Pretreating poly(p‐phenylene benzobisoxazole) fibre with polyphosphoric acid and dyeing with disperse dyes

In recent years, many advanced composite materials based on poly(p‐phenylene‐2,6‐benzobisoxazole) fibres have become prominent in applications requiring high‐strength and flame‐retardance such as body armour, industrial reinforcement materials and military camouflage. However, the application of these fibres used as protective clothing is limited due to difficulties in dyeing and printing. In the present work, a process for pretreating poly(p‐phenylene benzobisoxazole) fibre with polyphosphoric acid was applied, and the pretreated fibre was then dyed with disperse dyes via dip dyeing. Effects of pretreatment temperature and time on structure and properties were investigated. Surface morphology, crystallinity, chemical structure and degree of orientation of fibres were characterised. The results indicated that the supramolecular structure of the fibre was relaxed or swelled by polyphosphoric acid in the pretreatment process, so that the dyeability of poly(p‐phenylene benzobisoxazole) fibre was improved, with satisfactory dye exhaustion, K/S values and dyeing fastness. Also, with the appropriate pretreatment process, the swelling effect of polyphosphoric acid on the structure of poly(p‐phenylene benzobisoxazole) fibre was limited, so as to control the decrease in tensile strength and limiting oxygen index of the dyed fibre.     

Fabrication of uvioresistant poly(p-phenylene benzobisoxazole) fibers based on hydrogen bond

The poly(p-phenylene benzobisoxazole) (PBO) fiber with excellent performance is vulnerable to the irradiation of UV light, which significantly limits their application in advanced composites. Therefore, finding feasible and efficient ways to improve the uvioresistant properties of PBO fiber is of significance. In this work, a facile one-pot method is developed for continuously preparing the PBO/poly(2,5-dihydroxy-1, 4-phenylpyridimidazole) (PIPD) copolymer fiber to greatly enhance the anti-UV properties of PBO fibers. The experimental results demonstrate that the fabricated PBO/PIPD copolymer fiber (molar ratio of 7:1) with greatly improved surface wetting properties (the maximum increase can reach about 179%) possesses satisfactory and desired uvioresistant performance, which is 30.8% higher than that of pure PBO fibers after 480 h UV aging irradiation. The fabricated PBO/PIPD copolymer fiber with improved UV stability has the potential to be applied to many important application areas even in a severe and harsh environment. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48432.     

Graphitization of highly porous carbons derived from poly(p-phenylene benzobisoxazole)

We studied the development of graphitization in carbonaceous materials derived from poly(p-phenylene benzobisoxazole) (PBO) pre-activated with carbon dioxide to burn-off degrees of 15 and 51 wt.%. The activated materials were subsequently heat-treated at various temperatures comprised between 1600 and 2700 °C. The changes in porous texture, structure and nanostructure were characterized by gas adsorption analysis, X-ray diffraction, Raman spectroscopy and high-resolution transmission electron microscopy. The two sets of materials pre-activated to different degrees of burn-off exhibited similar changes as a function of the heat treatment temperature. Quite unexpectedly, the presence of porosity generated by physical activation of PBO chars does not affect their graphitizability. The materials seem to retain a sufficiently large degree of the order acquired during the spinning of the PBO fibres to allow the remaining bi-periodic structural units to re-arrange, allowing subsequent graphitization.     

Study on photoaging of poly(p‐phenylene benzobisoxazole) fiber

As a kind of rig‐rod‐like polymer, poly(p‐phenylene benzobisoxazole) (PBO) has received great interest because of its excellent mechanical properties and good thermal stability. The use of PBO fibers, however, is limited due to its low sunlight stability. In this work, the photoaging of PBO fibers, as well as the effects of oxygen and moisture on their photoaging, is investigated by tensile strength measurements, infrared spectroscopy, molecular mass determination, and scanning electron microscopy. It is first time to find that the photoaging of PBO fibers includes two development stages. The physical aging is the dominate factor at the first stage of photoaging relative to the second stage, in which the chemical aging is the dominate factor. In the first degradation stage, long defects appear and develop parallel to the fiber axis. Little chemical change occurs in this stage. In the second degradation stage, the molecular mass of PBO decreases and chemical degradation occurs. Oxygen accelerates the occurrence of chemical degradation. It is also found PBO fibers are more stable for photoaging when moisture and oxygen are isolated. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

含氯聚对苯二甲酰对苯二胺纤维的结构与性能

以邻氯对苯二胺(Cl-PPD)与对苯二甲酰氯(TPC)为单体,在N-甲基吡咯烷酮(NMP)/氯化钙(Ca Cl2)或氯化锂(Li Cl)体系中进行低温溶液聚合,合成了含氯聚对苯二甲酰对苯二胺(Cl-PPTA)溶液,直接进行湿法纺丝,制备了Cl-PPTA纤维。采用旋转流变仪测试了Cl-PPTA溶液的流变性能,利用傅里叶变换红外光谱、扫描电子显微镜、热失重分析、纤维强伸度仪、声速取向测量仪、氧指数测定仪对Cl-PPTA纤维的结构及性能进行了表征。结果表明:相比于NMP/Ca Cl2体系,NMP/Li Cl体系的Cl-PPTA溶液黏度更低,所制得的纤维其表面更光滑、结构更致密,纤维力学性能也较好;热处理后两种纤维力学性能均得到进一步改善;两种Cl-PPTA纤维具有较好的热稳定性,其阻燃性能均远高于PPTA纤维。     

聚对苯撑苯并双噁唑、芳纶纤维及其复合材料

研究了聚对苯撑苯并双口恶唑(PBO)和芳纶(F-12)2种纤维的结构、性能及其单向复合材料的性能。电子扫描电镜照片微观结构的研究表明,PBO纤维与F-12纤维相比较,其分子取向更高,表面更光滑,因而与树脂基体的粘接力较差;而F-12纤维因为分子表面不均匀,有微小的浅沟槽,与树脂基体的接触表面积较大,因而粘接力强。复合材料性能的研究表明,PBO纤维的单向复合材料比F-12芳纶纤维的具有更好的拉伸性能,其中拉伸强度高约34.7%,拉伸模量高约63.8%。但其层间剪切强度却很低,只有24.3 MPa。     

Adsorption thermodynamics and kinetics of Cr(VI) on KIP210 resin

Series of resin selection experiments were carried out and the KIP210 strong base anion exchange resin was confirmed to have the maximum equilibrium adsorption capacity to remove Cr(VI) from wastewater. The adsorption thermodynamics and kinetics of Cr(VI) on KIP210 resin were investigated completely and systematically. The static experiments were performed to study the effects of various parameters, such as shaking speed, resin dosage and pH during the adsorption process. The results indicate that the effect of external diffusion is eliminated at 160 rpm, the best pH value is 3.0 and the removal percentage of Cr(VI) increases with the increase of the resin dosage. The adsorption of Cr(VI) on KIP210 agrees well with the Langmuir isotherm and the adsorption parameters of thermodynamics are ΔH = 26.5 kJ mol⁻¹, ΔS = 126.7 J mol⁻¹ K⁻¹ and ΔG < 0. It demonstrates that the adsorption of Cr(VI) on KIP210 is a spontaneously endothermic physisorption process. Moreover, the adsorption process can be described well by a pseudo-second-order kinetic model and the activation energy is 30.9 kJ mol⁻¹. The kinetic analysis showed that the adsorption rate is controlled by intraparticle diffusion. The resin is successfully regenerated using the NaOH solutions.     

Deformation band studies of axially compressed poly(p-phenylene terephthalamide) fiber

Deformation mechanism of poly(p-phenylene terephthalamide) (PPTA) fiber during axial compression was studied. PPTA fibers were embedded in resin and axialy compressed in a tensile machine. PPTA fibers were then taken out from resin at various stages of compression. Kink band formation was examined by means of polarizing microscopy, X-ray diffraction (WAXD), electron diffraction (ED), and electron microscopy. WAXD pattern of seriously compressed PPTA fiber shows that (200) reflection spots and arcs appear on the equator and meridian respectively. On the other hand, (110) reflection spots are confined to the equator. PPTA fiber could be splitted tangentially and radially into two kinds of thin fibrillar fragments (I and II) which reveal two distinct types of kink band and ED pattern. In fragment I obtained by tangential splitting, kink bands are formed at about 55° with respect to fibril axis, whereas in fragment II obtained by radial splitting kink bands are formed perpendicular to the fibril axis. These results were confirmed by ED studies. It was assumed that slip of (200) planes containing hydrogen bonded sheets as well as intermicrofibril slip plays an important role in the deformation of PPTA fiber during axial compression.     

Encapsulation of disperse dye by phase separation technique using poly(styrene‐maleic acid)

C.I. disperse dye blue 60 was encapsulated by poly(styrene‐maleic acid) using phase separation technique, followed by the preparation of the encapsulated disperse dye dispersion. The effects of process conditions on particle size of the dispersion were investigated. The results showed that the particle size of the encapsulated disperse dye dispersion was small, and the stability was excellent when mass ratio of poly(styrene‐maleic acid) to disperse dye (R_p/d), dropping speed of phase separation agent (D_s), disperse dye content in dispersion (C_d), and dispersing time (D_t) were about 20%, 7 mL/min, 5–7.5%, and 1.5 h, respectively. Transmission electron microscope (TEM), zeta potentials, and contact angle indicated that C.I. disperse dye blue 60 was successfully encapsulated by poly(styrene‐maleic acid). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

聚苯并双噁唑类聚合物的合成及改性

简述了聚对苯撑苯并双(?)唑(PBO)的合成方法,详述了直链烯烃型、稠环芳烃型、联苯取代基型、杂环型聚苯并双(?)唑类聚合物的合成方法。综述了等离子体处理法、偶联剂处理法、电晕处理法等一系列PBO纤维表面改性技术的研究进展,通过介绍PBO／碳纳米管复合材料和PBO／粘土复合材料的合成技术,简析了PBO的纳米改性的研究。指出聚苯并双(?)唑聚合物研究将集中在合成高相对分子质量的聚合物合成技术,通过纳米改性及表面改性提高其性能,扩大应用领域。     

Correlation between the shade of an azo disperse dye on poly(ethylene terephthalate) and poly(lactic acid) fibres with its spectroscopic properties in selected organic solvents

A series of azo disperse dyes was synthesised and the purified, synthesised dyes were characterised by proton nuclear magnetic resonance, thin‐layer chromatography and melting point measurement. The spectroscopic properties of the dyes in solution were studied by dissolving the dyes in ethyl acetate and methyl benzoate. These were seen as mimicking the environment of the dye when inside dyed poly(lactic acid) and poly(ethylene terephthalate), respectively. Reflectance spectra of the dyes on both polyester substrates were also measured in order to correlate with the spectroscopic properties of the dyes in solution. The absorbance spectra of the dyes in solution exhibited a hypsochromic (lower wavelength of maximum exhaustion) shift when dissolved in ethyl acetate, compared with methyl benzoate. The occurrence of this yellow shift was attributed to the lower polarity of ethyl acetate compared with methyl benzoate. The colour of the dyes in ethyl acetate solution was also brighter and stronger (higher molar extinction coefficients) than that in methyl benzoate. Most of the synthesised dyes exhibited high levels of exhaustion onto the two polyester fabrics. However, the visual colour yields, for those dyes having approximately the same high level of exhaustion, were different, the dyed poly(lactic acid) being stronger (higher K/S value) as well as being yellower and a trace brighter than the dyed poly(ethylene terephthalate). This difference correlated well with the solvatochromic study of the dyes in ethyl acetate and methyl benzoate solution.     

聚对亚苯基苯并二噁唑(PBO)纤维的环境老化及防老化研究进展

综述了国内外聚对亚苯基苯并二噁唑(PBO)纤维老化的最新研究进展.重点介绍了国外研究PBO纤维水热老化和光照老化过程的方法以及对老化机理的推测和分析,指出通过改进纺丝工艺,完善纤维的结构以提高抗溶胀性能,选用合理的抗光氧化试剂以及对纤维进行化学改性,对纤维进行必要的物理防护等,将是今后PBO纤维抗老化的研究方向.     

Crystallization kinetics and nucleating agents for enhancing the crystallization of poly(p-phenylene sulfide)

An experimental study of crystallization kinetics and the influence of nucleating agents on the solidification of poly(p-phenylene sulfide) (PPS) is described. The effect of molecular weight is considered by investigating PPS samples having different viscosity levels. We studied the effect of a range of nucleating agents including aluminum oxide, calcium oxide, silicon dioxide, titanium dioxide, kaolin, and talc. All of these compounds were found to enhance the rate of crystallization; in particular, silicon dioxide, kaolin, and talc were the most effective nucleating agents. An effort to study particle size effects of the silicon dioxide showed that the nucleation was very sensitive to the source of the material. These studies did, however, show that nucleation rates tended to increase with decreasing particle size and increasing loading of silicon dioxide. Comparison of PPS crystallization rates with those of other polymers indicates that it crystallizes much more slowly than polyethylene or isotactic polypropylene and is slower than polyetherether-ketone, when comparisons are made on an equivalent basis. PPS crystallizes at similar rates to polyethylene terephthalate (PET). However, our nucleated PPS does not crystallize as rapidly as nucleated PET.     

原花青素在HZ818树脂上的吸附热力学和动力学

通过在不同温度下的静态吸附实验,研究了葡萄籽原花青素在大孔树脂HZ818上的吸附热力学及动力学特性。分别采用Langmuir、Freundlich等温式对不同温度下的等温吸附数据进行拟合,采用Largergren拟一级动力学模型、拟二级动力学模型和颗粒内扩散动力学模型对吸附动力学数据进行分析。结果表明:原花青素在HZ818树脂上的吸附量随着温度的升高而增大,等温吸附数据更符合Langmuir等温吸附方程,吸附焓变大于0,吉布斯自由能变小于0,HZ818树脂对原花青素的吸附过程为自发进行的吸热过程;吸附动力学更符合拟二级动力学模型,过程受主要包括颗粒内扩散在内的多因素共同影响。     

Electrosynthesis of conducting poly(p-phenylene)

The polymerization of benzene was studied in bulk and in nitrobenzene using BF₃O (C₂H₅)₂ as a supporting electrolyte at platinum electrodes to obtain poly(p-phenylene). The polymers were formed as a black thready mass on the anode and their yields were restricted to the area of the anode in the electrochemical cell. The yields of the polymers formed in the bulk and in nitrobenzene were almost equal, although electrical resistances of the polymers obtained from the bulk were relatively lower. Cyclic voltammetry measurements suggest that the polymerization of benzene took place from the species generated anodically in situ. © 1993 John Wiley & Sons, Inc.     

Adsorption thermodynamics and diffusion of disperse anthraquinone dyes in acetate fibre

Diffusion coefficients, thermodynamic parameters and adsorption equilibrium isotherms of some anthraquinone dyes for acetate fibre are reported. The chemical constitution seems to be more important than the size factor in determining dye diffusion into the interior of the fibres. The activation energies of diffusion decreased strongly when o-dichlorobenzene was present, due to the plasticising effect of carrier. Nernst partition isotherms were obtained, up to saturation. Substantivity decreased when water-solubilising groups are present in the molecule.The aqueous solubilities and heats of solution have been measured; the higher ΔH_w values were found for the derivatives which can form intermolecular hydrogen bonding in the crystalline state.     

聚对苯撑苯并双噁唑纤维改性方法的研究进展

简单介绍了聚对苯撑苯并双噁唑(PBO)纤维的性能与应用,重点阐述了低温等离子处理法、酸碱处理法、偶联剂处理法、辐射处理法和共聚改性法5种常用的PBO纤维改性方法的研究情况。综述表明,无论采用何种改性方法,都能相应有效改善纤维的表面性能,提高纤维与其它材质间的黏结性。同时,指出每种改性的方法都存在一定的缺陷。     

Crystallization kinetics of poly(l-lactic acid)

The morphology and crystal growth of poly(l-lactic acid), PLLA have been studied from the melt as a function of undercooling and molecular weight using hot stage microscopy. Attention has been given to the application of growth rate equation on the growth rate data of PLLA and thus various nucleation parameters have been calculated. The criteria of Regime I and Regime II types of crystallization has been applied for the evaluation of substrate lengths.     

Electronic processes in poly(p-phenylene) and related compounds I. Paramagnetic and electrical properties of doped poly(p-phenylene)

Poly(p-phenylene) (PPP) was prepared by polymerization of benzene and was exactly purified from oligomers and the catalyst. IR spectra of the resulting material indicated only para substitution and a DP about 20. PPP is a polycrystalline substance with a small degree of crystallinity and is thermally resistant up to 798 K. The annealing of pristine polymer produced a material with higher crystallinity and crystallite size. In our investigations we examined the electrical properties of doped (AlCl₃) and undoped PPP at different temperatures. The mechanism of conductivity is explained assuming the existence of the Schottky barriers between polycrystalline grains and intergrain regions. The WAXS and ESR data are compared with the electrical results.     

Nonisothermal crystallization kinetics and morphology of poly(ethylene terephthalate) modified with poly(lactic acid)

The nonisothermal crystallization kinetics of poly(ethylene terephthalate) (PET) copolymers modified with poly(lactic acid) (PLA) were investigated with differential scanning calorimetry, and a crystal morphology of the samples was observed with scanning electron microscopy. Waste PET (P100) obtained from postconsumer water bottles was modified with a low‐molecular‐weight PLA. The PET/PLA weight ratio was 90/10 (P90) or 50/50 (P50) in the modified samples. The nonisothermal melt‐crystallization kinetics of the modified samples were compared with those of P100. The segmented block copolymer structure (PET‐b‐PLA‐b‐PET) of the modified samples formed by a transesterification reaction between the PLA and PET units in solution and the length of the aliphatic and aromatic blocks were found to have a great effect on the nucleation mechanism and overall crystallization rate. On the basis of the results of the crystallization kinetics determined by several models (Ozawa, Avrami, Jeziorny, and Liu–Mo) and morphological observations, the crystallization rate of the samples decreased in the order of P50 > P90 > P100, depending on the amount of PLA in the copolymer structure. However, the apparent crystallization activation energies of the samples decreased in the order of P90 > P100 > P50. It was concluded that the nucleation rate and mechanism were affected significantly by the incorporation of PLA into the copolymer structure and that these also had an effect on the overall crystallization energy barrier. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007