PIPD纤维的制备及其结构与性能研究

以2,3,5,6-四氨基吡啶三盐酸盐一水合物(TAP·3HCl·H2O)和2,5-二羟基对苯二甲酸(DHTA)为单体,合成聚[2,5-二羟基-1,4-苯撑吡啶并二咪唑](PIPD),并采用干喷湿纺法制备了PIPD初生纤维,初生纤维在温度400℃,张力33 c N/dtex的条件下进行热处理得到PIPD纤维,研究了PIPD纤维的结构与性能。结果表明:PIPD初生纤维的线密度为959.6 tex,拉伸强度为2.15 GPa,拉伸模量为154.2 GPa;热处理后的PIPD纤维较初生纤维致密程度有所提高,线密度和拉伸强度有所下降,拉伸模量提高,热稳定性较好;纺丝原液脱泡良好、提高纺丝组件的温度均一性以及降低纤维中残酸量可进一步提高PIPD纤维的性能。     

高性能PIPD纤维制备及结构性能研究进展

综述了聚苯撑吡啶并咪唑纤维（PIPD纤维）的制备、结构及其相关性能.研究进展表明,PIPD纤维是20世纪末开发出的一种新型芳香族杂环刚棒聚合物纤维,由于具有特殊的双向氢键网状结构而具有优异的力学性能,尤其是压缩性能明显高于其他同类聚苯并咪唑类高性能纤维,并且耐燃耐热性能和界面粘结性也非常突出,在军事、体育、消防、航空航天等领域将具有广阔的应用前景.     

聚(二羟基苯撑并吡啶双咪唑)的制备及表征

以2,3,5,6-四氨基吡啶(TAP)的盐酸盐和2,5-二羟基对苯二甲酸(DHTA)为原料,进行成盐反应,得到复合盐2,3,5,6-四氨基吡啶-2,5-二羟基对苯二甲酸盐(TD盐),进而聚合得到聚(二羟基苯撑并吡啶双咪唑)(PIPD)。通过核磁共振(NMR)、傅里叶红外(FT-IR)、质谱(MS)、差示扫描量热(DSC)等测试手段对TD盐的结构进行了表征,且通过紫外-可见光(UV-vis)、特性黏度和热失重分析(TGA)等表征方法对由两单体复合盐聚合得到的PIPD聚合物的结构和耐热性能进行了研究。     

两种高性能纤维研究进展

简介了聚对苯撑苯并双恶唑(PBO)纤维和聚二羟基苯撑并吡啶双咪唑(PIPD)纤维的发展历史、制备方法,性能及应用,着重对PBO纤维和PIPD纤维最近几年研究的热点和方向进行了综述.     

PBO纤维毡复合气凝胶高性能材料的制备与性能研究

本文以聚苯撑苯并二噁唑(PBO)纤维毡为增强基材复合SiO2气凝胶制成高性能材料,测试了材料的导热系数、氧指数、强度等指标,并采用扫描电镜对材料的结构和形貌进行了表征.结果表明:该复合材料中SiO2气凝胶以大小不同的颗粒状填充于PBO纤维毡的纤维间空隙中,相较于未复合气凝胶的PBO纤维毡,其导热系数显著降低,并具有较高...     

芳纶复合纳米纤维气凝胶的制备及其性能研究

将SiO2纳米粒子加入到由去质子化方法制备的芳纶纳米纤维分散液中,制备芳纶复合纳米纤维气凝胶.通过一系列表征测试,分析了无机纳米粒子添加的芳纶复合气凝胶的力学性能、热性能和燃烧性能.试验结果表明:制得的复合纳米气凝胶的密度为5.6 mg/cm3,在80％压缩应变下可承受280 kPa的应力,并且具备低导热系数[27.0...     

热塑性聚氨酯中空纤维/SiO2气凝胶隔热材料的制备及性能研究

以热塑性聚氨酯中空纤维为增韧材料,正硅酸乙酯为硅源,采用溶胶-凝胶技术制备了热塑性聚氨酯中空纤维/SiO2气凝胶隔热材料.考察了纤维类型、中空纤维铺设方式、中空纤维规格对SiO2气凝胶隔热性能的影响.结果表明:中空纤维增韧SiO2气凝胶的隔热性能略低于纯SiO2气凝胶,但其韧性有了显著提高.中空纤维垂直铺设,采用合适的内径及壁厚的中空纤维能获得较好隔热性能的SiO2气凝胶隔热材料.     

醋酸纤维素纳米纤维复合气凝胶的制备及性能研究

以醋酸纤维素(CA)为原料,通过静电纺丝制备CA纳米纤维;将CA纳米纤维在去离子水中形成均匀的分散体,然后在分散液中引入N-羟甲基丙烯酰胺(HAM),通过冷冻、热处理制备CA纳米纤维/HAM复合气凝胶(CNFA);探讨了HAM添加量对CNFA力学性能和隔热性能的影响.结果表明:当纺丝液CA质量分数为15％时,静电纺CA...     

超轻耐火SiO2纳米纤维气凝胶的制备及性能研究

以二氧化硅(SiO_2)纳米纤维(SNF)为基体,通过淀粉修饰制备了增韧超轻SiO_2纳米纤维气凝胶(SNFAs)。探讨了SNF与淀粉的质量比对SNFAs的表面形貌、力学性能、隔热性能、热稳定性的影响。结果表明:增韧SNFAs内部的纳米纤维形成互连的三维网络结构;随着淀粉添加比例的增加,SNFAs的压缩强度先增大后减小,密度逐渐增大,导热系数先减小后增大,当SNF与淀粉质量比为1:0.25时,SNFAs压缩强度最大为9.0 kPa,密度为11.5 mg/cm~3,导热系数为0.0258 W/(m·K),比纯SNFAs导热系数低;制备的SNFAs在维持高隔热性能前提下,能够改善SNFAs的力学性能,具有低密度、低导热系数、耐火隔热的特点。     

轻质高强芳纶纳米纤维/聚酰亚胺复合气凝胶的制备及性能

聚酰亚胺 (PI) 因其优异的综合性能备受关注，将其构建成高强度气凝胶对拓展其在航空航天、微电子等高科技领域的应用具有重要意义。本文以4,4’-二氨基二苯醚 (ODA) 和3,3’,4,4’-二苯甲酮四羧酸二酐 (BTDA) 为单体构筑聚酰亚胺气凝胶，通过引入芳纶纳米纤维（ANFs）对气凝胶进行骨架增强，并通过傅立叶红外光谱（FT-IR）、扫描电子显微镜（SEM）等探究了ANFs对气凝胶化学结构、微观形貌以及力学性能等的影响。研究表明，ANFs通过氢键作用与前驱体聚酰胺酸（PAA）结合，并均匀分散在气凝胶骨架中，从而对其进行有效增强。引入ANFs后，气凝胶制备过程中的体积收缩率有效降低，当ANFs添加量增加至PAA的4 wt% 时，气凝胶体积收缩率由63% 降低至54%；与PI气凝胶相比，添加4 wt% ANFs复合气凝胶的杨氏模量由1.8 MPa提升至6.9 MPa，压缩回弹率提升了37%。     

Microstructural evolution of mullite nanofibrous aerogels with different ice crystal growth inhibitors

Mullite nanofibrous aerogels with low density, low thermal conductivity and high service temperature (as high as 1400 °C) was fabricated by the freeze-casting method, and two different kinds of ice crystal growth inhibitors, glycerol as the cryoprotector and agarose as the gel-former, were adopted respectively to influence the growth of ice crystal, thereby adjusting the sample microstructure (including the pore size and the pore distribution). The addition of glycerol could influence the growth of the ice crystal, leading to the pore structure changing from the cellular pores to the spherical pores and the decrease of the large pore size, consequently resulting in the increase of the sample density and compressive strength. The addition of agarose could inhibit the growth of the ice crystal due to the formation of gel network, resulting in the disappearance of the large pores (cellular pores). The sample with high agarose content exhibited a relatively high compressive strength of 252.41 kPa due to high density and uniform pore structure. The research of this work provides an effective method to regulate the properties of nanofibrous aerogel to meet the demand of different applications.     

The role of the hydrogen bonding network for the shear modulus of PIPD

Ab initio total energy calculations at the DFT-GGA level for PIPD are reported. Both the monoclinic crystal with a bi-directional hydrogen-bond network and the triclinic crystal with a sheet-like network are studied. It is concluded that the latter is the more plausible microstructure for the fibre based on the following: (i) After optimisation of the lattice parameters and atomic positions it has a lower energy. (ii) The calculated internal shear modulus agrees better with experiment. (iii) The minimal shear stiffness constant, which is interpreted as the upper limit on the compressive strength, compares favourably with the experimental compressive strength.The hydrogen bonding network plays a crucial—but indirect—role in explaining the high compressive strength. It replaces the weak components of the lateral bonding, such as present in many high performance polymer materials with low compressive strength, e.g. PBO and PBZT, with much stronger hydrogen bonds. This makes that in PIPD the relatively strong π-π interaction has the weakest resistance against shear.     

Ag/AgCl coated polyacrylonitrile nanofiber membranes: Synthesis and photocatalytic properties

A membrane based photocatalyst consisting of Ag/AgCl coated PAN nanofibers was synthesized in large quantities by electrospinning technique combining electroless plating method and subsequent in situ oxidation strategy. Electrospinning was firstly used to fabricate PAN/AgNO₃ composite nanofibers. After reduction, Ag nanoparticles dispersed along the nanofibers act as seeds in the following metal electroless plating step for the growth of continuous Ag shell. Then an in situ oxidation reaction between Ag shells and FeCl₃ solution was carried on to prepare Ag/AgCl coated PAN nanofiber membranes. The as-prepared materials exhibited excellent photocatalytic activity under visible-light, long-term stability, flexibility, as well as easy separation from the liquid. The present work can open a new and effective route for preparing high-performance membrane based photocatalysts for practical application.     

Preparation, characterization, and encapsulation/release studies of a composite nanofiber mat electrospun from an emulsion containing poly(lactic-co-glycolic acid)

The aim of this study was to investigate the preparation, characterization, and encapsulation/release performance of an electrospun composite nanofiber mat. The hypothesis was that the composite nanofiber mat with nano-scaled drug particles impregnated in biocompatible and biodegradable polymer nanofibers can serve as an innovative type of tissue engineering scaffold with desired and controllable drug encapsulation/release properties. To test the hypothesis, the composite nanofiber mat electrospun from an emulsion consisting of poly(lactic-co-glycolic acid) (PLGA) Rhodamine B (a model compound to simulate drugs), sorbitan monooleate (Span-80, a non-ionic emulsifier/surfactant that is presumably non-toxic/safe for cell-growth), chloroform, DMF, and distilled water was prepared and characterized; and the Rhodamine B encapsulation/release profile in phosphate buffered saline (pH = 7.4) was recorded and analyzed. For comparison purposes, two additional nanofiber mats electrospun from (1) a solution containing PLGA and Rhodamine B, and (2) a solution containing PLGA, Rhodamine B, and Span-80 were also prepared and assessed as the control samples. The results indicated that the composite nanofiber mat electrospun from the emulsion had the most desired and controllable Rhodamine B encapsulation/release profile and the excellent morphological sustainability; thus, it could be utilized as both a drug encapsulation/release vehicle and a tissue engineering scaffold.     

Solid-phase combustion synthesis of calcium aluminate with CaAl2O4 nanofiber structures

Calcium aluminate with CaAl₂O₄ (CA) nanofiber structures was fabricated through a facile solid-phase combustion synthesis method with raw materials of CaO₂, CaCO₃, Al, and Al₂O₃ in Ar atomosphere at a pressure of 0.1 MPa. The results indicated that the relative content of CA decreased, but that of Ca₁₂Al₁₄O₃₃ (C₁₂A₇) increased with the increase of r-value from 0 to 0.5 (r is molar substitution coefficient of CaCO₃ for CaO₂). Interestingly, CA nanofibers with tens of micrometers in length and about 200 nm in diameter were observed in the combustion products with r = 0.2, 0.3, 0.4, respectively. The more nanofibers can be found in the products, as the content of CaCO₃ in raw material ratios increased. And the yield of nanofibers in the combustion product with r = 0.4 is the highest. The typical round droplet on head of nanofiber indicated that the growth process of nanofibers was governed by vapor-liquid-solid (VLS) mechanism with base growth mode. It is proposed that both higher reaction temperature and reducing atmosphere are requirements for the growth of CA nanofiber during the process of combustion synthesis. The nanofiber cannot be generated in the samples r0, and r5, because the gaseous Ca is absent due to oxidizing atmosphere and lower reaction temperature, respectively.     

配位插层法制备三聚氰胺-甲醛树脂/Cu2+ -蒙脱石纳米复合材料

采用微波加热溶液交换法分两步将提纯后的天然膨润土转变为Cu2 -膨润土(铜基土),通过三聚氰胺单体与Cu2 -蒙脱石层间Cu2 的配位作用,把三聚氰胺单体引入蒙脱石层间,然后加入甲醛经插层原位聚合制备三聚氰胺-甲醛树脂/Cu2 -蒙脱石纳米复合材料。X-射线衍射结果表明蒙脱石的层间距由1.25 nm增加到1.58 nm,所得产物为三聚氰胺-甲醛树脂/Cu2 -蒙脱石插层型纳米复合材料。     

PAN/MWNTs纳米纤维薄膜的制备和性能

采用浓硝酸和浓硫酸混合溶液将多壁碳纳米管(MWNTs)进行功能化处理,与聚丙烯腈(PAN)共混,通过静电纺丝制备了PAN/MWNTs纳米纤维薄膜。分析了MWNTs的结构和分散性及PAN/MWNTs纳米纤维的性能。结果表明,经过混酸处理后,MWNTs表面产生了羧基官能团,可以长时间稳定均匀分散在N,N′-二甲基乙酰胺(DMF)溶液中。混酸处理后的MWNTs在PAN基体中均匀分散,减少了静电纺丝过程中珠滴地形成。添加MWNTs后,PAN纳米纤维的强度提高,含MWNTs质量分数5%的PAN纳米纤维的拉伸强度提高了35.48%。     

Enhanced magnetic and dielectric properties of Y doped bismuth ferrite nanofiber

Yttrium doped Bismuth ferrite (BFO) nanofiber was fabricated via a sol-gel-based electrospinning process with the fiber diameter in the range of 60–220 nm. The crystal structure, magnetic and dielectric properties were investigated at room temperature. The Rietveld refinement results indicate the phase transition from space group R3c to Pbnm by the Y doping. Dramatic increase of magnetization has been achieved in Y doped BFO nanofiber. Compared with BFO nanoparticle, the Bi_0.95Y_0.05FeO₃ nanofiber exhibits nearly eighteen-fold improved magnetization, which is the strongest in the reported Y doped BFO at the same doping level. The largely improved magnetization mainly originates from the serious suppression of spiral spin structure by the small crystal size of nanofiber structure. Moreover, the Bi_0.95Y_0.05FeO₃ nanofiber holds the lower dielectric loss and obvious dependence of the capacitance on bias voltage, indicating the improved ferroelectricity due to the decreased leakage current. The simultaneous enhancement of ferroelectricity and magnetization in Y doped BFO nanofiber suggests that nanofiber structure plays an important role in improving multiferroic performance.