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81.
82.
83.
极低密度聚乙烯与其它聚乙烯的共混 总被引:3,自引:0,他引:3
从结构角度,用DSC,WAXD,SAXS研究了聚乙烯(PE)家族中极低密度聚乙烯(VLDPE)与其它PE的互容性.HDPE/VLDPE是共晶互容的,以其大量无规部分“溶解”了HDPE的结晶缺陷部分,提高了HDPE的Tc,Tm,Xc,结晶峰半高宽变窄,晶胞参数随组成而有最低值.VLDPE与LLDPE结构极为相似,DSC及WAXD证明其共混物是共晶相容体系.LDPE/VLDPE的结晶度符合按组成的计算值,但晶胞参数a,b以及晶粒尺寸增大,DSC上有分别相应于两组份的两个Tm;VLDPE的Tc,Tm峰高之和高于按组份的计算值,LDPE的Tm,Tc则低于计算值.认为是正如LLDPE/LDPE,LDPE向充满整个体积的VLDPE中不断填入,以VLDPE为晶核而结晶,形成相分离的不相容体系. 相似文献
84.
M. D'Apuzzo A. Aronne S. Esposito P. Pernice 《Journal of Sol-Gel Science and Technology》2000,17(3):247-254
The sol-gel synthesis of silicophosphate gels using phosphoryl chloride and tetraethoxysilane as molecular precursors is reported and discussed. Gel-derived glasses and films having the molar compositions 10P2O5 · 90SiO2 and 30P2O5 · 70SiO2 have been obtained. The structure of the dried gels as well as the structural modifications that occurs during the transformations in gel-derived glasses are analyzed by Fourier transform infrared spectroscopy (FTIR). It has been found that the evidence of the P—O—Si linkages begins to appear only on the FTIR spectra of the bulk gels heat treated up to 400°C while they are well resolved on the FTIR spectra of the bulk gel samples heated up to 1000°C indicating that at this temperature the transformation in the corresponding gel-derived glasses occurs. The humidity sensitive properties of the gel-films have been evaluated by electrochemical impedance spectroscopy (EIS). The phosphorous content as well as the temperature of the heat treatments strongly affect the sensitivity to RH of the gel-derived films. 相似文献
85.
Crystalline [Y(OH2)3(NCMe)(benzo-15-crown-5)][ClO4]3·benzo-15-crown-5-CH3CN can be obtained by slowly cooling a reaction mixture of Y(ClO4)3·n H2O with benzo-15-crown-5 in a solution of acetonitrile and methanol (3 : 1) from 60°C to room temperature. The crystal structure of this complex has been determined at –150 and 20°C. The complex is triclinic,P
. At –150°C the cell parameters area = 11.986(4),b = 12.071(7),c = 16.364(5) Å, = 93.56(3), = 98.68(3), = 109.68(4)°, vol = 2187 Å3, andD
calc = 1.61 g cm–3 forZ = 2 formula units. 3633 independently observed [F
o 5(F
o)] reflections were used in the final least-squares refinement leading to an agreement index ofR = 0.048. The Y(III) ion coordination geometry approximates a tricapped trigonal prism with three water molecules and three benzo-15-crown-5 oxygen atoms forming the prism, with the two remaining benzo-15-crown-5 oxygen atoms and the acetonitrile molecule completing the coordination as capping atoms. The three water molecules hydrogen bond a second crown ether molecule and two of the perchlorate anions. The two acetonitrile molecules have contacts with perchlorate oxygen atoms close enough for some weak interaction. One perchlorate is ordered, one is partially disordered as is the coordinated solvent molecule, and the third anion is totally disordered. The two unique crown ether molecules have distinctively different conformations.For Part 20, see reference [1]. 相似文献
86.
Jeong Hyun Yeum Byung Chul Ji Chul Joo Lee Ji Youl Lee Sang‐Seob Lee Sam Soo Kim Joon Ho Kim Won Seok Lyoo 《Journal of polymer science. Part A, Polymer chemistry》2002,40(8):1103-1111
To prepare water‐soluble, syndiotacticity‐rich poly(vinyl alcohol) (PVA) microfibrils for various industrial applications, we synthesized syndiotacticity‐rich, low molecular weight PVA by the solution polymerization of vinyl pivalate (VPi) in tetrahydrofuran (THF) at low temperatures with 2,2′‐azobis(2,4‐dimethylvaleronitrile) (ADMVN) as an initiator and successive saponification of poly(vinyl pivalate) (PVPi). Effects of the initiator and monomer concentrations and the polymerization temperature were investigated in terms of the polymerization behaviors and molecular structures of PVPi and the corresponding syndiotacticity‐rich PVA. The polymerization rate of VPi in THF was proportional to the 0.91 power of the ADMVN concentration, indicating the heterogeneous nature of THF polymerization. The low‐temperature solution polymerization of VPi in THF with ADMVN proved to be successful in obtaining water‐soluble PVA with a number‐average degree of polymerization (Pn) of 300–900, a syndiotactic dyad content of 60–63%, and an ultimate conversion of VPi into PVPi of over 75%. Despite the low molecular weight of PVA with Pn = 800, water‐soluble PVA microfibrillar fibers were prepared because of the high level of syndiotacticity. In contrast, for PVA with Pn = 330, shapeless and globular morphologies were observed, indicating that molecular weight has an important role in the in situ fibrillation of syndiotacticity‐rich PVA. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1103–1111, 2002 相似文献
87.
Xingxing Lu Huan Xu Xiaoming Zhang Tengda Sun Yufan Lin Yongheng Zhang Honghong Li Xuesheng Li Xinling Yang Hongxia Duan Yun Ling 《Molecules (Basel, Switzerland)》2022,27(18)
Neonicotinoids are important insecticides for controlling aphids in agriculture. Growing research suggested that neonicotinoid insecticides are a key factor causing the decline of global pollinator insects, such as bees. Flupyrimin (FLP) is a novel nicotinic insecticide with unique biological properties and no cross-resistance, and is safe for pollinators. Using FLP as the lead compound, a series of novel compounds were designed and synthesized by replacing the amide fragment with a sulfonamideone. Their structures were confirmed by 1H NMR, 13C NMR and HRMS spectra. Bioassay results showed that compound 2j had good insecticidal activity against Aphis glycines with an LC50 value of 20.93 mg/L. Meanwhile, compound 2j showed significantly lower acute oral and contact toxicity to Apis mellifera. In addition, compound 2j interacted well with the protein in insect acetylcholine binding protein (AChBP). The molecular docking on honeybee nicotinic acetylcholine receptor (nAChR) indicated that the sulfonamide group of compound 2j did not form a hydrogen bond with Arg173 of the β subunit, which conforms to the reported low bee-toxicity conformation. In general, target compound 2j can be regarded as a bee-friendly insecticide candidate. 相似文献
88.
Hao Zhang Lili Liang Hailing Xi Datong Liu Zhanguo Li Xiaoyan Lin 《Molecules (Basel, Switzerland)》2022,27(19)
Compared with polymers and nanoparticles, fatty alcohols can not only increase the stability of foam, but also maintain better foamability at pH < 2, which is beneficial to reduce waste liquid and increase decontamination efficiency for radioactive surface pollution. However, different fatty alcohols have different hydrophobic chain lengths. The effects of fatty alcohols with different chain lengths on the performance of decontamination foam were studied at pH < 2, to assist in the selection of suitable fatty alcohols as foam stabilizers. Combined with betaine surfactant and phytic acid, biomass-based foams were synthesized using fatty alcohols with different chain lengths. When the hydrophobic tail groups of the fatty alcohol and the surfactant were the same, the foam showed the best performance, including the lowest surface tension, the highest liquid film strength, the greatest sag-resistance and the best stability. However, when the hydrophobic tail groups were different, the space between adjacent surface active molecules was increased by thermal motion of the excess terminal tail segments (a tail-wagging effect), and the adsorption density reduced on the gas-liquid interface, leading to increased surface tension and decreased liquid film strength, sag-resistance and stability. The use of decontamination foam stabilized by fatty alcohols with the same hydrophobic group as the surfactant was found to increase the decontamination rate of radioactive uranium pollution from 64 to over 90% on a vertical surface. 相似文献
89.
90.
:根据Stevenson等效电路法设计了两个X波段低副瓣波导缝隙阵列天线。通过建立多个缝隙时的谐振长度提取模型,计算了存在缝隙间互耦时的谐振长度。两个阵列天线测试结果和仿真结果吻合良好,线阵中心频率实测增益为17.83 dB,其仿真结果为18.2 dB,实测副瓣为-28.12 dB,其仿真结果为-29.97 dB;平面阵列中心频率实测增益为27 dB,其仿真结果为27.9 dB, 实测H面副瓣为-27.2 dB,其仿真结果为-29.9 dB,实测E面副瓣为-22 dB,其仿真结果为-22 dB。 相似文献