Preparation of High Strength and Toughness Aramid Fiber by Introducing Flexible Asymmetric Monomer to Construct Misplaced-Nunchaku Structure

High performance fibers with high strength and toughness have great potential in composites, but contradiction between tensile strength and elongation at break makes the preparation to become a current challenge. Herein, an asymmetric structure of more flexible diamine, 3,4′-diaminodiphenyl ether (3,4′-ODA), is introduced into heterocyclic aramid (PBIA) fibers to replace rigid symmetric p-phenylenediamine (PDA). By studying the properties of copolymer (mPEBA) fibers with different ratios of diamine, it is found that the mPEBA fiber reached the optimal mechanical properties with the 30% content of 3,4′-ODA. Compared with homopolymerized heterocyclic aramid fibers, the tensile strength and elongation at break of mPEBA fiber are improved by 26.2% and 38.7%, respectively. Results of X-ray diffraction show that the introduction of 3,4′-ODA structure can increase stretchability of mPEBA fibers, improving the orientation degree during hot-drawing. Molecular dynamics simulations confirm that 3,4′-ODA structure undergoes a conformation transformation to form a straightened chain during hot-drawing, while symmetrical 4,4′-diaminodiphenyl ether (4,4′-ODA) cannot form the same conformation. The misplaced-nunchaku structure is formed based on the special meta-para position of 3,4′-ODA, achieving the synergy of high strength and high toughness.     

Zirconium-Embedded Polyhedral Oligomeric Silsesquioxane Containing Phosphaphenanthrene-Substituent Group Used as Flame Retardants for Epoxy Resin Composites

A zirconium hybrid polyhedral oligomeric silsesquioxane derivative (Zr–POSS–bisDOPO) is synthesized by the corner-capping and Kabachnik–Fields reactions. It is characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR), and then used as a flame retardant in diglycidyl ether of bisphenol A (DGEBA) to endow epoxy resin (EP) with flame retardancy. The flame retardancy, thermal stability, and mechanical properties of the cured EP/Zr–POSS–bisDOPO composites are investigated. The results show that when Zr–POSS–bisDOPO is added by 5–7 wt%, the EP/Zr–POSS–bisDOPO composites pass the UL-94 V-0 rating test. In addition, they have a better flame-retardant effect than pure EP. The combination of Zr atom embedded in the Si O cubic cage and the two phosphaphenanthrene substituent groups in one corner of cubic cage is expected to realize the Zr/Si/P ternary intramolecular hybrid synergistic effect and achieve the possibility of dispersing metal–POSS cages at a sub-micrometer-scale level into polymer matrix. It also proves that Zr–POSS–bisDOPO produces phosphorus-containing free radicals and terminates the chain reactions in gas phase. Meanwhile the Si O Si and Zr O units are retained in the solid phase, which promote the char formation and enhance the flame retardancy. This kind of Zr-doped POSS will be helpful for developing the new metal–POSS hybrid flame-retardant and polymer composites.     

Bioderived Bilayer Shell Modification β-FeOOH Nanorods via Self-Assembly Technique as Sustainable Flame Retardants for Enhancing Flame Retardancy of Epoxy Resin

The design and application of bioderived flame retardants have been widely conducted to meet the concept of green and sustainable development. Here, self-assembly technique is used to prepare core–shell bioderived additives by using β-FeOOH as the core and polydopamine (PDA)/tannic acid (TA) bilayer as the shell, following adsorption of nickel ions to enhance the thermal stability, flame retardancy, and mechanical properties of epoxy resin (EP). The molecular structure of biobased resources is rich in hydroxyl groups and carbon content, which can be dehydrated and carbonized during combustion and promote the formation of robust protective char layer. With the addition of 5 wt% β-FeOOH@PTNi, the EP composites can pass V-0 rating in the UL-94 test. The peak heat release rate and total heat release decrease by 28.4% and 17.4% compared with pure EP. The bioderived nanorods can capture the oxygen free radicals, contributing to flame retarding in gaseous phase. Thus, the release of high-toxic CO and flammable gaseous is significantly suppressed. Besides, the storage modulus of EP composites increases by 16.0% with the addition of 5% β-FeOOH@PTNi compared with pure EP. This work provides a sustainable methodology for the design of bioderived flame retardants for EP.     

Crude Wax Extracted from Rice Bran Oil Improves Oleogel Properties and Oxidative Stability

Crude wax extracted from rice bran oil (RBO) is used to improve the oleogel properties and oxidative stability of RBO. The effect of crude rice bran wax (CrBW) on the formation characteristics and oxidative stability of oleogels is discussed. The results show that oleogels can be formed with 7.0 wt% CrBW at 20 °C. As the concentration of CrBW increases from 7.0 to 11.0 wt%, the hardness and solid fat content (SFC) of the oleogels increase significantly, and the oleogels are primarily β' crystals. Moreover, oleogel crystals formed with 5 and 7 wt% CrBW are flocculent; when the amount included is 9%, the oleogel crystals are transformed into long dendrites, and the density rises. After 90 days of storage at 20 °C, the peroxide value of oleogels formed with 9.0 wt% CrBW slowly rises from 3.21 to 6.52 mmol kg⁻¹. Practical Applications: Oleogels prepared here by CrBW and RBO are an innovative structural lipid without trans fats. Useful information on the rich fats and nutrients in CrBW is provided, which reduces the production cost and improves the industrial production capacity.     

蒽醌法合成过氧化氢催化剂的研究进展

过氧化氢（H₂O₂, 俗称双氧水）, 由于其强氧化性常用作漂白剂、消毒剂, 同时也作化工原料。目前工业上生产过氧化氢的主要方法为蒽醌法, 全球近99%的产品均通过蒽醌法制得。研究具有高活性、高选择性及经济性的催化剂是合成过氧化氢所面对的最具挑战性的课题, 同时也是工业催化领域的研究热点之一。主要针对蒽醌法制过氧化氢催化剂, 综述了各种活性组分、载体及助剂在蒽醌加氢催化剂中的研究进展, 并简单探讨了各种活性组分的优缺点, 概括了各种载体、助剂的作用, 以期对过氧化氢催化剂的合成制备提供一些有益的启示。     

DD—921钢铁常温发黑剂的研制和应用

研究了钢铁常温发黑过程的成膜机理,各组分之间的作用以及相互之间的影响,着重分析了常温发黑的优缺点,工艺控制参数以及经济性。     

DECOMPOSITION AND PRECIPITATION OF CARBIDES IN HOT-ROLLED Si-Fe SHEETS

在高温金相显微镜下,直接观察碳化物在热轧硅钢中的分解与析出过程。指出冷却速度对碳化物析出形态有很大影响。用差热分析确定了碳化物的分解与析出温度。所得结果为改进热轧硅钢生产工艺提供了重要的依据。     

大型钛合金压气机盘超塑性等温锻造模具结构及工艺参数实验研究

通过超塑拉伸和压缩试验，用金属铅进行模拟实验，探讨了大型ＴＣ１１合金压气机盘超塑性等温锻造的工艺参数，模具结构，锻坯形状尺寸及润滑剂的选择、并讨论了其模具材料及加热方式的选择。     

LD7铝合金时效工艺的研究

通过试验系统地研究了ＬＤ７铝合金的单级和两级时效工艺。结果表明，与传统的单级时效相比，两级时效在不降低室温强度，硬度的前提下，可显著提高合金的电导率及高温性能。     

全军表面工程推广网表面技术应用实例

本文根据96年各表面工程推广站技术工作总结中反映的情况，整理出各站在主要表面技术：电刷镀、热喷涂和粘接粘涂方面的应用实例．反映建站以来各站在装备维修中推广应用表面工程技术的实际状况和取得的主要成绩。