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111.
Variation of anions in layered double hydroxides: Effects on dispersion and fire properties 总被引:1,自引:0,他引:1
Layered double hydroxides (LDHs) are interesting materials for nanocomposite formation because one can vary the identity of the metals, the anions and the stoichiometry to see the effect of these on the ability of the nano-material to disperse in a polymer and to see what effect dispersion has on the properties of the polymer. In this study, the anions 2-ethylhexyl sulfate (SEHS), bis(2-ethylhexyl) phosphate (HDEHP) and dodecyl benzenesulfonate (SDBS) have been utilized as the charge balancing anions to synthesize organo-LDHs. Nanocomposites of poly(methyl methacrylate) (PMMA) and polystyrene (PS) with organo-LDHs were prepared both by melt blending and bulk polymerization. X-ray diffraction and transmission electron microscopy were used to characterize the morphology of the nanocomposites while the thermal stability and fire properties of nanocomposites were studied by thermogravimetric analysis and cone calorimetry; the mechanical properties are also investigated. In general, it is easier to disperse these organo-LDHs in PMMA than in PS, but the sulfate cannot be dispersed at the nanometer level in either material. The addition of these organo-LDHs does not affect the mechanical properties. The best fire properties are obtained with the sulfonate LDH, SDBS; the reduction in the peak heat release rate is almost 50% for both polymers. 相似文献
112.
生物可降解聚丁二酸/甲基丁二酸丁二酯系列共聚物的合成和表征 总被引:3,自引:0,他引:3
摘要合成了一系列聚丁二酸/甲基丁二酸丁二醇共聚酯(PBSM), 利用DSC, 1H NMR和X射线衍射等方法对共聚物组成、 热学性能、 结晶性能、 等温结晶行为进行了研究. 结果表明, 引入甲基丁二酸共聚单元较为显著地改变了聚丁二酸丁二酯(PBS)的热学性能, 利用Hoffman\|Weeks方程得到的共聚物平衡熔点随共聚物的组分含量增加而降低, 玻璃化转变温度亦有所降低, 熔点则符合无规共聚物的Flory方程. 此外, 利用Avrami方程分别研究了均聚物PBS及共聚物PBSM-20的等温结晶行为, 结果表明, 在所研究的温度范围内, 聚酯结晶速率随温度升高而降低, PBS和PBSM\-20的Avrami指数分别介于2.8~3.0和2.7~3.0之间, 结晶方式为三维生长异相成核, 而X射线衍射测试结果表明晶体结构几乎不变. 相似文献
113.
Ponnaboina Thirupathi 《Tetrahedron》2011,67(38):7301-7310
Tris(pentafluorophenyl)borane [B(C6F5)3] has found to be an efficient catalyst for Friedel-Crafts reactions between activated arenes or heteroarenes and α-amidosulfones. The products undergo further Friedel-Crafts reactions with activated heteroarenes leading to the synthesis of unsymmetrical triarylmethanes. The present synthetic method displayed significant advantages such as low catalyst loading, mild reaction conditions, highly regioselective, high yield, and broad applicability to various substrates. 相似文献
114.
An efficient synthetic method has been developed for the synthesis of 2-arylacrylic esters from the corresponding aryl methyl ketones via Wittig reaction and singlet oxygen ene reaction. Wittig reaction to aryl methyl ketones with (methoxymethyl)triphenylphosphonium chloride in basic condition afforded the methyl enol ethers, and then 2-arylacrylic esters were obtained by singlet oxygen ene reaction, followed by tosylation and elimination in one-pot to the methyl enol ethers in good yields. 相似文献
115.
甲醇是重要的基础化工原料,随着全球甲醇产能过剩,将甲醇催化转化为高附加值的甲醇下游化学品具有重要意义,其中甲醇一步催化转化为甲缩醛(DMM)和甲酸甲酯(MF)等高附加值甲醇下游化学品备受人们的关注,而这一过程中的双功能催化剂是关键。本文对近几年来甲醇催化转化一步合成甲缩醛和甲酸甲酯的双功能催化剂体系进行了总结和评述,特别是对贵金属催化体系、金属氧化物催化体系、杂多酸催化体系等双功能催化剂的催化作用和产物分布特点进行了仔细分析,以期对甲醇催化转化一步合成甲缩醛和甲酸甲酯的工艺放大提供一些参考。 相似文献
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119.
Polymer nanoparticles within the range of 2–5 nm with a solid content of more than 13 wt.% and a narrow molecular weight polydispersity (Mw/Mn ∼ 1.1) were for the first time prepared using a micellar nucleation differential microemulsion polymerization system emulsified by sodium dodecyl sulfate (SDS), with SDS/monomer (methyl methacrylate) and SDS/H2O weight ratios of up to 1:16 and 1:100, respectively. It was found that for benzoyl peroxide (BPO), micellar nucleation is more favorable for the synthesis of smaller polymer nanoparticles than ammonium persulfate (APS) which gives rise to homogeneous nucleation and 2,2′-azobisisobutyronitrile (AIBN) which involves partially heterogeneous nucleation. In the polymerization process, there exists a critical stability concentration (CSC) of SDS, above which the size of the nanoparticles is to be minimized and stabilized. With an increase in the monomer addition rate, the polymerization system changes from a microemulsion system to an emulsion system. A mechanism was proposed to describe the micellar nucleation process of differential microemulsion polymerization. This study may contribute to the development of fine polymer nanoparticles for drug delivery systems. 相似文献
120.
基于HAc-NaAc缓冲体系中,反应温度为25℃时,苯酚阻抑高碘酸钾氧化甲基紫的褪色反应,建立了测定苯酚的阻抑褪色光度新方法.该方法最大吸收波长为580 nm,线性范围为0.02μg/mL~2·2μg/mL,检出限为3.8×10<'-3>μg/mL,方法用于环境水中苯酚的测定,相对标准偏差为1.97%~2.25%,回收... 相似文献