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31.
海藻酸钠TEMPO改性及其在造纸中的应用初探 总被引:1,自引:0,他引:1
钙离子对实现造纸白水封闭循环有关键性的制约作用。通过对天然海藻酸钠进行改性来制备高羧基含量的化学助剂用于造纸湿部,可以起到控制钙离子影响的效果。通过测定2,2,6,6-四甲基哌啶-1-氧自由基(TEMPO)改性海藻酸钠羧基含量和螯合值,分析研究了NaClO用量、pH值和温度对反应过程的影响。选取氧化后羧基含量为2.14%、3.61%和未氧化(1.96%)的三组海藻酸钠添加到造纸湿部中进行应用实验,结果表明在一定的添加量下海藻酸钠能提高纸料的留着、滤水性能,并同时提高纸张强度。海藻酸钠加入量0.02%时最佳,并且羧基含量为3.61%的改性海藻酸钠作用效果最好。 相似文献
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This article is a duplicate of an article previously published in the Journal of Applied Polymer Science, Vol. 99, No. 6, March 15, 2006, pp. 3062‐3069 http://doi.wiley.com/10.1002/app.22908 . We regret any inconvenience this may have caused. 相似文献
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A series of semicrystalline diblock copolymers of poly(4-vinylpyridine-b-?-caprolactone) (P4VP-b-PCL) have been synthesized by the living ROP of CL followed by the TEMPO polymerization of 4-VP. Depending on the relative block length and different solvent compositions, these copolymers self-assemble into different supramolecular structures in toluene/dichloromethane (DCM) solution, including spherical micelles, bowl-shaped vesicles, multilayer vesicles, porous spheres, and large compound micelles. In methanol/DCM solution system, the crystalline PCL core disturbs the balance of free energy, thus results in a series of morphological changes including spherical micelles, worm-like rods, vesicles, coexisted vesicles and lamella, and finally platelet lamella. 相似文献
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为高效获得医药中间体桦木酸,以2,2,6,6-四甲基哌啶-氮-氧化物(TEMPO)为催化剂,使用非金属选择性氧化桦木醇,在氧化28位碳上羟基的同时,避免氧化其他基团。确定最优工艺条件为:使用二溴海因作氧化剂,反应温度为25℃,反应时间为1 h,最后得率可达72%。本反应为单一相反应,不需使用相转移催化剂。不但提高了产率,且大大缩短了反应时间,同时使反应条件更加温和。 相似文献
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Redox shuttle electrolyte additives have been suggested as a possible mean of internal overcharge protection of secondary lithium-ion batteries. TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) is one of these redox shuttles for overcharge protection of 3 V class Li-ion cells. The electrochemical reversibility and the diffusion coefficient of this molecule has been evaluated by mean of cyclic voltammetry. The redox shuttle voltage was found to be 3.5 V versus Li/Li+ and D = cm2 s−1. The electrochemical stability of TEMPO in different overcharging conditions has been evaluated by long-term cycling using Li/Li4Ti5O12 cells. Results show that the TEMPO redox system does not act as an ideal shuttle. When dissolved in the electrolyte at 0.5 M, this additive is able to level off the cell potential at 3.5 V for a long period at low overcharging current (C/200 to C/50). Nevertheless, it appears that the cell capacity fades drastically at the first cycles and with time. This phenomenon is probably related to the stability of the oxidized and reduced form of the TEMPO molecule. 相似文献
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Cheng‐Xia Miao Liang‐Nian He Jin‐Quan Wang Jing‐Lun Wang 《Advanced Synthesis \u0026amp; Catalysis》2009,351(13):2209-2216
An effective catalytic system comprising a 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) functionalized imidazolium salt ([Imim‐TEMPO]+ X−), a carboxylic acid substituted imidazolium salt ([Imim‐COOH]+ X−), and sodium nitrite (NaNO2) was developed for the aerobic oxidation of aliphatic, allylic, heterocyclic and benzylic alcohols to the respective carbonyl compounds with excellent selectivity up to >99%, even at ambient conditions. Notably, the catalyst system could preferentially oxidize a primary alcohol to the aldehyde rather than a secondary alcohol to the ketone. Moreover, the reaction rate is greatly enhanced when a proper amount of water is present. And a high turnover number (TON 5000) is achieved in the present transition metal‐free aerobic catalytic system. Additionally, the functionalized imidazolium salts are successfully reused at least four times. This process thus represents a greener pathway for the aerobic oxidation of alcohols into carbonyl compounds by using the present task‐specific ionic liquids in place of the toxic and volatile additive, such as hydrogen bromide, bromine, or hydrogen chloride (HBr, Br2 or HCl), which is commonly required for the transition metal‐free aerobic oxidation of alcohols. 相似文献
37.
A system similar to an interpenetrating polymer network (IPN), based on polyethylene/poly(methylmethacrylate-co-dodecyl methacrylate), was studied by the spin probe method with a nitroxide spin probe, 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO). The influence of changes in the composition of the copolymer (methyl methacrylate-co-dodecyl methacrylate) on the molecular mobility and composition of the IPNs is characterized by changes of the empirical spectral parameters T50G and τR. The molecular mobility was shown to diminish with rising content of methyl methacrylate in the copolymer. © of SCI. 相似文献
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Thanks to their considerable electrochemical and mechanical properties, fiber‐shaped supercapacitors have become the most potential energy storage devices for portable and wearable electronics in the future; however, challenges still exist in the pursuit of practical applications among them. In this work, ternary microfibers, which are composed of TEMPO‐oxidized cellulose nanofibers/reduced graphene oxide microfiber cores coated with polypyrrole shell layers, are successfully fabricated through industrializable and sustainable wet‐spinning and interfacial polymerization strategies. The prepared microfibers possess well‐defined microstructures and outstanding mechanical properties (559 MPa). When assembled into symmetrical all‐solid‐state fiber‐shaped supercapacitors (FSCs), they exhibit remarkable electrochemical properties (647 mF cm?2, 14.37 µWh cm?2 at 0.1 mA cm?2), prominent cycling stability (92.5% capacitance retention and 92.6% coulomb efficiency after 10 000 cycles), and extraordinary flexibility (no significant decay in capacitance after 5000 bending cycles), which are superior to all the congeneric FSCs reported to date. The prominent performances are ascribed to the synergistic effect of the well‐designed ternary system and synergistic effects between interior components. The advantages in electrochemical, mechanical, and industrial properties of the ternary FSCs can provide reference and boost the development of flexible energy storage applications. 相似文献