高性能PIPD纤维的研究进展

聚[2,5-二羟基-1,4-苯撑吡啶并二咪唑](PIPD)纤维是荷兰阿克苏·诺贝尔研究所研制成功的一种新型刚棒状聚合物纤维。PIPD纤维具有优异的力学性能、耐热及阻燃性能。大分子链上大量的极性基团形成了独特的二维氢键网络结构,使纤维的压缩强度为目前所有有机聚合物纤维之首。PIPD纤维优异的黏接性能使其在复合材料领域具有广阔的应用前景。对PIPD纤维的单体合成、聚合物制备、纺丝工艺、纤维的结构与性能以及应用等进行了介绍和讨论。     

添加不同物质的聚乙烯醇/海藻酸钠静电纺丝研究

分别添加少量NaCl、乙酸、表面活性剂十二烷基硫酸钠(SDS),研究少量添加物对海藻酸钠/聚乙烯醇(PVA)溶液性质和静电纺纤维的影响,并初步探讨了溶液静电纺丝机制。结果表明:NaCl改变了溶液的电导率和黏度,乙酸降低了溶液的黏度、提高了溶剂挥发性,SDS降低了溶液的表面张力;适量的添加物可使纤维形貌得到改善;添加物对电纺纤维化学结构无本质影响;无机盐离子加剧了纤维拉伸作用,结晶性有所提高;处于泰勒锥处液滴表面受到静电排斥力、表面张力、同种聚合物分子间的氢键作用力、不同聚合物分子间的氢键作用力以及聚合物同水等溶剂形成的氢键作用力。     

中国科学家首次研制出尼龙固态电解质

正尼龙是一种具有80多年历史的经典聚合物。其独特的酰胺键(肽键)使其具有很高的弹性,丰富的氢键网络结构也使其具有一定的机械强度。尼龙在生活中最为人所知的应用当属被年轻女性所钟爱的尼龙丝袜。近日,尼龙固态电解质在中国科学院青岛生物能源与过程研究所首次研制成功。4月2日,该所崔光磊研究员团队的这项研究成果在线发表于《先进功能材料》。"这项工作简单来说,就是重新设计了传统经典聚合物尼龙6的结构,使其具有离子传导性。"崔光磊表示,他们用高浓度的锂盐水溶液,破坏了尼龙6中的丰富的氢键网络,并使其再生为以阴阳离子缔合形式桥接的交联结构。     

疏水缔合水溶性耐温耐盐聚合物的研究进展（二）

(接上期 )3　聚合物溶液性质的影响因素疏水缔合水溶性耐温耐盐聚合物分子链含有许多带电基团和疏水基团 ,分子内电性斥力作用及极性基团的水化作用使大分子链呈疏松伸展状态 ,当聚合物达到一定临界浓度时 ,分子间的疏水缔合作用、氢键及库仑作用使大分子链交联形成具有一定强度的空间网架结构 ,使该类聚合物在临界浓度以上具有很大的流体力学体积 ,因此具有很强的增粘能力。这种能力与聚合物分子量、聚合物中离子基团、疏水基团的类型、链长及含量、聚合物分子链上疏水基团序列分布、无机盐、剪切作用、温度和表面活性剂等因素密切相关。此…     

聚酰胺纤维

20003077聚酞胺化学与物理性质综述WilsonM·P.W·;37届奥地利杜宾国际化纤会议:研究与开发的最新成果,p.507一534(98.9.16一18)(英),ITT Cat.No.TS1548.5.1554 1998 pt.2在尼龙聚合物分子中,重复的酞胺基千CO一NH于存在于烃链之中,该基团可在链间或与其他如水和产生强烈正电的分子形成氢键。本文讨论了化学结构和氢键密度,对尼龙纤维的性质以及对各种商业化应用的相关性质的影响。氢键赋予的低程度的分子间键合,可使纤维在弯曲和加捻时的原纤化减少,结果导致了尼龙的优良耐磨性。这些氢键还使纺织品、地毯及产业用织物获得了满意的…     

纤维对地聚合物抗压强度的影响研究

为提高粉煤灰基地聚合物抗压强度,以纤维作为增韧材料,重点考察了纤维种类和掺量对地聚合物强度的影响.木质素纤维、聚酯纤维和玻璃纤维的最佳掺比分别为0.3%、0.1%和0.3%.过量木质素纤维导致地聚合物局部强度降低,过量玻璃纤维使得地聚合物孔隙增加,导致强度降低.掺加玻璃纤维的粉煤灰基地聚合物抗压强度高(33.25 MPa),其微观结构分析表明Si-O-Si和Si-O-Al聚合度较高.     

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.     

静电纺丝技术在固体氧化物燃料电池中的应用

采用静电纺丝技术制备的纳米纤维材料具有长度可控,结构有序的特点,用该纳米纤维制备的固体氧化物燃料电池(SOFC)电极具有独特的结构优势,可以有效提升SOFC的性能。纳米纤维电极具有更大的比表面积、孔隙率和活性位点,有利于气体的吸附、解离,更有利于离子和电子沿着纤维方向快速传导,从而更有效地促进氧还原反应的进行。静电纺丝技术与溶液浸渍技术相结合,可以构筑结构可控的纳米纤维复合电极,该类电极具有优异的催化性能,有效地提升了SOFC在中低温下的性能。未来需要深入研究聚合物及外部环境对纳米纤维强度的影响,进一步提升纳米纤维的强度,优化电极结构。     

沥青及聚丙烯纤维增韧粉煤灰-矿渣基地质聚合物的制备

本文采用双掺沥青和聚丙烯纤维对碱激发粉煤灰-矿渣基地质聚合物进行了强化增韧研究.结果表明当沥青及聚丙烯纤维掺量分别为1wt％和0.6wt％时,地质聚合物28 d龄期表现出9.7 MPa的最高抗折强度.XRD物相分析结果表明,双掺沥青和聚丙烯纤维对该地质聚合物的物相结构没有造成影响.SEM结合断裂韧度计算结果发现纤维与地质聚合物基体结合紧密,纤维的拔出长度较长,表明聚丙烯纤维可以提高试件的断裂韧度,达到增韧效果.     

国内外近期有关胶粘剂文献的增注题录(续)

02 - 1 0 3　具有最佳粘合性、亲水性压敏胶的制备　 [此专利制法能使制备的胶粘剂具有特殊的、最佳的粘合性性能 ,它是由亲水性聚合物和辅助性短链增塑剂构成 ,其中亲水性聚合物和增塑剂之间相互以氢键和静电结合 ,并以一定的配比使该胶粘剂关键性能 ,如粘合强度 ,内聚强度和亲水性能等最佳化。该胶应用范围很广 ,例如用作皮肤及其他人体表面的生物粘合剂 ,就此而言 ,它用于药物传输体系 (例如 ,局部、经皮、经粘膜、由离子透入等药物传输体系 )、皮肤医疗包扎、伤口愈合产品和生物医学电极等 ]ＦｅｌｄｓＴｅｉｎＭｉｋｈａｉｌＭ ,ｅｆａ…     

养护温度对粉煤灰基矿物聚合物强度影响的研究

研究了不同养护温度下粉煤灰基矿物聚合物的抗压强度，以及经过1d高温养护后常温条件下强度的发展特点。结果表明：提高养护温度可以提高粉煤灰基矿物聚合物的抗压强度，缩短养护时间。同时，其强度提高程度因激发剂溶液种类不同而不同，5MK2SiO3溶液的提高程度最高；其它3种激发剂的提高幅度较小，高温养护7d时的强度与常温28d时的强度接近。     

高性能M5纤维的研究现状

介绍了一种新型刚性棒状高性能纤维聚[2,5-二羟基-1,4-苯撑吡啶并二咪唑](PIPD,商品名称为M5)的合成、结构与性能以及应用前景。研究结果表明:与PBO纤维相比,M5纤维具有抗压强度高和抗压模量高的优点,将主要应用于军事装备领域。     

Interdiffusion and crosslinking in thermoset latex films

Thermoset latex systems represent an attractive approach to obtaining the high performance needed in many different kinds of industrial coatings, while satisfying the growing requirement for environmental friendliness. In these coatings in the dispersed state, the reactive groups are packaged inside of polymer particles. These latex particles deform as the coating dries to form a transparent binder phase. The useful properties of mechanical strength, as well as scrub and solvent resistance, develop over time. This paper focuses on the idea that to achieve the desired properties in a thermoset latex coating, one has to pay proper attention to the relative rates of polymer diffusion and crosslinking in the coating. Strength in these films develops as a consequence of chains that connect crosslink points on opposite sides of interface formed between adjacent particles in the film. Thus polymer diffusion must precede extensive bond formation created by the crosslinking chemistry. This paper reviews fundamental concepts and then describes experiments in three separate systems. These experiments show that the formulator has three main strategies to vary the relative rates of these processes: 1. Catalyst strength and concentration will affect the reaction rate. 2. Polymer chain length will affect the polymer diffusion rate. 3. Temperature changes will normally have a larger affect on the polymer diffusion rate than on the crosslinking reaction rate. Presented at the 79th Annual Meeting of the Federation of Societies for Coatings Technology, on November 3, 2001, in Atlanta, GA. Department of Chemistry, Toronto, Ont., M5S 3H6, Canada.     

Physical Properties of Polymer Solids and Control of Supermolecular Structure

Abstract

Linear crystalline polymers can be processed to produce high degrees of orientation, sufficient to produce drastic increases in tensile strength and modulus. Ultra high modulus and strength fibers are produced from a high molecular weight polymer employing a variety of techniques, such as meltspinning, super-drawing, solid-state extrusion, etc. Long polymer chains can be fairly well aligned and extended only after the polymeric chains are disentangled. Gel spinning is one of the preparation techniques of disentangled high molecular weight polymer with sufficient drawability.     

AI polymer laminates for high temperature stability

Amoco AI amide imide polymer is an all aromatic polymer which is currently being used as a high temperature wire enamel. It also looks promising as a high temperature laminating material. It is available in a stable solid form and is readily formulated in its laminating solvents. B-Staged coated glass cloth with excellent shelf stability is easily prepared. AI laminates retain their initial flexural strength after four weeks at 500°F. They retain 50% of their initial flexural strength after one week at 572°F. Other modifications of this type of polymer are being investigated as laminating materials.     

Effect of hydrogen bonding and moisture cycling on the compressive performance of poly-pyridobisimidazole (M5) fiber

A clear correlation between the degree of intermolecular hydrogen bonding (H-bonding) and axial compressive strength of pyridobisimidazole (M5) as-spun fiber specimens subjected to varying annealing conditions has been established by means of Fourier transform infrared microspectroscopy and single fiber elastica loop testing. As the water initially contained in the as-spun fiber is removed by heat treatment, improvements in polymer chain orientation promote the formation of intermolecular H-bonds, leading to enhanced fiber compressive strength values. M5 fiber specimens with the highest degree of intermolecular H-bonding of 96 ± 1% are found to have a compressive strength of 1.72 ± 0.09 GPa. Moisture cycling experiments of M5 annealed specimens have provided direct evidence of partial H-bond reversibility in this material, as saturation of M5 annealed fiber resulted in the reduction of the degree of intermolecular H-bonding from 93 to 64%. Upon drying the fiber at 120 °C in an inert atmosphere, the degree of H-bonding returned to the original value of 93%. However, repeated fiber moisture cycling resulted in a monotonic reduction in the degree of H-bonding in both the saturated condition (53%) and dry state (62%). The compressive strength of saturated and dried specimens after moisture cycling was found to be statistically equivalent at a reduced level of 1.29 GPa. The original degree of H-bonding and compressive strength could be recovered by re-annealing the fiber under tension.     

Durability of PBI adhesive bonded joints under various environmental conditions

Structural adhesives are finding increasing use in many applications. However, their utilization at elevated temperature has always been a challenge due to their low thermal and mechanical properties. However, in recent years, the development of high performance polymers have overcome the problem of using adhesive bonding at high temperature to some extent. Polybenizimidazole (PBI) is one such recently emerged high performance polymer with excellent thermal and mechanical properties. It has a tensile strength of 160 MPa and a glass transition temperature (T_g) of 425 °C. Due to its excellent thermal and mechanical properties, it has the potential to be used as an adhesive under various environmental conditions. In the present work, efforts are devoted to explore the potential of using PBI at high temperature and in hot-wet environmental conditions. M21 and DT120 epoxy based carbon fiber composite bonded joints were prepared and tested. Both M21/carbon composite and DT120/carbon composite have exhibited a reduction in joint strength of about 16% and 25% respectively after 1000 h of conditioning in a hot-wet environment. However, a reduction in lap shear strength of 52% and 56% is observed when composite bonded joints were tested at 80 °C.     

Structure and properties of microcomposites and macrocomposites from block polymers

The incorporation of a rubber phase in glassy polymers, as is well known in the case of high impact polystyrene, leads-to an increase in their impact strength. Block polymers offer three principal approaches for obtaining multiphase glassy polymers in which an elastorner phase is present in the matrix of the glassy polymer. They are: (1) control ofblock polymer composition, (2) blending of block polymer with homopolymers, and (3) polymerization of a solution.of a block polymer in the monomer corresponding to one of the blocks. The observed properties, such as impact strength, modulus, and heat distortion temperature, desired in rubber modified glassy polymers are discussed for block polymer systems prepared using the above approaches.     

High strength disclinations in liquid crystalline polymers with X-shaped two-dimensional mesogenic units

Textures of liquid crystalline polymers with two-dimensional mesogens have been investigated by using polarizing optical microscopy. Disclinations, strength |S| up to 3/2 and 5/2, were found easily in each sample. Occasionally, even high strength disclination pair can be found. These high strength disclinations are very sable in high temperature although they are energy unfavorable according to the theory of Nehring and Saupe. The rare textures may be ascribed to the unique shape of the molecular mesogenic units. The stability of the high strength disclination is attributed to the energy dispersion and high viscosity in polymer melt.     

Semi-interpenetrating gel polymer electrolyte based on PVDF-HFP for lithium ion batteries

Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based gel polymer electrolyte (GPE) is considered one of the promising candidate electrolytes in the polymer lithium ion battery (LIB) because of its free standing, shape versatility, security, flexibility, lightweight, reliability, and so on. However, the pristine PVDF-HFP GPE cannot still meet the requirement of large-scale LIBs and other electrochemical devices due to its relatively low ionic conductivity and deterioration of mechanical strength caused by the incorporation of organic liquid electrolyte into the polymer matrix as well as high cost. In order to overcome above deficiencies of PVDF-HFP based GPE, ultraviolet (UV)-curable semi-interpenetrating polymer network is designed and synthesized through UV-irradiation technique, and the as-prepared semi-interpenetrating matrix is constituted by pentaerythritol tetracrylate polymer network and PVDF-HFP. The ionic conductivity of the optimized GPE is as high as 5 × 10⁻⁴ S/cm and electrochemical window is up to 4.8 V at room temperature. Especially, the LIB prepared by GPE shows the high initial discharge specific capacity of 151 mAh/g at 0.5 C and good rate capability. Therefore, the semi-interpenetrating GPE based on PVDF-HFP exhibits a promising prospect for the application of rechargeable LIBs.