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。     

三元共聚聚酰亚胺纤维的制备

针对均苯四甲酸二酐和4,4′-二氨基二苯醚体系两步法制备的聚酰亚胺(PI)纤维强度比较偏低的问题,加入刚性单体对苯二胺,在N-甲基吡咯烷酮中进行三元共聚得到聚酰胺酸(PAA),选用水和乙醇的混合溶液为凝固浴通过干湿法纺制出PAA纤维。对PAA纤维进行不同倍数的拉伸,然后通过优化酰亚胺化条件制得了致密的PI纤维,处理温度在400℃时,其强度和模量可分别达到4．29 cN/dtex和389 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。     

静电纺聚酰亚胺非织造布的制备与表征

以N,N-二甲基乙酰胺(DMAc)为溶剂,3,3',4,4'-二苯醚四甲酸二酐(ODPA)和4,4'-二氨基二苯醚(ODA)为单体,利用高压静电纺丝技术,制备了聚酰胺酸(PAA)和聚酰亚胺(PI)非织造布,并采用扫描电镜(SEM)对PAA及PI非织造布的表面形态进行表征,研究了PI非织造布的力学性能。结果表明:经300℃热亚胺化处理得到的PI非织造布,纤维平均直径减小到500nm以下,纤维的带状形貌与PAA明显不同,并且出现了收缩、弯曲等现象。静电纺丝法制得的PI非织造布的力学性能仍然比较优越。     

系列聚酰亚胺的制备及其结构表征

以二苯醚四羧酸二酐（0DPA）为二酐单体,对苯二胺（PDA）和二胺基二苯基醚（ODA）为二胺单体,通过低温缩聚合成一系列聚酰胺酸（PAA）和聚酰亚胺（PI）薄膜,对其结构和力学性能进行表征,并比较ODPA—PDA和ODPA—ODA薄膜的力学性能。结果表明,PAA的酰亚胺化较完全;链节元素组成与空间构型对于PAA与PI薄膜的力学性能影响较大,其中,PI（ODPA—PDA）薄膜的拉伸强度达到450MPa。     

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。     

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。     

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。     

高压静电纺丝法制备聚酰亚胺超细纤维无纺布膜

采用制备聚合物纳米纤维的一种简易的重要基本方法,即静电纺丝技术,以实验室合成的聚酰胺酸（PAA）溶液为纺丝溶液,采用自制静电纺丝机进行电纺得到PAA纤维无纺布膜。采用傅立叶变换红外光谱分析技术对无纺布膜的化学结构进行了表征分析;由PAA及聚酰亚胺（PI）无纺布膜的谱图吸收峰对比分析得知,纤维热酰亚胺化的程度是比较完全的;但由相应吸收峰对比分析得知,热酰亚胺化的程度并没有达到100％。     

共聚聚酰亚胺纤维的结构与性能

将均苯四甲酸二酐（PMDA）／4,4＇-二苯醚二胺（ODA）／2-对氨基苯基-5-氨基苯并咪唑（PABZ）共聚体系的聚酰胺酸（PAA）溶液进行湿法纺丝,制成PAA纤维,采用热亚胺化的方法制得聚酰亚胺（PI）纤维。研究了不同的纺丝及其后处理条件对PI纤维结构性能的影响。结果表明：当聚合物中PABZ含量较高时,PAA初生纤维拉伸比较高,热亚胺化温度高,PI纤维的力学性能显著提高。当PABZ／ODA摩尔比为7／3,PAA初生纤维拉伸比为2．48,热处理温度512℃,处理时间5rain时,PJ纤维力学性能最好,其拉伸强度和初始模量分别为10．2,322cN／dtex,PI纤维热性能较好,在510℃左右仍有较好的热稳定性,其玻璃化转变温度为410～433℃。扫描电镜观察和广角X射线衍射分析表明,较高的热亚胺化温度会导致PI纤维内部出现裂纹,结晶度较低为16．63％。     

聚酰胺酸纤维热酰亚胺化的研究

采用聚酰胺酸纤维热酰亚胺化处理方法制备聚酰亚胺纤维,研究了不同热处理条件对聚酰亚胺纤维性能的影响。结果表明,采用定长处理和持续升温方式,真空氛围,热处理温度420℃,得到的聚酰亚胺纤维性能较好,其断裂强度达5.06 cN/dtex。     

纳米芳纶增强聚酰亚胺气凝胶纤维的制备及其性能研究

以3,3′,4,4′-联苯四甲酸二酐和1,4-二氨基苯二胺共聚制备聚酰胺酸盐前驱体溶液,通过湿法纺丝,然后经过超临界二氧化碳干燥和热亚胺化处理制得纳米芳纶(ANFs)增强聚酰亚胺(PI)气凝胶纤维(简称PI/ANFs气凝胶纤维),研究了气凝胶纤维的结构与性能。结果表明:傅里叶变换红外光谱和X射线衍射光谱表征所制备的PI/ANFs气凝胶纤维为目标产物;PI/ANFs气凝胶纤维的截面具有大量的孔结构且分布较为均匀;PI/ANFs气凝胶纤维的比表面积为152 m²/g,孔径主要分布在10~25 nm之间,密度为0.21 g/cm³,孔隙率大于85%;PI/ANFs气凝胶纤维在空气气氛下的最大热分解温度为625℃,在氮气气氛下950℃的残炭率为67%;PI/ANFs气凝胶纤维的断裂强度和初始模量分别为(2.5±0.5)MPa和(109±10)MPa。     

Effect of chemical structure and preparation process on the aggregation structure and properties of polyimide film

In this article, polyimide (PI) films were fabricated via the three‐step method including the reactions of condensation polymerization, chemical imidization, and thermal imidization. In comparison with the conventional two‐step method to produce PI films, there was an additional step in the present method, i.e., chemical imidization. The aim of chemical imidization was to get PI intermediates with different pre‐imidization degree (pre‐ID). And PI component in PI intermediates acted as in‐situ rigid‐rod segments and induced orientation in the films of PI intermediates. Then the orientations of molecular chains were preserved in the following thermal imidization, and caused the difference in aggregation structure and property of the final PI films. The test results indicated that the orderly degree of molecular chains and mechanical properties of PI films increased with pre‐ID increasing. Furthermore, this tendency was much more obvious for more rigid backbone structure. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

亚胺化对聚酰亚胺热学性能的影响

用均苯四甲酸二酐(PMDA)与4,4’-二氨基二苯醚(ODA)为单体,聚合得到一定表观黏度的聚酰胺酸(PAA)。通过调节温度和时间两个变量,并采用红外光谱仪、高温综合热分析试着分别对PAA凝胶膜热亚胺化过程以及热学稳定性进行了研究,结果表明:亚胺化程度随时间的增加而增大,亚胺化程度随着亚胺化温度的提高同样增大;通过热重分析仪对聚酰亚胺薄膜热学性能进行了研究,随着薄膜亚胺化程度的增大,薄膜的热稳定性提高。     

Effect of thermal history during drying and curing process on the chain orientation of rod-shaped polyimide

Chain orientation in polyimide (PI) film is influenced by the thermal history during drying and curing process. The amount of residual solvent and the degree of imidization, among other factors, play a major role in determining the chain orientation during the process. In the present study, poly(amic acid), the precursor of PI, coated on the glass substrate was imidized to PI through different drying and curing protocols. On the way of complete imidization, the residual solvent concentration and the degree of imidization were characterized using confocal Raman spectroscopy. The poly(amic acid) began to imidize quickly while retaining more solvent in the film as the initial drying temperature increased. The degree of in-plane chain orientation in fully imidized PI film made by different process protocols was compared using polarized Raman spectroscopy. The fully imidized PI showed the lowest degree of in-plane chain orientation when it was processed by the protocol with the highest drying temperature. The difference in the degree of in-plane chain orientation among different PI films significantly influenced the in-plane thermal expansion coefficient, while no significant change in crystallinity or glass transition temperature was observed.     

Influences of different imidization conditions on polyimide fiber properties and structure

In the present work we prepared co-polyimide (PI) fibers with excellent mechanical and dielectric properties by the wet-spinning method. The co-PI fiber exhibited high mechanical property with a tensile strength of 2.61 GPa and modulus of 86.7 Gpa as well as a low dielectric constant and a dielectric loss factor of 2.7463 and 0.00793 at 10 GHz, respectively. The relationship between the properties and the microstructure of co-PI fibers after heat-drawing was investigated. The results revealed that the hydrogen-bond associations and the microvoids structure were highly affected by imidization conditions. Both the formations of the hydrogen-bond associations and the evolution of microvoids were attributed to the change in tensile strength. Furthermore, the fibers prepared at proper conditions possessed fewer surface defects as well as homogeneous inner structure. Our work demonstrates the structure–property relationship in annealed PI fibers, which may provides a new avenue to access high-performance PI fibers.     

Polyimide fibers prepared by a dry‐spinning process: Enhanced mechanical properties of fibers containing biphenyl units

Polyimide (PI) fibers with enhanced mechanical properties and high thermal and dimensional stability were prepared via a two‐step dry‐spinning process through the introduction of 3,3′,4,4′‐biphenyl tetracarboxylic dianhydride (BPDA) containing biphenyl units into rigid homopolyimide of pyromellitic dianhydride (PMDA) and 4,4′‐oxydianiline. The attenuated total reflectance–Fourier transform infrared spectra results imply that the incorporated BPDA moieties accelerate the imidization process and increase the imidization degree (ID) of the precursor fibers; this was attributed to the increased molecular mobility of the polymer chains. Two‐dimensional wide‐angle X‐ray diffraction spectra indicated that the prepared PI fibers possessed a well‐defined crystal structure and polymer chains in the crystalline region were highly oriented along the fiber axis. The PI fiber, with the molar ratio of PMDA/BPDA being 7/3, showed optimum tensile strength and modulus values of 8.55 and 73.21 cN/dtex, respectively; these were attributed to the high IDs and molecular weights. Meanwhile, the PI fibers showed better dimensional stability than the commercial P84 fiber, and this is beneficial for its security applications. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43727.