. 红外谱图表明对氨基苯磺酸上的氨基与碳纳米管表面的羧基发生了反应, 生成酰胺基团. 热重曲线表明碳管表面接枝的有机基团的比重达到40%. 拉曼光谱显示处理前后碳管的I_D/I_G值变化不大, 表明碳管的石墨结构的含量基本不变. 复合膜的力学性能测试结果表明, 对氨基苯磺酸接枝的碳管可以提高膜的拉伸强度.     

PTFE辐射接枝对苯乙烯基三甲氧基硅烷制备质子交换膜

采用聚四氟乙烯(PTFE)膜室温下共辐射接枝单体p-苯乙烯基三甲氧基硅烷(StSi),之后经磺化和水解缩聚制备了含有亲水性的—Si—O—Si—交联结构和Si—OH基团的质子交换膜.研究了溶剂、吸收剂量、吸收剂量率以及单体浓度等参数对接枝率的影响,并对质子交换膜的离子交换容量(IEC)、吸水性、尺寸稳定性及电导率等性能进行了分析.结果表明,实验条件下接枝率随吸收剂量和单体浓度增加而增加,采用3mol·L-1的单体浓度减少均聚物;吸收剂量率为10～43Gy·min-1时,接枝率随剂量率变化不明显;以甲苯做溶剂可获得较高接枝率并保持膜的机械强度;IEC值、吸水性和电导率随接枝率增加而增大,是—SO3H、—Si—O—Si—交联结构和Si—OH基团共同作用的结果.接枝率72.5%时膜的IEC值为1.53mmol·g-1,高于Nafion117(0.89mmol·g-1),90℃吸水率为63%,尺寸稳定(优于Nafion117),质子电导率达1.5×10-2S·cm-1,获得了低于Nafion117的甲醇透过性,接枝率50.1%时甲醇透过系数0.82×10-6cm2·s-1.     

萘磺酸型侧链磺化聚砜质子交换膜的性能

以聚砜(PS)和自制的1,4-二氯甲氧基丁烷(BCD)为氯甲基化试剂通过Fridel-Crafts烷基反应制备氯甲基化聚砜(CPS),紧接着氯甲基与2-萘酚-6,8-二磺酸钾(NSK)试剂通过亲核取代反应制备一种萘磺酸型磺化聚砜(PS-NS),在用红外和核磁氢谱充分表征的基础上制备一系列磺酸基团键合量不同的PS-NS质子交换膜(分别为PS-NS-1,PS-NS-2,PS-NS-3)重点研究温度对质子交换膜性能的影响规律。研究结果表明:由于亲水基团与疏水主链距离较远,能够形成类似于Nafion膜的微相分离结构,使得该质子交换膜在高磺化度下仍能保持高的尺寸稳定性,同时随着温度升高,质子交换膜的吸水率、溶胀性以及质子传导率增加,PS-NS-3在25℃和85℃的吸水率为21. 3%和42. 7%,但是溶胀率仅为22. 2%和50. 3%,与商业化Nafion115膜(24. 9%和55. 0%)的性能十分接近,表现出很好的尺寸稳定性。     

TMAH改性PVDF一步接枝PSBMA质子交换膜的制备与性能

使用四甲基氢氧化铵(TMAH)液相改性聚偏氟乙烯(PVDF),以过氧化苯甲酰(BPO)为引发剂,一步将磺酸基甲基丙烯酸甲酯(SBMA)接枝到改性的PVDF上,制备了聚偏氟乙烯接枝聚磺酸基甲基丙烯酸甲酯(PVDFg-PSBMA)质子交换膜.利用傅里叶变换红外(FTIR)光谱和扫描电镜-X射线能谱(SEM-EDX)分析了膜的结构、形貌及硫元素分布情况.同时研究了不同质量分数的TMAH甲醇溶液对PVDF-g-PSBMA膜电导率和甲醇渗透率的影响.结果表明, TMAH使PVDF脱去HF产生碳碳双键且SBMA成功接枝到改性的PVDF骨架上,硫元素在膜内外分布均匀; PVDF-g-PSBMA膜的电导率和甲醇渗透率随TMAH在甲醇中质量分数的增多而增大, TMAH质量分数为20%的膜的质子电导率在20 ℃下达到0.0892 S·cm^-1,常温下的甲醇渗透率为4.04 × 10^-7cm²·s^-1;热重分析(TGA)表明,膜的热稳定性良好,耐热温度高达270 ℃.该膜作为电解质材料的直接甲醇燃料电池(DMFC)的最大功率密度达到17.06 mW·cm^-2.     

光接枝法制备新型pH开关核孔膜

用表面光接枝方法制备了具有pH开关特性的丙烯酸接枝PET核孔膜 .XPS、SEM和AFM的表征结果证明 ,接枝膜具有非对称结构 ,丙烯酸接枝层主要在膜的向光侧表面 ,膜背侧和膜孔内没有变化 .膜孔周围的接枝链在湿态下沉入膜孔 ,接枝层对膜孔顶部产生封盖 .接枝链的体积随环境pH值的不同而变化 ,从而控制接枝膜的滤过特性 .在低接枝程度时 ,接枝链体积变化对膜孔径的影响小 ,不具有pH开关特性 ,但是接枝提高了膜的亲水性 ,通量得到提高 ;接枝程度达到一定程度时 (如 0 5 %) ,膜孔径受接枝链体积变化的影响显著 ,接枝膜表现出pH开关效应 .在pH大于 5时 ,接枝膜通量恒定 ,基本不受溶液pH值影响 .当pH值小于 4时 ,膜通量随溶液酸性的增加迅速升高 .接枝膜的开关幅度JpH =2 JpH =6 8,随接枝程度的增加而增加 .膜的通量和开关幅度可以通过接枝程度来调节     

聚偏氟乙烯接枝甲基丙烯酸甲酯油水分离膜的研究

使用四乙基氢氧化铵(TEAH)液相本体改性聚偏氟乙烯(PVDF),以过氧化苯甲酰(BPO)为引发剂,将甲基丙烯酸甲酯(MMA)接枝到改性PVDF骨架上,合成聚偏氟乙烯接枝聚甲基丙烯酸甲酯(PVDF-gPMMA)共聚物,通过浸没沉淀法制备PVDF-g-PMMA亲水性油水分离膜.通过傅里叶红外光谱(FTIR)、扫描电镜(SEM)和过滤试验分析了膜的结构和性能.同时研究了TEAH浓度和改性时间对PVDF-g-PMMA膜表面接触角的影响.结果表明,TEAH使PVDF脱去HF产生碳碳双键且MMA成功接枝到改性的PVDF骨架上,膜内外孔隙分布均匀;PVDF-g-PMMA膜的接触角随着TEAH浓度的增加、改性时间的加长而减小.TEAH浓度为2.0 wt%,改性20 min制备的PVDF-g-PMMA膜,接枝率为27.1%,孔隙度为71.6%,平均孔径为78.9 nm,接触角降至55.9°,且在50 s内降为0;纯水通量提高到665.34 L/(m2·h),截留率和水通量恢复率分别达到95.6%和90.1%.与纯PVDF膜相比,PVDF-g-PMMA膜的分离性能显著提高.     

掺杂纳米SiO2的PVDF-g-PSSA质子交换膜

以聚偏氟乙烯(PVDF)为骨架, 采用溶液接枝苯乙烯磺酸, 合成了掺杂纳米SiO₂颗粒的复合质子交换膜(PVDF/xSiO₂-g-PSSA). 利用红外光谱、热失重分析方法、扫描电镜, 对膜的结构、热稳定性、表面及断面形态进行了表征. 考察了膜的吸水率、电导率、甲醇渗透性等性质. 结果表明, 纳米SiO₂颗粒能提高膜的阻醇性能, 掺杂质量分数10%的适量SiO₂颗粒所得的复合膜的甲醇渗透系数达1.0×10^－7 cm²/s, 低于聚偏氟乙烯接枝苯乙烯磺酸(PVDF-g-PSSA)膜的1.7×10^－7 cm²/s, 仅为Nafion-117的渗透系数的二十分之一. PVDF/10% SiO₂-g-PSSA复合膜具有较高的选择性, 在直接甲醇燃料电池中具有良好的应用前景.     

超亲水聚偏氟乙烯中空纤维膜的制备及性能

采用超声辅助接枝聚合技术,将甲基丙烯酸缩水甘油酯(GMA)接枝到聚偏氟乙烯(PVDF)膜表面,制备PVDF-g-GMA膜;再利用氨基诱导环氧基团发生开环反应,将苏氨酸(Thr)接枝到PVDF-g-GMA膜表面,制备了具有两性离子结构表面的PVDF-g-GMA-Thr膜。通过衰减全反射傅里叶变换红外光谱(ATR-FTIR)、X射线光电子能谱(XPS)、接触角测试仪、场发射扫描电子显微镜(FESEM)和牛血清白蛋白(BSA)过滤实验等系统研究了改性前后PVDF膜表面的化学组成、润湿性能、表面形貌和抗污染性能。研究结果表明,随着PVDF-g-GMA接枝Thr反应时间的增加,PVDF-g-GMA-Thr膜的亲水性能明显提高,接触角从90°降为0°,呈现出超亲水性能。同时PVDF-g-GMA-Thr膜的水通量明显提高,当Thr诱导开环反应时间为12 h时,PVDF-gGMA-Thr膜的水通量高达686 L/(m²·h),与PVDF原膜相比,水通量提高了204. 5%。在BSA的过滤测试中,与PVDF膜相比,PVDF-g-GMA-Thr膜呈现出良好的截留性能和抗污染性能,BS...     

A Novel Thin Film Resistive Humidity Sensor Based on Soluble Conjugated Polymer:(propionic acid)-co-(propargyl alcohol)

In recent years, humidity sensors have found wide applications in industrial and agricultural production, process control, household electric appliances, etc., therefore the research on humidity sensitive materials has attracted more and more attentions, and many polymers, including polymer electrolytes, conjugated polymers have been investigated as sensing materials1-3. However the doped conjugated polymers in general were insoluble and can not be used to prepare thin film humidity sensors, wh…     

Evaluation of co-polyaniline nanocomposite thin films as humidity sensor

Spin coated films of Co-Polyaniline nanocomposite are evaluated for their transmission properties using He-Ne laser for humidity sensing. The thickness (17-29 microm) of the films is varied by multiple deposition of Co-Polyaniline nanocomposite on a glass substrate. The samples exhibit typically two to three regions in their sensitivity curve when tested in the relative humidity (RH) range of 20-95%. The sensitivity ranges from 0.1 mV/%RH to 12.26 mV/%RH for lower to higher thickness. The sensors show quick response of 8s (20-95%RH), and a recovery time of 1 min (95-20%RH) with good repeatability, reproducibility and low hysteresis effect. The sensitivity of the sensor increases with humidity and thickness. Material characterization is done by X-ray diffraction (XRD), scanning electron micrograph (SEM) and Fourier transform infra-red spectroscopy (FTIR).     

Humidity sensors using in situ synthesized sodium polystyrenesulfonate/ZnO nanocomposites

Thin film humidity sensors have been prepared using in situ synthesized inorganic/organic nanocomposites of sodium polystyrenesulfonate (NaPSS) and ZnO. Its humidity sensing characteristics and the sensing mechanism have been investigated by measuring the complex impedance spectra of the sensor at different humidities. The logarithm of the impedance of sensor based on composite film changes linearly by four-orders of magnitude over almost whole humidity range (11-97% RH). Furthermore, the sensor exhibits a quick response (absorption: 2 s, desorption: 2 s) and small hysteresis (less than 2% RH). The composite film shows better sensing properties than NaPSS film, such as better linearity, quicker response. Explanation to the improvement is attempted by taking into account of the composition and structure of the nanocomposites.     

A NOVEL RESISTIVE HUMIDITY SENSOR BASED ON SODIUM POLYSTYRENESULFONATE/TiO_2 NANOCOMPOSITES

A resistive humidity sensor was prepared based on sodium polystyrenesulfonate (NaPSS)/TiO_2 nanocomposites,and its electrical response to humidity was examined. The sensor exhibits better linearity, smaller hysteresis (<4% RH) andquicker response (absorption: less than 2 s; desorption: less than 20 s) in comparison with sensor composed of NaPSS. Theeffect of concentration of NaPSS and TiO_2 on humidity response of sensors was discussed.     

A resistive-type humidity sensor using composite films prepared from poly(2-acrylamido-2-methylpropane sulfonate) and dispersed organic silicon sol

A composite material of dispersed organic silicon sol and poly(2-acrylamido-2-methylpropane sulfonate) (poly-AMPS) was used to make humidity sensor without protective film or complicated chemical procedures. The organic silicon sol was dispersed well in the poly-AMPS without using dispersion agent. Parameters that may affect the water-resistive but humidity-sensitive characteristic of composite material, the adding amount of organic silicon sol solution and the film of thermal treatment time, were investigated. The microstructure of the material was analyzed, and the humidity sensing and electrical properties of the sensor were measured. The sensor well responded to humidity with a relatively good linearity, though it depended on the applied frequency. The temperature influence between 15 and 35 °C was within −0.17 % relative humidity (RH)/°C in the range of 30–90% RH. The activation energy was maximum around 40% RH. The sensor showed the hysteresis within 5.9%, fast response time, long-term stability (75 days at least) and satisfactory resistance to high humidity atmosphere (97% RH) and chemical environment (20% C₂H₅OH vapor). Analyzing the structure and complex impedance plots of organic silicon sol/poly-AMPS was used to explain improvement in humidity sensing properties in comparison with nano-sized SiO₂ powder/poly-AMPS films.     

Exploring fiber optic approach to sense humid environment over nano-crystalline zinc oxide film

A novel humidity sensor made up of nano-crystalline zinc oxide (ZnO) film, coated onto the U-shaped typical glass substrate as a wave guide, conjugated with an optical fiber and He-Ne un-polarized laser source. The nano-crystalline zinc oxide (ZnO) was synthesized using single molecular precursor method. The resulting material was characterized with Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), thermogravimetric-differential thermal analysis (TG-DTA) and scanning electron microscopy (SEM). In the thin film, ZnO particles exhibited the wurtzite phase structure with the particle size in a diameter range of 70-80 nm. The humidity sensing characteristic has been estimated by measuring the optical permeability (OP) as a function of percentage relative humidity (%RH) in the ranging from 5 to 90 inside a closed chamber. The OP decreases linearly with increase in %RH with a respond time of about 30 and recovery time of 35 s. The sensor exhibits the sensitivity of 0.45 in the %RH range 5-50 and 0.30 from 50 to 90.     

Ultra-thin CoAl layered double hydroxide nanosheets for the construction of highly sensitive and selective QCM humidity sensor

To achieve real-time monitoring of humidity in various applications, we prepared facile and ultra-thin CoAl layered double hydroxide (CoAl LDH) nanosheets to engineer quartz crystal microbalances (QCM). The characteristics of CoAl LDH were investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectric spectroscopy (XPS), Brunauer–Emmett–Telle (BET), atomic force microscopy (AFM) and zeta potential. Due to their large specific surface area and abundant hydroxyl groups, CoAl LDH nanosheets exhibit good humidity sensing performance. In a range of 11.3% and 97.6% relative humidity (RH), the sensor behaved an ultrahigh sensitivity (127.8 Hz/%RH), fast response (9.1 s) and recovery time (3.1 s), low hysteresis (3.1%RH), good linearity (R² = 0.9993), stability and selectivity. Besides, the sensor can recover the initial response frequency after being wetted by deionized water, revealing superior self-recovery ability under high humidity. Based on in-situ Fourier transform infrared spectroscopy (FT-IR), the adsorption mechanism of CoAl LDH toward water molecules was explored. The QCM sensor can distinguish different respiratory states of people and wetting degree of fingers, as well as monitor the humidity in vegetable packaging, suggesting excellent properties and a promising application in humidity sensing.     

Water-resistive humidity sensor prepared by printing process using polyelectrolyte ink derived from new monomer

A simple strategy was developed based on a new monomer containing both photocurable function and ammonium salt, N-(2-cinnamoyloxy)ethyl-N-(2-(methacryloyloxy)ethyl)-N,N-dimethyl ammonium bromide (CMDAB) to obtain photocurable polyelectrolyte ink and stable humidity-sensitive membranes by printing process. Humidity-sensitive membranes are photocrosslinked polyelectrolytes obtained from copolymers of [2-(methacryloyloxy)ethyl] dimethyl propyl ammonium bromide (MEPAB), CMDAB and MMA. A flexible gold electrode/polyimide was pretreated with 2-(mercaptoethyl) cinnamamide (MEC) containing a thiol-coupling agent for the purpose of anchoring the humidity-sensitive polyelectrolyte to the gold electrode. The sensors using screen printing methods reduced the deflection of sensor characteristics showing humidity precision ±1%RH. The photocured copolymer MEPAB/CMDAB/MMA = 63/7/30 show good sensitivity (0.0586 logΩ/%RH) changing resistance approximately four orders of magnitude with relative humidity varying from 20% to 95% and fast response and recovery time. The resultant sensors showed acceptable linearity (Y = -0.04X + 7.0, R(2) = -0.9900) and small hysteresis. The reliability including water resistance and a long-term stability were estimated for the application of the flexible humidity sensor prepared by screen printing process.     

Co-extrusion of multilayer poly(m-xylylene adipimide) nanocomposite films for high oxygen barrier packaging applications

Multilayer packaging films incorporating a montmorillonite layered silicate (MLS)/poly(m-xylylene adipimide) (MXD6) nanocomposite as the oxygen barrier layer and low-density polyethylene (LDPE) as the moisture resistant layer were produced through the co-extrusion process at the laboratory and pilot scale level. Extrusion screw speeds were varied from 30 to 130 rpm in order to produce samples with varying layer thicknesses. The multilayer film structure was scaled up from the laboratory scale to the pilot-level scale based on oxygen transmission data obtained from the laboratory-scale process parameters. Laboratory-scale film results indicated that the film which demonstrated an optimal oxygen transmission rate (OTR) of 0.3 cm³/(m² day) at 60%RH and water vapor transmission rate (WvTR) of 1.4 g/(m² day) at 90%RH had a structure that contained a core barrier film layer of nanocomposite MXD6 that makes up roughly 34% of the total film thickness, with the remainder of the film material consisting of maleic anhydride grafted polyolefin tie layers and LDPE skin layers. The OTR of the films changed as the relative humidity of the test environment was varied from 0 to 90%. However, for the pilot-scale trial it was necessary to reduce the target thickness of the core nylon barrier layer to 22% due to layer-to-layer melt flow instabilities that occurred during processing. The barrier properties of the multi-layer co-extruded films were highly dependant on overall film thickness. The highest performing oxygen barrier pilot-scale film had an OTR of 0.3 cm³/(m² day) (60%RH) and a WvTR of 2.4 g/(m² day) (90%RH) with a core nylon layer of 1.5 mil and a total thickness of 7.7 mil. Correlation of the layer thicknesses to the barrier and mechanical properties of the pilot-scale multilayer films indicated that an increased nanocomposite core layer thickness improved the oxygen barrier performance and decreased film elongation while improving the tear resistance of the films.