基于“静电纺丝——热压”技术制备高性能多孔锂电隔膜

为制备基于“静电纺丝-热压”聚酰亚胺(PI)纳米纤维膜,将m(BPDA-ODA型聚酰胺酸(PAA))∶m(PMDA-ODA型聚酰胺酸(PAA))以质量比1∶1混合制备共混溶液,采用高压静电纺丝技术制备PAA无纺布,再通过热压在高温下亚胺化获得PI纳米纤维膜,研究热压温度对共混聚酰亚胺薄膜性能及静电纺丝纳米纤维形貌结构的影响。通过傅里叶红外光谱仪(PTIR)、扫描电镜(SEM)、万能拉伸试验机、动态热机械分析仪(DMA)对纳米纤维膜进行测试与表征。结果表明:同一批次PAA无纺布,平板硫化仪150℃,3 MPa压力处理5 min得到的PI纳米纤维膜具有较均匀的直径、良好的形貌以及较好的力学性能。     

玉米蛋白纳米纤维的制备及其交联研究

用静电纺丝技术制备了玉米醇溶蛋白(Zein)纳米纤维膜,对所制备的纤维膜进行了扫描电镜(SEM)、X射线衍射(XRD)、远红外(FTIR)表征。SEM结果表明:质量分数为30%的Zein溶液所制备的纳米纤维形貌最佳。XRD结果显示静电纺丝未改变Zein的晶相。FTIR结果表明:电纺并未改变Zein的主要结构。对Zein纳米纤维膜进行了紫外线交联和戊二醛交联,并对交联后的纤维膜进行了比表面积和拉伸性能测试。结果表明:交联后Zein纳米纤维膜的力学性能有显著提高,但戊二醛交联引起了比表面积的急剧减小,会对纤维膜的通透性造成较大影响;而紫外线交联的纳米纤维膜的力学性能不仅得到了提高,微观结构也不受影响。     

聚乙烯醇纳米纤维膜的制备

采用静电纺丝方法制备了聚乙烯醇(PVA)纳米纤维,探讨了工艺参数对纳米纤维形貌的影响,并对PVA纳米纤维膜进行热处理,研究了热处理时间与温度对纳米纤维膜力学性能的影响。研究表明:PVA质量分数在6%~10%区间内变化时,可得到直径分布较为均匀的纳米纤维;在其它条件相同时,随纺丝电压的升高,PVA纳米纤维的不匀增大;接收距离的改变对PVA纳米纤维的直径变化影响不大;随PVA质量分数的增加,纳米纤维膜的断裂强度和断裂伸长率逐渐增大;在热处理时间相同时,PVA纳米纤维膜的断裂强度随温度的升高而增大;处理温度相同时,随处理时间的延长,PVA纳米纤维膜的断裂强度变化不大。     

BTCA改性PEG/PVA相变储能纤维的结构与性能

将聚乙二醇(PEG)与聚乙烯醇(PVA)溶液混合,加入丁烷四羧酸(BTCA)作为交联剂配制纺丝原液,采用干法纺丝制得BTCA改性PEG/PVA相变储能纤维;研究了BTCA含量、热处理条件对交联程度的影响,并对纤维的结构、形态、储能性能及力学性能进行了分析。结果表明:在热处理温度为180℃,热处理时间为12 min时,纤维可达到良好的交联效果,纤维的交联程度随BTCA含量的增加呈上升趋势,BTCA质量分数为3%时达到平衡;改性纤维中PEG以独立微相区形式存在,而经热处理后可保留在交联网络中;热处理后的改性纤维力学性能随BTCA含量增加而提高,储能性能也增加且稳定;当BTCA质量分数为6%时,热处理后的纤维断裂强度达3.49 cN/dtex,再经沸水处理后纤维相变焓值可达23.01 J/g,PEG保留率达80%。     

聚合物含量对膜蒸馏用聚偏氟乙烯电纺纳米纤维膜的影响

为考察聚合物含量对聚偏氟乙烯(PVDF)静电纺丝纳米纤维膜的结构和性能的影响,在二甲基甲酰胺与丙酮质量比为9:1的条件下,制备了无纺布支撑的PVDF静电纺丝纳米纤维膜,进行了聚合物PVDF含量对纺丝液基本性质与膜的形貌结构及分离性能的影响分析。结果表明,提高纺丝液中PVDF含量,纺丝液的表面张力与电导率降低,纳米纤维间珠粒数量减少,纤维直径增大。直接接触式膜蒸馏脱盐应用实验表明,PVDF的质量分数为12%条件下制备的疏水膜,在盐溶液与冷侧循环水温度分别为80℃与20℃时,其通量可达62.38 kg/(m~2·h),产水电导率为8μS/cm,盐截留率达到99.99%以上。     

静电纺丝法制备聚酰亚胺/碳化硅复合纳米纤维

利用聚酰胺酸(PAA)溶液和纳米碳化硅(SiC)混合物作为纺丝液,通过静电纺丝法制备聚酰胺酸/碳化硅(PAA/SiC)复合纳米纤维,PAA/SiC复合纳米纤维亚胺化后得到聚酰亚胺/碳化硅(PI/SiC)复合纳米纤维。研究了PAA溶液中PAA含量、纺丝电压、纺丝距离及SiC含量对PAA/SiC复合纳米纤维形貌的影响,利用热重法分析了PI/SiC复合纳米纤维的热稳定性。结果表明,使用固含量为15%的PAA溶液作为基体材料,再将纳米SiC以6%的含量均匀分散于基体材料中制备出纺丝液,在纺丝电压为10～18kV左右、纺丝距离为15cm时,可制备出直径250nm左右、光滑、连续、SiC分布均匀的PAA/SiC复合纳米纤维。PI/SiC复合纳米纤维热稳定性优异,氮气气氛中热分解温度为550℃。     

静电纺聚氨酯纳米纤维膜的制备及其性能研究

静电纺丝技术是制备纳米纤维膜的一种比较简单而且常用的技术。对静电纺丝技术制备聚氨酯(TPU)纳米纤维膜的最佳纺丝条件进行探索。此外,对制备的TPU纳米纤维膜进行了力学性能和介电性能的表征。结果表明,在纺丝液质量分数为12%、电压20 V、接收距离15 cm、THF与DMF的体积比为5∶1的条件下,制备的TPU纳米纤维膜表面无珠粒、纤维直径均匀,纺丝效果最佳。与纯TPU薄膜进行性能对比,TPU纳米纤维膜的断裂伸长率和拉伸强度远低于纯TPU薄膜,前者的介电常数比后者略低,但是前者的弹性模量低于后者。制备的TPU纳米纤维膜可以应用于气体过滤领域。     

静电纺醋酸纳米纤维滤膜的制备及性能分析

为了制备高效低阻的纳米纤维空气过滤膜,采用静电纺丝技术,制备了醋酸(CA)不同质量分数、不同纺丝时间的CA纳米纤维膜,研究了CA质量分数和纺丝时间对CA纳米纤维膜的微观形貌、透气性、过滤性能等性能的影响。结果发现:随着CA质量分数和纺丝时间的增加,CA纳米纤维膜的透气率先减小后增加,过滤效率和阻力压降均先升高后降低,当CA的质量分数为12%,纺丝时间为60 min时,透气率达到247.67 mm/s,水接触角104°,过滤效率为99.94%,阻力压降为238.14 Pa,此时品质因子达到最大数值为0.030 95 Pa~(-1)。     

静电纺丝制备甚低介电常数聚酰亚胺/纯硅沸石复合纤维膜

采用静电纺丝技术制备聚酰亚胺(PI)纤维膜,并通过考察纺丝条件对PI纤维形貌的影响确定制备PI纤维膜的合适条件。在此基础上,将3-氨丙基三乙氧基硅烷表面改性纯硅沸石纳米晶(A-PSZN)引入聚酰胺酸(PAA),通过静电纺丝及热酰亚胺化处理制备PI/A-PSZN复合纤维膜,并对纤维膜的介电常数和力学性能进行详细研究。研究结果表明制备形貌规整的PI纤维的合适条件为:PAA溶液固含量为15%(wt),外加电压为15 k V,接收距离为15 cm;在1 MHz测试频率下PI纤维膜的介电常数为1.61,尽管添加A-PSZN并未对纤维膜的介电常数带来明显影响,但是有利于提高纤维膜的力学性能,PI/7%(wt)A-PSZN杂化纤维膜的杨氏模量和拉伸强度分别由基体的0.15 GPa和29.4 MPa提高至0.584 GPa和41.3 MPa。     

聚乙烯醇/壳聚糖复合电纺纤维膜的制备及表征

利用静电纺丝法制备了聚乙烯醇PVA/壳聚糖CS纳米纤维复合膜,并采用戊二醛蒸气对其交联处理。通过扫描电子显微镜(SEM)观察探讨了不同质量配比、助纺剂的添加以及电纺环境条件对复合纤维膜纤维直径及表面形貌的影响。通过傅里叶变换红外光谱(FTIR)对PVA/CS复合纳米纤维膜做了特征官能团分析,并对其热力学性能及其耐水性进行了表征。结果表明滴加7%(V/V)二甲基亚砜、0.5%(V/V)丙三醇、0.5%(V/V)吐温80的3%(V/V)的乙酸为溶剂,PVA和CS质量配比为90/10,环境湿度0±15%电纺条件下制备的复合纤维形态均一,无珠串无液滴;FTIR研究显示,复合纤维的两种组分发生一定的相互作用,成功制备了戊二醛交联PVA/CS纳米纤维膜;热重(TG)、差热(DSC)结果都进一步说明CS和PVA之间形成氢键,戊二醛交联后复合纤维的热稳定性进一步增强。交联前后纤维膜的耐水性结果表明交联后的共混纤维膜有良好的抗溶解性,在水中可以很好的保持纤维的结构。     

响应面优化法在PDMS/PVDF膜制膜条件优化中的应用

用响应面优化法优化了乙烯基封端PDMS/PVDF渗透汽化透醇膜的制膜条件,研究了硅橡胶浓度、B/A质量比、交联温度和交联时间对膜性能的影响,拟合了分离因子、渗透通量与四因素之间的回归方程,并用方差分析法考察了四因素的主效应、二次效应以及相互作用效应对复合膜的分离因子与渗透通量的影响。研究发现,硅橡胶浓度对膜的分离因子与渗透通量的影响最为显著,交联时间对分离因子几乎没有影响。通过对回归方程的优化分析得知,在料液乙醇浓度为10%(wt),操作温度40℃条件下,当硅橡胶浓度为93%(wt),B/A质量比为0.08,交联温度为100℃,交联时间为13.83 h时,膜的综合分离性能达到最佳,此时分离因子与渗透通量预测值分别为9.47、77.57 g(m2 h)1,渗透侧乙醇浓度达到51.3%(wt)。回归方程的验证实验结果表明,回归方程的估计值与实验值较为吻合,可用于乙烯基封端的PDMS/PVDF复合膜的渗透汽化性能的预测与优化。     

低熔点PET-PTMG共聚醚酯的合成与表征

将对苯二甲酸二甲酯(DMT)、间苯二甲酸二甲酯(DMI)、乙二醇(EG)、新戊二醇(NPG)进行酯交换反应后,再与聚四氢呋喃醚(PTMG)进行缩聚反应,制得低熔点共聚醚酯。采用傅里叶变换红外光谱(FT-IR)、核磁共振氢谱(1H-NMR)、差示扫描量热分析(DSC)、动态热力学分析(DMA)对共聚醚酯的结构与性能进行了表征。结果表明:在其他条件相同时,随NPG比例的增加,共聚醚酯的粘度增大,其NPG与EG链段比值提高,玻璃化转变温度(Tg)升高。当nDMT:nDMI为1:1,nNPG:nEG为3.3:6.7,PTMG质量分数为31.9%时,制得的共聚醚酯的Tg为25.79℃,熔点约130℃;35℃时,共聚醚酯贮能模量最大,耐热性能较好。     

Electrospun crosslinked poly(acrylic acid) fiber constructs: towards a synthetic model of the cortical layer of nerve

In an attempt to mimic properties of the polyanionic nanofibrous cortical layer (ectoplasm) of nerve, tube‐shaped poly(acrylic acid) (PAA) nanofiber constructs were prepared via electrospinning. The influence of processing parameters on the morphology of the electrospun PAA nanofibers was systematically investigated. Smooth and uniform PAA nanofibers with average fiber diameter of 820 nm were produced at a concentration of 4 wt% with a flow rate of 0.8 mL h^?1 when a high voltage of 15 kV was applied. Water‐stable PAA nanofibers were obtained by thermally crosslinking PAA with ethylene glycol. The resulting tubes were neutralized to the sodium polyacrylate form and were shown to undergo reversible and abrupt length changes upon titration with CaCl₂ followed by titration with sodium citrate. The sharpness of the length transition was found to be highly dependent upon the bathing NaCl concentration and the operation temperature. It is suggested that electrospun PAA may be a promising candidate as a key element of an abiotic macromolecular mimic of selected properties of axons. © 2014 Society of Chemical Industry     

Study of nanofiber scaffolds of PAA,PAA/CS,and PAA/ALG for its potential use in biotechnological applications

In recent times, electrospun nanofibers have been widely studied from several biotechnological approaches; in this work, poly(acrylic acid) (PAA) solutions mixed with chitosan and alginate were electrospun and characterized to determine the behavior of these fibers when used in combination with bacteria, different samples were incubated with the bacterial strains: Streptomyces spp., Micromonospora spp., and Escherichia coli and a OD600 test was performed. The formation of nanofibers via electrospinning and the physicochemical properties of the obtained fibers were evaluated. Results showed that the presence of chitosan enhanced the thermal stability of PAA, since PAA/alginate fibers lost 5% of their mass at 41°C, whereas PAA/chitosan lost this amount at around 125°C. The fibers demonstrated suitable characteristics to be used as a bacteria bioreactor.     

聚乳酸基纳米纤维素/石墨烯导电复合膜的制备与表征

利用真空抽滤方法,制备了纳米纤维素/石墨烯导电膜,将其嵌在聚乳酸表面得到聚乳酸基纳米纤维素/石墨烯导电复合膜。傅里叶红外（FT-IR）表征结果表明石墨烯与纳米纤维素之间存在一定的相互作用;当纳米纤维素与石墨烯质量比为1：2时,导电复合膜的电导率为12 S·cm^-1,抗张强度达到13.62 MPa,水接触角为80.6°。热重分析（TGA）表征结果表明导电复合膜有良好的热稳定性,300℃时不同质量比的导电复合膜的失重量低于10%,相比纳米纤维素,在相同温度下失重量减少了20%。以聚乳酸材料为基体的导电复合膜,其抗张强度比未被嵌聚乳酸基体的纳米纤维素/石墨烯导电膜提高15～23倍,将聚乳酸基纳米纤维素/石墨烯导电复合膜埋在土壤中5周后,质量损失了3.7%。聚乳酸材料优异的力学性能和可降解性,扩展了纳米纤维素/石墨烯导电复合膜的应用范围。制备的导电复合膜在柔性导电材料领域有潜在的应用前景。     

Thermal analysis and its application in evaluation of fluorinated polyimide membranes for gas separation

Seven polyimides based on (4,4′-hexafluoroisopropylidene) diphthalic anhydride, 6FDA, with different chemical structures were synthesized in a single pot two-step procedure by first producing a high molecular weight polyamic acid (PAA), followed by reaction with acetic anhydride to produce polyimide (PI). The resulting polymers were characterized using thermal analysis techniques including TGA, derivative weight analysis, TGA–MS, and DSC. The decarboxylation-induced thermal cross-linking, ester cross-linking through a diol, and ion-exchange reactions of selected polyimide membranes were investigated. Cross-linking of polymer membranes was confirmed by solubility tests and CO₂ permeability measurements. The thermal analysis provides simple and timesaving opportunities to characterize the polymer properties, the ability to optimize polymer cross-linking conditions, and to monitor polymer functionalization to develop high performance polymeric membranes for gas separations.     

Sorption of malachite green on vinyl-modified mesoporous poly(acrylic acid)/SiO2 composite nanofiber membranes

Vinyl-modified mesoporous poly(acrylic acid)/SiO₂ (PAA/SiO₂) composite nanofiber membranes were prepared through a sol-gel electrospinning process. The sorption behavior of malachite green on the membranes was studied. Fourier transform infrared (FTIR) results demonstrated that vinyl groups were grafted onto the silica skeleton. Transmission electron microscopy (TEM) images confirmed the formation of mesopores on the electrospun nanofibers and the pore size was 3.8 nm based on the Barrett-Joyner-Halenda (BJH) model. According to Brunauer-Emmett-Teller (BET) method, the specific surface area of the membranes was 523.84 m²/g. Three widely used isotherms, the Freundlich, Langmuir, and Redlich-Peterson isotherms, were used to model the experimental data of malachite green adsorption on PAA/SiO₂ nanofiber membranes. The best fit was found to be Redlich-Peterson isotherm and the equilibrium adsorption capacity was 220.49 mg/g. The adsorption kinetics followed a pseudo-second-order model. The removal of malachite green from the aqueous phase reached 98.8% in 240 min. The membranes can be regenerated by treated with alcohol solution and reused for multiple cycles, which is beneficial for practical application.     

Natural rubber/poly(acrylic acid) semi‐interpenetrating polymer network membranes for the pervaporation of water–ethanol mixtures

Pervaporation membranes for the dehydration of water–ethanol mixtures were prepared from a semi‐interpenetrating polymer network (semi‐IPN) of natural rubber (NR) and crosslinked poly(acrylic acid) (PAA). The swelling studies revealed that hydrophilic PAA present in the semi‐IPN membranes caused the membranes to swell greatly in water. The swelling degree of the membranes in water was significantly affected by the amount ratio between the hydrophobic NR and the hydrophilic PAA. The sorption experiments of the NR/PAA membranes in various concentrations of water–ethanol mixtures suggested the preferential sorption to water. However, for the membrane with high PAA content, the water sorption selectivity decreased considerably at high water concentration of water–ethanol mixtures because the membrane was in the highly swollen state. Pervaporation separations of water–ethanol mixtures using NR/PAA membranes were performed and it was found that at low water concentrations of feed mixtures, increasing the PAA content of the membrane can enhance both water permeation flux and selectivity. Additionally, under low feed water concentration, increasing the feed temperature would increase the water flux with the decreasing of the ethanol flux. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Nanofiltration membranes prepared by interfacial polymerization on thin-film nanofibrous composite scaffold

Nanofiltration (NF) membranes, consisting of a composite barrier layer prepared by interfacial polymerization of polyamide around the ultra-fine cellulose nanofibers (CN) layer in a thin-film nanofibrous composite (TFNC) scaffold, were demonstrated. Two interfacial polymerization pathways (termed IP and IP-R), regarding the arrangement of the aqueous and organic phases, were investigated. It was found that interfacial polymerization with the aqueous phase above the organic phase (IP-R) yielded better filtration performance, i.e., IP-R based membranes exhibited a higher MgCl₂ rejection than IP based membranes. Transmission electron microscopy (TEM) observation indicated that the denser part of the barrier layer was on the CN layer surface of IP-R based membranes, whereas this portion was deeply immersed in the CN layer of IP based membranes. To investigate the structure and property relationship of the composite barrier layer, both IP and IP-R based membranes were treated with 1% trimesoyl chloride (TMC) in hexane. After treatment, the rejection of NaCl was found to increase from 74% to 91% for IP-R based membranes, while remained unchanged (∼75%) for IP based membranes. This behavior can be explained by the decrease in pore size due to the cross-linking of TMC and secondary amino groups in the barrier layer of IP-R based membranes, while the permeability in IP based membranes was probably mainly controlled by the water passage through channels formed at the interface between CN and polymer matrix in the barrier layer of IP based membranes, which is not dependent of the cross-linking reaction.     

The effect of MWNTs concentration and nanofiber orientation on mechanical properties of PAA nanocomposite nanofibrous web

In this research, nanocomposite nanofibrous webs of poly(acrylic acid) (PAA)/multi‐walled carbon nanotubes (MWNTs) were obtained via electrospinning. The effect of MWNTs concentration on the morphology and mechanical properties of PAA/MWNTs nanofibers was investigated by changing the MWNTs content from 0 to 5 wt%. The results showed that average diameter of nanofibers increased with increasing the MWNTs concentration and presence of MWNTs led to the enhancement of mechanical properties. Also, the results revealed that the strength, modulus, and elongation at break of samples increased 3.22, 2.70, and 4.27 fold, respectively, after adding 3 wt% of MWNTs. In addition, the effect of rotating speed of collector on the orientation of PAA nanofibers and its effect on mechanical properties was investigated. Scanning electron microscopy (SEM) studies demonstrated that the degree of nanofibers orientation increased with the augmentation of drum speed to 25 rps. Moreover, the average nanofibers diameter decreased with the increase of drum speed. Improvement of nanofiber orientation resulted in superior mechanical properties that is, higher strength and modulus of aligned nanofiber layers were obtained in comparison to nonaligned layers (12.6 and 26.6 fold, respectively). POLYM. COMPOS., 37:3149–3159, 2016. © 2015 Society of Plastics Engineers