Crystal lattice deformation in single poly(p-phenylene benzobisoxazole) fibres

The relationships between distortion of the crystal lattice with deformation and fibre mechanical properties are complex. Micro-focus synchrotron diffraction is an ideal tool for probing such relationships. The investigation of fibres with different processing histories enables the influence of processing to be assessed. Longitudinal and transverse crystal strain is examined for three different varieties of PBO fibre (AS, HM and HM+). Large variations are found to exist between the different fibre types, although they share the same chemical structure.Crystal modulus calculated from longitudinal crystal strain and stress is found to be lowest in the fibre with the highest tensile modulus (HM+). Deformation increases the a-axis dimension of the unit cell for PBO AS and HM whilst decreasing both the a- and b-dimensions for HM+. These effects have been attributed to molecular chain rotation. It is also observed that the unit cell angle increases with deformation and the rate of change in unit cell volume is consistent between all fibre types, regardless of processing history.     

High-Strength,Thin PBO Nanofiber Membrane with Long-Term Stability for Osmotic Energy Conversion

Ion-selective membrane embedded in a reverse electrodialysis system can achieve the conversion of osmotic energy into electricity. However, the ingenious design and development of pure polymer membranes that simultaneously satisfy excellent mechanical strength, long-term stability, high power density, and increased testing area is a crucial challenge. Here, high-strength, thin PBO nanofiber membranes (PBONM) with 3D nanofluidic channels and a thickness of 0.81 µm are prepared via a simple vacuum-assisted filtration technology. The thin PBONM exhibits excellent mechanical properties: stress of 235.8 MPa and modulus of 16.96 GPa, outperforming the state-of-the-art nanofluidic membranes. The obtained PBONM reveals surface-charge-governed ion transport behavior and high ion selectivity of 0.88 at a 50-fold concentration gradient. The PBO membrane-based generator delivers a power density of 7.7 and 40.2 W m⁻² at 50-fold and 500-fold concentration gradient. Importantly, this PBONM presents excellent stability in response to different external environments including various saline solutions, pH, and temperature. In addition, the maximum power density of PBONM reaches up to 5.9 W m⁻² under an increased testing area of 0.79 mm², exceeding other membrane-based generators with comparable testing areas. This work paves the way for constructing high-strength fiber nanofluidic membranes for highly efficient osmotic energy conversion.     

多壁碳纳米管/聚亚苯基苯并二噁唑复合材料的微结构与性能

以甲基磺酸(MSA)为溶剂通过溶液共混法制备了不同多壁碳纳米管(MWNTs)含量的多壁碳纳米管/聚亚苯基苯并二噁唑(MWNTs/PBO)复合材料, 用扫描电镜(SEM)对热处理前后复合材料的微结构进行了分析, 并对其导电、力学和耐热性能进行了研究。结果表明: MWNTs能均匀地分散在聚合物基体中, 并能形成一定的网络结构, 热处理后的复合材料较热处理前的结构更致密, 导电性能和力学性能都有所改善, 其中MWNTs质量分数为10％的热处理后复合材料与纯PBO聚合物相比, 体积电阻率降低约9个数量级, 而拉伸强度和拉伸模量分别提高了95％和53％, 耐热性能也有一定的提高。      

AB型PBO的新单体合成与聚合反应研究

以4-氨基-6-硝基间苯二酚盐酸盐(ANR·HCl)和对甲氧羰基苯甲酰氯(MBC)为原料,合成了自缩聚AB型PBO的新单体-2-(对甲氧羰基苯基)-5-氨基-6-羟基苯并噁唑(MAB),研究了在多聚磷酸介质中新单体的聚合反应,获得了聚对苯撑苯并二噁唑(PBO)树脂.结果表明:采用经ANR·HCl和MBC的缩合、环合再脱水的原位合成工艺先制得2-(对甲氧羰基苯基)-5-硝基-6-羟基苯并噁唑,再对硝基催化加氢是合成MAB的优选路线,总收率为71.14%;制得的MAB稳定性良好、空气中放置300天纯度仅下降0.15%,在玻璃仪器中对98.88% MAB进行均缩聚反应、无需加抗氧剂即可得到特性粘数接近1 L·g-1的PBO树脂,缩聚时间降至18 h,已具有操作方便和易实施PBO产业化等特点.     

Novel developments in the multidimensional characterization of segmented copolymers

Controlled radical polymerization (CRP) provides the polymer chemist with the ability to produce tailor-made polymers with controlled molar masses, molar mass distributions, chemical compositions and macromolecular architectures. Segmented copolymers can be synthesized having polymer segments arranged in a linear fashion (linear block copolymers), however, polymer segments can also be attached to pre-synthesized macromolecules or to multifunctional core molecules to produce branched (graft) copolymers, polymer stars or dendrimers. Although there are many ways to control the chain growth and the architecture of the target macromolecules, side reactions cannot be completely avoided. Accordingly, even with CRP, obtained products exhibit chemical composition and topology distributions along with the molar mass distribution.     

Environmental effects on poly‐p‐phenylenebenzobisoxazole fibers. I. Mechanisms of degradation

This is the first of a two‐part series investigating the degradation mechanisms of PBO fiber and approaches to alleviating degradation and improving fiber properties. Poly‐p‐phenylenebenzobisoxazole (PBO) fiber is a high strength and modulus fiber with remarkable thermal stability. Recent in‐service failures of this fiber have revealed that the fiber degrades rapidly in relatively mild environmental conditions of moisture and heat. In this work the mechanisms of degradation due to moisture, the presence of acid, and the effect of radiation from the UV–vis spectrum are investigated. It is found that exposure to moisture results in the loosening of the fiber morphology leading to an increase in the number and size of defects. The presence of aqueous acid causes both loosening of the fiber structure and hydrolysis of the oxazole ring structure. The effect of UV–vis radiation is primarily hydrolysis of the material near the fiber surface with attendant formation of amide linkages. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3517–3525, 2006     

电晕处理对高性能PBO纤维的表面性能及其界面粘接性能的影响

对高性能PBO纤维表面进行了电晕处理,优化了其处理工艺。用XPS,FT-IR和SEM研究了处理前后纤维表面化学结构及物理结构的变化,通过单丝拔出试验和短梁剪切试验评价了PBO纤维与树脂基体的微宏观界面粘接性能。结果表明:经电晕处理后,PBO纤维表面含氧量增多,表面浸润性得到改善,单丝拔出的PBO-环氧界面剪切强度(IFSS)提高了25.6 ％,但短梁剪切强度(ILSS)的提高不明显。     

2，2′-（1，3-亚苯基）双（2-噁唑啉）的合成研究

探讨了由间苯二甲腈和一乙醇胺在氯化锌催化下合成2,2′-(1,3-亚苯基)双(2-噁唑啉)的方法.操作条件:间苯二甲腈与一乙醇胺的摩儿比为1:2,催化剂的量为腈的2.5%、反应时间5 h,反应温度为140 ℃,使产品收率达85%.     

PBO纤维研究进展

聚对苯撑苯并双口恶唑（PBO）纤维是一种高性能纤维,具有强度高,模量大,热稳定性好等性质,因而在合成材料,国防军事等领域具有广泛的用途。本文重点介绍了PBO纤维的制备,性能与应用方面的研究进展。     

Synthesis,characterization of new carboxylic acid‐containing benzoxazine and its cocuring behaviors with bisoxazoline

A new benzoxazine‐benzoic acid (BBA) was synthesized and the structure was conformed by ¹H‐NMR, ¹³C‐NMR, FTIR, etc. The cure behavior of BBA and cocure behavior of BBA with phenylene bisoxazoline (1,3‐PBO) were investigated by differential scanning calorimetry (DSC). It was found that BBA showed a single curing exothermic peak at about 217°C. However, all BBA/1,3‐PBO systems exhibited two exothermic peak. One may be attributed to the reaction between carboxyl groups of BBA and 1,3‐PBO. And the other was attributed to the ring‐opening polymerization of oxazine rings and the reaction between phenolic hydroxyl groups generated by the ring opening of benzoxazine ring and 1,3‐PBO. The curing temperature of benzoxazine containing carboxyl groups could be lowered by the copolymerization of 1,3‐PBO. Thermogravimetric analysis showed that the incorporation of ester–amide groups had a significant effect on decreasing thermal stability and char yield of the cured resin. SEM results indicated that 1,3‐PBO could toughen BBA benzoxazine resin. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011