干法纺聚酰亚胺纤维的结构与性能

以均苯四甲酸二酐、4,4'-二氨基二苯醚、3,3'-二氨基二苯醚为原料,以N,N-二甲基乙酰胺为溶剂,制得聚酰胺酸(PAA)纺丝液,采取干法纺丝制得PAA初生纤维,将PAA初生纤维经过300~380℃的热处理后,得到聚酰亚胺(PI)初生纤维,在400℃下对PI初生纤维进行热拉伸,最终得到PI纤维,研究了热处理温度、热拉伸倍数等对PI纤维的结构与性能的影响,比较了PI纤维与P84纤维和芳纶1313的性能。结果表明:在300~380℃的热处理温度下,随着温度升高,PI纤维的力学性能降低,最佳热处理温度为300℃时制得的PI初生纤维于400℃下进行热拉伸3.0倍,所得PI纤维的断裂强度为5.8 c N/dtex,初始模量为69.4c N/dtex,其力学性能优于P84纤维及芳纶1313;PI纤维在空气中失重5%和10%的温度分别为560,570℃,其起始分解温度高于P84纤维和芳纶1313,热性能更好;PI纤维经高温热拉伸,纤维内部分子链沿纤维轴向高度取向,表现出典型的取向诱导结晶效应。     

聚酰亚胺薄膜及纤维的探索研究

利用均苯四甲酸二酐(PMDA)、4,4'-二氨基二苯醚(4,4'-ODA)和自制三单体在强极性非质子有机溶剂N,N-二甲基乙酰胺(DMAc)中进行共缩聚反应,制得高粘度的聚酰胺酸(PAA)溶液,经涂膜、热亚胺化,得到坚韧透明的聚酰亚胺(PI)薄膜,其具有较好的拉伸断裂强度和合适的伸长率;同时将得到的PAA溶液进行湿法纺丝,制成PAA纤维,采用热亚胺化和高温拉伸的方法制得PI纤维,其断裂强度能达到3.67cN/dtex。     

聚酰胺酸酰亚胺化条件及其对聚酰亚胺力学性能的影响

采用均苯四酸二酐(PMDA)和4,4'-二氨基二苯醚(ODA)为单体,N-甲基吡咯烷酮(NMP)为溶剂,合成了黏度为1.87 dL/g的聚酰胺酸(PAA)。对聚酰胺酸分别进行了热酰亚胺化和化学酰亚胺化处理,研究了完全酰亚胺化所需的条件以及不同酰亚胺化方式对聚酰亚胺(PI)纤维条断裂强度的影响;对PAA初生纤维条进行拉伸和酰亚胺化处理的顺序不同,所得到的聚酰亚胺(PI)纤维条的力学性能不同,采用先酰亚胺化再拉伸的方法能得到力学性能更优异的聚酰亚胺(PI)纤维条。     

热处理过程中聚酰亚胺纤维结构与性能的演变

以联苯二酐与2,5-二(4-氨基苯基)嘧啶、4,4-二氨基二苯醚进行共聚,制备高相对分子质量的聚酰胺酸(PAA)纺丝原液,采用湿法纺丝、热环化、热拉伸制备共聚聚酰亚胺(PI)纤维,研究了热处理过程中PI纤维结构与性能的演变过程。结果表明:当热环化温度高于300℃时,PAA基本环化形成PI结构;在热拉伸作用下,PI纤维的凝聚态结构更加规整,且随拉伸倍数的提高,纤维的晶区取向度增加,同时伴随着力学性能的提升;当热拉伸倍数为2.00时,所得PI纤维的力学性能最佳,其拉伸强度及拉伸模量分别可达到21.8 cN/dtex和642.7 cN/dtex。     

含砜基聚酰亚胺的合成及其中空纤维膜的制备（英文）

以4,4'-(六氟异丙烯)二酞酸酐(6FDA)与4,4'-双(4-氨基苯氧基)二苯砜(BAPS)为反应单体,以N-甲基-2-吡咯烷酮(NMP)为溶剂,合成了聚酰胺酸(PAA),将PAA溶液采用流延成膜的方法制备成薄膜;另外,将PAA溶液采用干-湿法纺丝工艺制得PAA中空纤维膜,再将PAA薄膜及其中空纤维膜在300℃左右的高温热环化制得6FDA-BAPS型聚酰亚胺(PI)膜。研究了6FDABAPS型PI及其中空纤维膜的结构与性能。结果表明:所合成的6FDA-BAPS型PI为目标产物,其在NNP、N,N-二甲基乙酰胺、四氢呋喃中具有良好的溶解性能。6FDABAPS型PI中空纤维膜外皮层致密、支撑层疏松多孔,该中空纤维膜具有较高的热学性能和力学性能,在氮气氛围中热失重5%的温度为511℃,断裂强度为26.5 MPa。     

共聚聚酰亚胺纤维的制备及其性能研究

采用4,4’-二氨基二苯醚和1,6-己二胺(HDA)为二胺单体,与均苯四甲酸酐(PMDA)在二甲基乙酰胺(DMAc)中共聚得到聚酰胺酸(PAA)纺丝原液,通过干法纺丝工艺路线纺制PAA初生纤维,利用热酰亚胺化制备了共聚型聚酰亚胺(PI)纤维;通过红外光谱分析、动态力学分析、热重分析、X射线衍射等手段分析了PI纤维的力学性能及热性能。结果表明:红外光谱分析发现HDA的长亚甲基链引入到PI的链中;当HDA质量分数为20%时,PI纤维的断裂强度和模量分别为5.1 cN/dtex和76 cN/dtex;动态力学和热重分析发现,纤维的玻璃化转变温度为315～380℃,热稳定性在400℃以上;纤维经热处理后聚集态结构存在一定的有序性。     

聚酰胺酸的合成及其酰亚胺化研究

采用均苯四酸二酐(PMDA)和4,4'-二氨基二苯醚(ODA)为单体,N,N-二甲基乙酰胺(DMAc)为溶剂,合成聚酰亚胺的前驱体聚酰胺酸(PAA)。研究了溶剂体系、反应温度、时间、投料比和总固含量等因素对所得聚酰胺酸特性黏度的影响。试制了聚酰胺酸和聚酰亚胺(PI)薄膜,对其进行了红外光谱分析及力学性能测试。     

PPD对PAA溶液性质及其纤维结构的影响

以均苯四酸二酐(PMDA)和4,4,-二氨基二苯醚(ODA)以及PMDA,ODA和对苯二胺(PPD)共聚合成聚酰胺酸(PAA),经湿法纺丝制备PAA纤维.研究了PPD的引入对PAA原液性质及其纤维形态结构的影响.结果表明:PAA的特性粘数随着PPD含量增加而提高;PPD的引入使PAA的凝固性能及其纤维力学性能提高;凝固浴为水/乙醇,水含量较高时,含有PPD的PAA纤维截面结构变得疏松多孔;凝固浴为水/N甲基吡咯烷酮,水体积分数为70%～80%时,得到致密无孔的改性PAA纤维.     

聚酰亚胺纤维的制备及其结构研究

将均苯四甲酸二酐(PMDA)和4,4’-二氨基二苯醚(ODA)在N-甲基吡咯烷酮(NMP)中进行溶液聚合得到聚酰胺酸(PAA)溶液,并用该溶液进行干湿法纺丝得到PAA纤维,分别用化学酰亚胺化法和热酰亚胺化法得到聚酰亚胺(PI)纤维。研究了凝固浴组成和工艺条件对PAA形态结构和纤维性能的影响,以及不同酰亚胺化方法对PI纤维形态结构和性能的影响。结果表明:以甲醇为凝固浴制备的PAA初生纤维,无孔致密,最高拉伸强度和初始模量分别为2．21 cN/dtex和40．73 cN/dtex;采用化学酰亚胺化法制得的PI纤维中存在少许孔洞缺陷,其强度较低,热酰亚胺化法制得的PI纤维无孔致密,其强度和模量分别达到2．83 cN/ dtex和43．4 cN/dtex。     

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。     

Kinetics of imidization of poly(amic acid) in miscible and immiscible polymer blends

Blends of commercial poly(amic acid), LARC-PAA polymer were prepared with thermoplastic polyimide P84. The blends were shown to be miscible over a certain composition range. Chemical imidization of LARC-PAA in the blends leads to phase separation. Thermal imidization of LARC PAA in the blends was carried out in the solid state. Miscible compositions of the blend remained miscible after imidization and showed a single glass transition for each blend. Immiscible compositions after imidization remained immiscible and showed two glass transition temperatures in the DSC scans. The kinetics of thermal imidization of PAA to polyimide (PI) in the solid state were studied using FTIR. In the immiscible blend the kinetics remained unaffected while in the miscible state the rate of imidization became faster than that of the pure PAA.     

Fabrication and properties of anisotropic polyimide aerogels with aligned tube-like pore structure

Polyimide (PI) aerogels with highly aligned tube-like pores were fabricated by unidirectional ice crystal-induced self-assembly method. During this process, the mold bottom contacted with the freezing medium, the aqueous solution of poly(amic acid) (PAA) ammonium salt in the mold was unidirectionally frozen, the ice crystals grew from the bottom to top of PAA ammonium salt (PAS) solution along the freezing direction, which endowed PI aerogels with aligned tube-like pores after sublimation of ice crystals and thermal imidization of PAS. The obtained aerogels had low densities (0.077–0.222 g cm⁻³) and high porosities (83.8–94.2%) and exhibited anisotropic morphology and properties. Their compression strength in vertical direction (parallel to freezing direction) was higher than that in horizontal direction (perpendicular to freezing direction). Their heat transport in horizontal direction was much slower than that in vertical direction; the aerogels had better thermal insulating property in horizontal direction. This facile approach contributed to prepare new type of PI aerogel materials. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48769.     

Study on morphology control and how to affect mechanical properties of polyimide/silica hybrid films

A series of polyimide (PI)/silica hybrid films were prepared by sol–gel method, using hydrolyzed tetraethoxysilane and poly amic acid‐imides (PAA‐Is), which were different imidization degree controlled by chemical imidization method. The imidization degree was characterized by Fourier transform infrared spectra and their corresponding morphology was characterized by scanning electron microscopy. The results show that there are two kinds of silica particles and their formative morphology obeys the double phase separation mechanism. According to the increase of PAA‐I imidization degree, amount of nano silica particles decreased and the diameter of macro silica particles increased in the hybrid films. Tensile testing, dynamic mechanical analysis, and thermal mechanical analysis results show that, according to the amount of nano silica particles increasing, the hybrids have the higher the mechanical properties, glass transition temperature (T_g), and thermal expansion coefficient. Through controlling PI/silica hybrid films microstructure, its mechanical properties can be controlled. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Processable conductive blends of polyaniline/polyimide

By using camphorsulfonic acid (CSA) to protonate polyaniline (PANI), the counterion enabled the PANI–CSA complex processable as a solution phase. So camphorsulfonic acid (CSA)-doped polyaniline/polyimide (PANI/PI) blend films were prepared by the solvent casting method using N-methylpyrrolidinone (NMP) as a cosolvent followed by thermal imidization. The conductivity of the PANI–CSA/PAA (50 wt % PANI content) is greater than that of the pure PANI sample at room temperature. As the thermal imidization proceeded, molecular order of polymer chain structure was improved in the resulting PANI–CSA/PI film due to the annealing effect of PANI chain, and this PANI–CSA/PI film showed higher conductivity than PANI–CSA and PANI–CSA/PAA film. PANI–CSA/PI blend films had a good thermal stability of conductivity at high temperature. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1863–1870, 1998     

Preparation and properties of core–shell silver/polyimide nanocomposites

A new series of core–shell structured silver/polyimide (PI) nanocomposites was prepared by in situ polymerization followed by the chemical imidization of poly(amic acid) (PAA, precursor of PI) at a low temperature. The TEM images showed that the silver cores of the nanocomposites were encapsulated with homogeneous shells with thickness of 4 and 8 nm at silver contents of 90 and 60 %, respectively. The shell thickness was controlled by varying the content of PAA. FTIR spectroscopic analysis indicated that the imide ring formation occurred after the chemical imidization. The Ag/PI nanocomposites showed excellent thermal stability and exhibited only 10 % weight loss at 300 °C in the air. Moreover, percolation was observed at silver weight fractions close to the critical value, and the maximum dielectric permittivity of the nanocomposites was 120, which is about 40 times higher than that of pristine PI.     

The retarding effects and structural evolution of a bio-based high-performance polyimide during thermal imidization

The thermal imidization evolution of a bio-based high-performance polyimide, namely adenine-containing polyimide (API), was investigated by thermogravimetric analysis (TGA), in situ Fourier transform infrared spectroscopy (in situ FTIR), and wide-angle X-ray diffraction (WAXD), in contrast to an adenine-free 4,4′-oxydiphthalic anhydride (ODPA)/4,4′-oxydianiline (ODA) PI. The influence derived from adenine was focused. At precursor stage of API (polyamic acid, PAA), the H-bonding interaction of PAA–PAA type as well as the especial interaction between the secondary amine of adenine and solvent (dimethylacetamide, DMAc) was discovered. Structural evolution of API was traced by in situ FTIR and multistage WAXD from PAA stage to PI stage. Compared with OPI, the retarding effects were found in the process of thermal imidization of API, partly due to the formation of H-bonding derived from the extra secondary amine of adenine moieties, which complicated the H-bonding form in API. Finally, a hypothesis of evolution of thermal imidization process about API molecule was proposed in contrast with adenine-free ODPA ODA PI. Compared with the consistency of both API and ODPA ODA PI in PAA stage, API possessed a more delicate thermal imidization process. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46953.     

Properties of gradient polyimide aerogels prepared through layer-by-layer assembly

A series of density gradient polyimide (PI) aerogels were prepared using layer-by-layer assembly and radial freezing method. Briefly, a layer of poly(amic acid) (PAA) ammonium salt aqueous solution was first radially frozen. Then, the second layer of PAA ammonium salt (PAS) aqueous solution of different concentration was added on the top of the first PAS layer and radially frozen. A multilayer gradient PAS solid sample could therefore be fabricated by repeating this similar procedure. The density gradient PI aerogels were obtained after freezing drying and final thermal imidization treatment. Each layer of gradient PI aerogels had anisotropic pore structure, which consisted of tube-like pores along the radial direction and toward the center axis of the cylindrical samples. The compressive strength of five-layer gradient PI aerogel was higher than that of three-layer gradient and single-layer PI aerogels with the same density. The gradient PI aerogels exhibited anisotropic heat transfer behavior in the direction of density gradient, and heat transfer from the higher density side to the lower density side was faster.     

Effects of water on the preparation,morphology, and properties of polyimide/silica nanocomposite films prepared by sol–gel process

Polyimide/silica (PI/SiO₂) nanocomposite films with 10 wt % of silica content were prepared by sol–gel process under the conditions with and without additional water. The presence of additional water has great effect on the silica particle size and thus on the properties of the prepared PI/SiO₂ films. The results indicated that with additional water, the silica particles formed before the imidization of poly(amic acid) (PAA) and aggregated with the increasing of temperature and degree of the proceeding imidization process. For the nonaqueous process, the hydrolysis condensation reaction of tetraethoxysilane (TEOS) did not occur until the imidization of PAA took place, and no silica particles were found in the unimidized PAA films. The hydrolysis–condensation reaction of TEOS was initiated simultaneously by the trace water released from the imidization reaction, the self‐catalysis mechanism of the approach provide a means of achieving uniformly dispersed silica particles formed in the PI matrix with particle size in the range of 30–70 nm. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1579–1586, 2007