聚酰亚胺改性酚醛泡沫

介绍了聚酰亚胺(PI)与酚醛树脂的共混改性方法,同时探讨了聚乙二醇(PEG)的加入对酚醛/聚酰亚胺复合体系的性能影响.结果显示经聚酰亚胺改性后,酚醛复合材料形成了网络互穿结构,其热稳定性、压缩强度以及隔热性能均有明显提高,粉化率、吸水率也有所降低,但仍然具有较高的脆性.在酚醛/聚酰亚胺复合体系中适当的加入聚乙二醇后,材料的脆性得到改善,然而其它性能如压缩强度、热稳定性和隔热性却比加入前有所降低.通过研究发现,为了改善酚醛泡沫塑料总体性能,聚酰亚胺和聚乙二醇的最佳用量均为3%～5%.     

热释电研究聚碳酸酯掺杂染料体系的玻璃化转变

采用热刺激电流 /松弛谱图分析法 (TSC/RMA)研究了聚碳酸酯掺杂染料体系 (TDAA/PC)的玻璃化转变 ,发现染料含量增加 ,体系的玻璃化转变温度 (Tg)随之降低 ,玻璃化转变的温度范围变宽 .在TDAA掺杂质量比达到 4wt%时 ,其玻璃化转变 (协同松弛 )延伸至 95℃ ,温度范围增加到 3 5℃ .在较大的温度范围内存在协同松弛 ,说明在低于Tg 数十度的温度时 ,染料发色体的极化松弛仍然主要受聚合物玻璃化转变的控制 .     

高耐热、低介电常数含氟聚酰亚胺材料的合成与性能研究

合成了一系列新型含氟耐高温、低介电常数聚酰亚胺 (PI)材料 ,并对其进行了热性能、电性能等方面的测试 .结果表明 ,这类分子结构中含吡啶环单元的材料可保持PI固有的耐热性能 ,其在氮气下的热分解温度为 5 4 5～ 6 0 1℃ ;而侧链的双三氟甲基取代结构一方面使分子具有较高的氟含量 ,另一方面增大了分子的自由体积 ,这两方面的共同作用使得这类材料具有优良的介电性能 ,其介电常数为 2 86～ 2 91;击穿电压为15 0 4～ 197 3kV mm .     

空心玻璃微珠复合聚酰亚胺泡沫的泡孔结构与性能

通过填充空心玻璃微珠,采用预聚法制备了空心玻璃微珠复合聚酰亚胺泡沫,研究了空心玻璃微珠填充量对复合聚酰亚胺泡沫的泡孔结构、热性能和压缩性能的影响规律。结果表明,随着空心玻璃微珠填充量的增加,聚酰亚胺泡沫泡孔结构变得精细,并且热稳定性、玻璃化转变温度和压缩性能都随之提高。当填充量(空心玻璃微珠与均苯四甲酸酐的质量比)达到20%时,泡沫5%热失重温度提高了13.9℃,玻璃化转变温度提高了8.1℃,压缩强度提高了约21%,压缩模量提高了约12%。     

基于乙炔基-苯并噁嗪单元双重交联反应的聚酰亚胺树脂的制备与性能

为开发可低温固化的聚酰亚胺树脂, 通过分子结构设计将苯并噁嗪单元引入聚酰亚胺树脂中, 合成了含苯并噁嗪单元及乙炔基封端的双官能化新型聚酰亚胺预聚体(PIBzA). 经高温处理, 苯并噁嗪单元发生开环交联, 同时, 乙炔基端基发生三聚成环反应, 从而在固化树脂中形成双重交联网络结构. 苯并噁嗪单元的引入使聚酰亚胺树脂最快固化反应温度降低约32 ℃, 有效降低了固化温度. 同时, 苯并噁嗪单元的引入未大幅度降低树脂的耐热稳定性, 其玻璃化转变温度(T_g)介于266~290 ℃之间, 5%热失重温度(T_d,5%)接近500 ℃, 依然可以满足耐高温复合材料的应用需求. 此外, PIBzA固化树脂具有低介电特性, 其介电常数k介于2.3~3.0, 介电损耗介于0.002~0.008, 可满足透波复合材料及先进微电子封装材料的应用需求.     

高性能聚酰亚胺热塑性树脂的工业化进展

介绍了40多年来国内外开发的高性能热塑性聚酰亚胺(Ployimide,简称PI)树脂的主要品种,如Vespel,Torlon,Ultem,Aurum等。如何使得这类材料同时具有优异的综合性能和熔融加工性是人们的研究焦点。本文还介绍了GE公司新近报道的新品种Extem和最近引起国内外同行关注的异构聚酰亚胺树脂。异构的聚酰亚胺是近几年新兴起的结构材料之一,与传统结构的聚酰亚胺比较,具有更高的玻璃化温度,良好的溶解性能,低的熔融粘度,宽的加工窗口,和相当的机械性能和热稳定性,是一种较有发展前景的结构材料。     

可溶性聚酰亚胺的制备及其在液晶显示器上的潜在应用

以3,5-二硝基苯甲酰氯和4-羟基联苯为原料,合成了功能性二胺单体3,5-二氨基苯甲酸联苯酯(DABBE).用此单体与3,3′-二甲基-4,4′-二氨基二苯甲烷(DMMDA)、3,3′,4,4′-二苯醚四甲酸二酐(ODPA)共缩聚,采用低温缩聚-化学亚胺化的方法,通过调节共聚物组成制备了5种聚酰亚胺(PI).利用FT-IR、NMR、UV-Vis与DSC等手段对合成二胺单体及聚酰亚胺进行了结构表征和性能测试;研究了其溶解性能、透光性能、取向性能和耐热性能.结果表明,5种聚酰亚胺均可溶于NMP、DMF等极性溶剂;对液晶分子取向时的预倾角随DABBE的比例增加而增大,可达1.8°.但当DABBE的比例增加时,PI的分子量降低,将影响其成膜性能.此外,实验所得的PI透过率大于80%,玻璃化转变温度在220℃以上.     

聚吡咯/多壁碳纳米管及其聚氨酯导电复合材料的制备和性能

以羧基化多壁碳纳米管(MWCNTs)做模版剂,采用化学氧化法将吡咯(Py)在羧基化MWCNTs表面聚合制备PPy/MWCNTs导电材料,将其添加到溶剂型聚氨酯(PU)溶液中制备了PPy/MWCNTs/PU导电复合材料,研究了Py用量对PPy/MWCNTs及其PU复合材料性能的影响.研究表明,随Py用量的增加,PPy/MWCNTs的长度不变,管径增大,sp~2和sp~3杂化C含量先提高后减少,N的掺杂梯度降低,PPy/MWCNTs的导电率高于羧基化MWCNTs和PPy.当Py用量为羧基化MWCNTs的20%时,其导电率最大.PPy/MWCNTs中N元素的掺杂程度及其管径变化是引起PPy/MWCNTs/PU复合材料的性能不同的主要原因.增加Py用量,MWCNTs中亲水的羧基因对PPy掺杂而消耗,相同导电材料用量时纳米导电粒子数目相对减少,PPy/MWCNTs/PU复合材料的耐水性能提高,定向应力、储能模量和玻璃化温度降低,导电率先增加后减小.当Py用量为羧基化MWCNTs的15%时,导电率最大.     

含叔丁基/异丁基二胺的可溶性透明聚酰亚胺的合成与性能

通过分子设计合成了异丁基桥联2-叔丁基苯胺的新型二胺单体4,4′-(2-异丁基)双(2-叔丁基苯胺), 并将其分别与4种商品化芳香族二酐经高温“一步法”缩聚制得了系列聚酰亚胺(PI)树脂. 采用多种测试手段研究PI的结构和性能, 结果表明, 该系列新型聚酰亚胺不但可溶于N-甲基吡咯烷酮及N,N-二甲基甲酰胺等高沸点溶剂, 而且在乙酸乙酯和三氯甲烷等低沸点溶剂中也具有良好的溶解性. 该系列PI保持了良好的热稳定性, 在N₂中5%热失重温度均在480 ℃以上, 玻璃化转变温度(T_g)介于307~356 ℃之间. 经溶液刮涂制得的PI薄膜具有良好的光学透明性, 在可见光区平均透过率可达82.3%~89.1%, 截止波长介于313~363 nm之间. 同时, 该系列PI薄膜还具有良好的机械性能和疏水性, 有望应用于光伏发电及柔性显示等领域.     

聚酰亚胺纳米杂化材料的制备、结构和性能

介绍了聚酰亚胺（PI）纳米杂化材料的四种制备方法：溶胶－凝胶法、插层法、分散法、相转移分散聚合法。纳米粒子在PI材料中分散性良好。由于纳米粒子本身 性和纳米粒子改变了PI材料的应力作用点，随着SiO2,AIN等纳米粒子含量增加，PI杂化的玻璃化温度、热分解湿度、拉伸强度、断裂伸长率、杨式模量、密度增加，线性膨胀系数减少。对介电性能的影响因不同纳米材料而异。     

Friction and wear behavior of PI and PTFE composites for ultrasonic motors

High‐performance polymer‐based frictional materials have become increasingly important to improve the mechanical output properties of ultrasonic motors. This study discussed the friction and wear behavior of 2 dominating frictional materials of polymer composites for ultrasonic motors, polyimide (PI), and polytetrafluoroethylene (PTFE) filled by aramid fibers (AF) and molybdenum disulfide (MoS₂). To explore the wear mechanisms, the tribo‐pair contact stress was theoretically characterized, and the interface temperature rise was numerically predicted. The predictions showed that the flash temperature on asperity tips could reach the glass transition temperature of the polymer materials. The experimental results indicated that the contact stress and sliding speed have a small effect on the friction of the PI composite but influence considerably the friction of the PTFE composite. A higher contact stress brings about a higher specific wear rate, but a higher sliding speed reduces the wear rate. Compared with AF/MoS₂/PTFE, the AF/MoS₂/PI has much better tribological performance under high loads and speeds.     

聚酰亚胺无机纳米杂化材料

聚酰亚胺(PI)作为一种功能材料，具有良好的介电性、优良力学性能，已被广泛应用于航空航天及微电子领域，但其明显的吸水性和热膨胀性限制了其在高温和精密状态下的应用。无机纳米材料具有很低的热膨胀系数和较低的吸水性，非常适合于对PI的改性。本文阐述了PI纳米杂化材料的制备方法。概要介绍了PI纳米杂化材料的类型、特点、性能及应用领域，并对这类材料的发展前景进行了综述。     

Scalable Reaction-spinning of Rigid-rod Upilex-S(R) Type Polyimide Fiber with an Ultrahigh Tg

In the family of polyimide (PI) materials,Upilex-S(R) film has been a shining star through the research PI materials due to its appealing merits.Unfortunately,the wholly rigid-rod backbone and easily formed skin-core micromorphology and microvoids of Upilex-S～ type PI lead to the high difficulty in melt-and wet-spinning fabrication.Herein,we propose a facile and scalable method,reaction-spinning,to fabricate the Upilex-S(R) type PI fiber,in which the rapid solidification of spinning dope and partial imidization take place simultaneously.Thus,the stability and mechanical strength of as-spun fibers can be improved,and the microvoids in fibers can be greatly reduced in relative to the wet-spun fibers.The resultant Upilex-S(r) type PI fiber shows higher tensile strength and modulus than most commercial thermal-oxidative polymeric fibers with an ultrahigh glass transition temperature Tg of 478 ℃.Moreover,the WAXS and SAXS results indicate that orthorhombic crystals are formed for Upilex-S(r) type PI fiber in the post hot-drawing process.Increasing the hot-drawing temperature results in a continuous crystallization and high orientation of PI chains in amorphous phase and perfects the existing lamellar structure,which make a great contribution to the improved mechanical property.     

Preparation and characterization of polyimide/pure silica zeolite hybrid films

In this study, amino derivative of pure silica zeolite nanocrystal (A‐PSZN) was dispersed into polyimide (PI) matrix to prepare PI/A‐PSZN hybrid films, and their thermal and mechanical properties, as well as hydrophobicity, were characterized scientifically. The test results show that PI/A‐PSZN hybrid films possess higher glass transition temperature, higher thermal stability and lower in‐plane coefficient of thermal expansion than pristine PI. The mechanical property data suggest that the incorporation of A‐PSZN results in an increase in Young's modulus and tensile strength of the hybrid films, but as its content exceeds the critical value (maybe 5 wt%), its enhancement effect on the hybrid's strength and toughness gets weaker. Furthermore, liquid dripping imaging analysis results indicate that the film's hydrophobicity is clearly improved by the introduction of A‐PSZN. As compared with PSZN, A‐PSZN exhibits better effect on enhancing the overall performance of pristine PI films. A comparison with other studies suggests that PI/A‐PSZN is a hybrid film with superior comprehensive properties. Copyright © 2013 John Wiley & Sons, Ltd.     

引入不对称结构对聚酰亚胺模塑料加工性能的改善

采用联苯四酸二酐（BPDA）与4,4′-二胺基二苯醚(4,4′-ODA)和3,4′-二胺基二苯醚(3,4′-ODA)聚合后,经亚胺化,制备了一系列二胺不同配比的高强度易加工的聚酰亚胺模塑料。 并对其流变性能、力学性能及热学性能进行测试。 结果表明,随着3,4′-ODA含量的增加模塑料的冲击强度没有大的改变,而流变性能随3,4′-ODA含量的增加而提高,w(3,4′-ODA)在50%时,玻璃化转变温度为275 ℃,材料的冲击强度为141 kJ/m2。 模压压力为20 MPa时加工性能优异。     

Honeycomb‐Patterned Polyimide Film as a Versatile Coating for High‐Performance Dielectric Material

A honeycomb‐patterned porous film was conveniently prepared by means of the microemulsion method and then used as an effective coating for improving the dielectric properties and water resistance of polyimide (PI) film while maintaining its mechanical properties. The dielectric properties could be regulated by tuning the structure of the porous film through controlling its formation conditions. When suitable conditions were used, the prepared composite PI film exhibited a significant reduction of 28.3 % in its dielectric constant and 9.48–54.99 % in dielectric loss accompanied by an extremely low water uptake of 0.62 % relative to the 2.47 % of flat PI film. The composite PI film also displayed excellent durability under moist conditions, as the dielectric constant was still below 2.4 after exposure to 75 % relative humidity for more than 12 h. This provides a novel method to improve and control the dielectric properties of materials. It also suggests that this film is a suitable candidate for coating dielectric materials in high‐humidity environments.     

Synthesis and Characterization of a Novel High-Temperature Structural Adhesive Based on MDA-BAPP-BTDA Co-Polyimide

A series of polyimide(PI) adhesives were synthesized from 2,2'-Bis [4-(4-aminophenoxy)phenyl] propane(BAPP), 4,4'-Diaminodiphenylmethane (MDA) and 3,3',4,4'-Benzophenonetetracarboxylic acid dianhydride (BTDA) via a two-step process. PI adhesives with different BAPP content were characterized in regard to their structure, thermal stability, mechanical properties and adhesive performance. Results showed that these PIs had excellent thermal stability, whose glass transition temperature (Tg) were around 300°C. While, superior dynamic mechanical behavior was observed, and the maximum loss factor declined with the increase of BAPP content. Single-lap shear strength of over 15.58 MPa at room temperature was obtained, and it remained high even at the temperature of 350°C. Factors that could affect bonding strength of these PI adhesives such as molar ratio of the diamine monomers, surface roughness of adherends and curing processes were investigated.     

Microstructure and properties of organosoluble polyimide/silica hybrid films

Organosoluble polyimide/silica hybrid materials were prepared via the sol-gel process and their pervaporation properties were studied. The organosoluble polyimide (PI) was based on 4,4′-oxydiphthlic dianhydride (ODPA) and 4,4′-diamino-3,3′-dimethyldiphenylmethane (DMMDA). The surface chemical structure of polyimide/silica films was analyzed by Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) and the results show that the completely hydrolysis of alkoxy groups of precursors and formation of the three-dimensional Si-O-Si network in the hybrid films. The morphology and the silica domain thus obtained were studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM), respectively. The silica particle size in the hybrid is in the range of 40-100 nm for the hybrid films when the amount of silica is less than 20 wt%. The strength and the modulus of the hybrid films are improved and the mechanical properties were found to be strongly dependent on the density of the crosslink. The glass transition temperature (T_g) of the hybrid films was determined by dynamic mechanical analysis (DMA) and the value increased 15-20 °C as the silica content increased. Furthermore, the pervaporation performances of the prepared hybrid films were also investigated for the ethanol/water mixtures at different temperature.     

Preparation of Meldrum's acid-functionalized polyimides exhibiting organo-soluble,reactive, self-crosslinkable,and colorless features

Functional polyimides (PIs) having some desired properties, for example, organo-solubility, chemical reactivity, crosslinkable feature, and high transparency in visible region, are attractive for specific applications. This work reports an effort to integrate the above-mentioned properties in one polyimide through introduction of Meldrum's acid (MA) moieties to polyimide chains with using a MA-containing diamine (MADA) as a monomer. The polyimide prepared with MADA and 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) (PI[MADA-6FDA]) has a number-averaged molecular weight of 56,800 g mol⁻¹, shows good solubility in tetrahydrofuran and aprotic high polar solvents, and exhibits post-reactivity/crosslinkability through MA-mediated ketene chemistry. Crosslinked PI(MADA-6FDA) film shows a glass transition temperature of 289°C, a dielectric constant of about 2.78, and high flexibility bearing a near-180° bending. The MA-mediated ketene chemistry contributes to in situ building up covalent linkages between PI chains and silica nanoparticles (SNPs) in preparation of PI/SNPs nanocomposite films (NCF). Formation of the PI/SNPs NCFs enhances the thermal and mechanical properties, reduces the dielectric constants, and increases the transparency. The properties of the MA-functionalized PI are attractive for further studies on their applications.     

Molecular aggregation of solid aromatic polymers. II. Mechanical properties of aromatic polyimide film

Molecular aggregation of the aromatic polyimide poly(4,4′-oxydiphenylene-pyromellitimide) is influenced by the initial imidization temperature and by cold drawing. The effect of molecular aggregation in polyimides on their mechanical properties has been investigated. The density of a polyimide in which molecular aggregation gives an amorphous state is increased slightly by cold drawing. On the other hand, if molecular aggregation leads to a heterogeneous two-phase structure, the density is decreased by cold drawing. With increasing initial imidization temperature, the α absorption peak in dynamic tensile measurements becomes broader and smaller, and shifts to a higher temperature. From analysis of correlations between molecular aggregation and mechanical properties, it is concluded that the mode of molecular motion corresponding to the α dispersion in polyimide is a long-range cooperative motion of the main chain which is associated with the glass transition.