交替多层TPU／SEBS复合材料阻尼隔声性能的研究

用自行设计的微层挤出体系制备了热塑性聚氨酯弹性体／苯乙烯-乙烯-丁烯-苯乙烯嵌段共聚物（TPU／SEBSS）交替多层复合材料,同时准备了同组分的传统共混样品。实验结果结果表明：与传统共混样品相比,交替多层TPU／SEBS复合材料具有更宽的阻尼温域、更高的隔音系数和更优异的力学性能。并且随着层数的增加,其阻尼、隔声和力学性能提高。     

隔声复合材料隔声性能的数值模拟及实验研究

根据隔声原理,制备了一种内部均布钢球的玻璃纤维增强树脂基隔声复合材料。分别使用数值模拟与实验研究的方法研究了复合材料的隔声效果。模拟数值结果和实验结果均显示了隔声复合材料有良好的隔声性能。针对阻抗管测量隔声方法,利用有限元方法得到了材料隔声量的数值模拟结果。均值材料计算结果与理论结果的比较以及隔声复合材料的计算结果与实验结果的比较,证明了该数值模拟方法在模拟材料隔声量的有效性与可行性。     

改性氧化石墨烯/丁基橡胶复合材料的制备和隔声性能研究

通过Hummers法并以硅烷偶联剂KH-550为改性剂制备改性氧化石墨烯(GO),以改性GO作为补强填料、丁基橡胶(IIR)为橡胶基体制备改性GO/IIR复合材料,并对其性能进行研究。结果表明:加入改性GO制备的复合材料的拉伸强度先增大后减小,损耗因子峰值增大,阻尼温域扩宽,隔声性能略有提升;复合材料可以有效抑制单层镀锌钢板的共振和吻合效应,基于其阻尼特性制备的约束阻尼隔声板隔声性能明显提高。     

汽车隔音垫用聚氨酯软质高回弹泡沫的吸音性能研究

通过驻波管法测试不同隔音垫聚氨酯软质高回弹泡沫的吸声系数,结合显微镜对泡沫的力学特性和形态进行观察和分析。研究结果表明,泡沫在低频区的吸声系数随厚度的增加而提高,而在高频区则有所减弱;泡沫的吸声系数随密度增加而提高;泡孔形态对泡沫的吸声性能有显著影响,细密而均一的泡孔有利于声能的吸收;不同异氰酸酯由于反应性和结构上的差异,泡沫也表现出不同的吸声特性;高压发泡生产的泡沫峰值吸声频率稍向高频区移动,复合乙烯–醋酸乙烯共聚弹性体（EVA）后泡沫的峰值吸声频率稍向低频区移动。     

低密度聚乙烯/氧化锌复合材料制备及其隔声性能研究

采用钛酸酯偶联剂对氧化锌（ZnO）进行表面改性,改性ZnO与低密度聚乙烯（LDPE）制备LDPE/ZnO复合材料。分析ZnO形貌及添加量对复合材料力学性能、阻尼性能、隔声性能及热稳定性的影响。结果表明：改性ZnO与LDPE具有良好的界面相容性,ZnO可以提升LDPE/ZnO复合材料的抗拉强度、隔声性能及热稳定性,四针状氧化锌（T-ZnO）添加量为5%时,复合材料的力学性能最好,综合性能最优。     

填充型NBR/EPDM导电复合材料的研究

研究了石墨/炭黑填充的NBR/EPDM导电复合材料力学性能、动态力学性能和压阻、温阻特性。结果表明,随NBR用量的减少,复合材料拉伸强度、撕裂强度和拉断伸长率均降低;与纯胶相比,填料在NBR/EPDM中分散性变差,复合材料Payne效应和损耗因子都增大。电阻率测试结果表明,NBR/EPDM并用胶电阻率明显低于纯胶;恒温下其电阻率随压力的增大先减小后增大;恒压下其电阻率随温度的升高而减小;NBR/EPDM并用比不同时,复合材料电阻率随压力、温度的变化趋势不尽相同。     

环形局域共振弹性膜结构低频隔声特性分析

针对超低空空投拉平阶段由航空发动机的噪声引起的非线性PIO (驾驶员诱发振荡)的问题,采用环形局域共振膜结构模型进行减振降噪。结合有限元法和仿真实验对环形弹性膜结构带隙生成机理、带隙宽度影响因素及隔声特性进行分析。仿真实验结果显示：带隙是由共振单元与弹性波耦合的结果,耦合强度直接影响共振频率和带隙宽度;带隙宽度和共振频率受薄膜尺寸和表面面密度的影响,即内环半径越大,表面面密度越大,带隙越宽,共振频率越高;隔声量取决于薄膜面密度、圆环面密度及中心质量环的位置。所得结果：通过优化结构参数,使其在低频范围具有良好的隔振效果,有效的抑制振荡,显著改善飞行品质。     

Dual Band Resonance in Tetragonal BaTiO3/NBR Composites for Microwave Absorption Applications

Tetragonal BaTiO₃ bulk samples are prepared using the solid‐state route in conjunction with intermediate high‐temperature annealing steps. The (002) and (200) X‐ray diffraction peaks near 2?~45° and 310, 520, and 720 cm^?1 characteristic vibrational modes in Raman spectroscopic measurements confirm the tetragonal crystallographic structure of BaTIO₃ bulk samples. The 1100°C annealed BaTiO₃ sample showed optimal tetragonality ~1.016 and the same is used for BaTiO₃–acrylonitrile butadiene rubber (NBR) composites at different BaTiO₃ loading fractions in parts per hundred (PHR). These BaTiO₃/NBR composite systems exhibit dual band microwave resonance, widening the operating window for microwave absorption applications. Eighty PHR BaTiO₃/NBR composite exhibits microwave reflection losses (RL) at 9.5 and 16.5 GHz with ~?9 and ~?18 dB reflection losses, respectively. The onset of dual band is attributed to the ferroelectric‐induced dipolar relaxation at 9.5 GHz and its second‐order resonance at 16.5 GHz in such composite systems.     

隔震支座用天然橡胶/丁腈橡胶/受阻酚AO-60复合材料的制备与性能研究

将丁腈橡胶（NBR）/受阻酚AO-60杂化材料与天然橡胶（NR）共混,制备了NR/NBR/AO-60复合材料。利用透射电子显微镜（TEM）、差示扫描量热（DSC）、动态力学分析(DMA)、橡胶加工分析仪（RPA）、力学测试等手段研究了复合材料的微观结构和阻尼性能、物理机械性能。结果表明：复合材料中NR相和NBR/AO-60相之间具有一定的相容性,且当NR/NBR/AO-60比例为50/50/20时,出现了部分双连续相结构。随着NBR/AO-60比例的增加,复合材料在-20℃-40℃温度范围和0-150%应变范围内的损耗性能大幅增加,表现出满足隔震支座需求的高阻尼性能。其中,NR/NBR/AO-60（50/50/20）复合材料具有高阻尼、高强度、高柔性等特性,在橡胶隔震支座领域有很好的应用前景。     

Study of carbon black distribution in BR/NBR blends based on damping properties: Influences of carbon black particle size,filler, and rubber polarity

Effects of filler and rubber polarity on the distribution of filler in butadiene/nitrile rubber (BR/NBR) blends were investigated, using the dynamic mechanical thermal analysis technique. As 30-phr filler is added, the reduction in heights of damping peaks (tan δ_max), attributed to the dilution effect, was observed. It was also found that the BR phase in the blends, compared to the NBR phase, is more preferential for small- and large-particle size carbon blacks to reside, probably because of the lower viscosity and lower polarity of the BR phase. The addition of silica instead of carbon black leads to an increase in filler migration to the NBR in the 20/80 BR/NBR blend, which is attributed to the strong silica–NBR interaction. In addition, an increase in NBR polarity promotes carbon black migration to the BR phase. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3198–3203, 2001     

密闭式炼胶(塑)机转子端面密封技术

主要阐述了密闭式炼胶（塑）机中端面密封装置的相关技术、结构形式及其工作特点,以及动圈的结构特点和加工工艺技术。     

Multiscale designed SiCf/Si3N4 composite for low and high frequency cooperative electromagnetic absorption

With the aim to design a particular material for low and high frequency cooperative electromagnetic absorption at high temperature, a multiscale design is proposed by combining the microstructure and meta‐structure in one material. The SiC_f/Si₃N₄ composite is prepared via the chemical vapor infiltration technique with SiC_f as the EM wave absorbing phase and Si₃N₄ as the wave‐transparent ceramic matrix. The crossing grooved meta‐structure is designed and fabricated to further improve its absorbing properties and to guarantee its absorbing capacity stability at high temperature. A minimum reflection loss of ?15.3 dB and ?14.8 dB can be reached at 8 and 18 GHz with a total thickness of 5 mm. The temperature‐dependent reflection loss of the designed meta‐structure keeps relative reliable high temperature absorbing performances from room temperature to 500°C. This effective enhanced EM wave absorbing property is believed to be a consequence of multiscale effect induced by combining the traditional EM absorbing materials with metamaterial structure.     

Effect of Hindered Phenol AO‐80 on the Damping Properties for Nitrile‐Butadiene Rubber/Phenolic Resin: Molecular Simulation and Experimental Study

A combined study of molecular dynamics (MD) simulation, experimental, and linear regression analysis method is presented for hindered phenol of 3,9‐bis[1,1‐dimethyl‐2‐{b‐(3‐tertbutyl‐4‐hydroxy‐5‐methylphenyl)propionyloxy}ethyl]‐2,4,8,10‐tetraoxaspiro‐[5,5]‐undecane (AO‐80)/nitrile‐butadiene rubber/linear phenolic resin (AO‐80/NBR/PR) composites with different AO‐80 contents to quantitatively establish the relations between microstructure and damping performance. The number of hydrogen bonds (N_HBs), the fractional free volume (FFV), and the binding energy (E_binding) of AO‐80/NBR/PR composites with different AO‐80 content are calculated by MD simulation from the microscopic scale. Damping parameters, including the loss factor peak (tan δ_max) and the loss peak area (TA) (tan δ > 0.3), are obtained by dynamic mechanical analysis from macroscopic scale. The quantitative relationships between microstructure parameters (N_HBs, E_binding, and FFV) and macroscopic damping properties (tan δ_max and TA) are obtained by linear regression analysis. This research is expected to provide a theoretical guidance for improving the damping performance of rubber‐based organic hybrid composites.     

Tailoring electronic properties and kinetics behaviors of Pd/N-CNTs catalysts for selective hydrogenation of acetylene

Pd catalyzed selective hydrogenation of acetylene shows remarkable electronic effects. In this work, a strategy is proposed to tailor the electronic properties of Pd nanoparticles by nitrogen doping of carbon nanotubes (CNT) support toward the improved reaction kinetics. While excluding the Pd size effects, the intrinsic promotional effects of the nitrogen doping are demonstrated, which are mainly due to the increased Pd electron density resultant from the presence of more graphitic nitrogen species based on X-ray photoelectron spectroscopy measurements and density functional theory (DFT) calculations. Kinetics analysis and C₂H₂/C₂H₄-temperature-programmed desorption (TPD) measurements reveal that the electron-rich Pd catalyst with the moderately weakened adsorption strength can give rise to the decreased activation energy and thus the simultaneously enhanced activity, selectivity, and stability. The aspects demonstrated here could guide the rational design and optimization of Pd catalysts for the selective hydrogenation of acetylene.     

Fabrication and Dielectric,Mechanical, and Thermal Properties of Low-Density Polyethylene (LDPE) Composites Containing Surface-Passivated Silicon (Si/SiO2 Core/Shell Nanoparticles)

Composites of low-density polyethylene containing between 1 and 5?wt% of Si/SiO₂ core/shell nanoparticles were prepared by ball milling method. The thermal, mechanical, and dielectric properties of composites were investigated in terms of composition, frequency, and temperature. The results showed that the dielectric permittivity increased smoothly with a rise of Si/SiO₂ particle. The dielectric permittivity and loss decreases and increases with temperature, respectively. The resistance of composites to erosion due to partial discharge was significantly improved by adding nanoparticles. The results have demonstrated that ball milling was an effective method for producing relatively homogeneous nanocomposite up to 4?wt% Si/SiO₂.     

Preparation,Characterization, and Dielectric Properties of PP/CaTiO3 Composites for Microwave Substrate Applications

Calcium titanate (CaTiO₃) filled polypropylene (PP) composites have been fabricated through compression molding method. The phase purity of the PP/CaTiO₃ composites was studied using X‐ray diffraction studies. Scanning electron microscopy technique has been employed to study the dispersion of the particulate filler in the PP matrix. The dielectric constant and loss tangent of the composites were measured at X‐band frequency region using waveguide cavity perturbation technique. PP/CaTiO₃ composite has an effective dielectric constant of 11.74 and loss tangent 0.007 at optimum filler loading. The experimental dielectric constant of filled composites was compared with theoretically predicted dielectric constant values obtained using different modeling approaches. The linear coefficient of thermal expansion of PP/CaTiO₃ composites was studied using thermomechanical analyzer.     

Highly conductive and flexible bilayered MXene/cellulose paper sheet for efficient electromagnetic interference shielding applications

In this work, a robust and flexible bilayered MXene/cellulose paper sheet with superhigh electrical conductivity was prepared via vacuum-assisted filtration and a subsequent hot-pressing process for electromagnetic interference (EMI) shielding applications. By tightly assembling few-layered MXene (f-Ti₃C₂T_x) on the cellulose substrate via hydrogen bonds, an effective and interconnected conductive network was constructed in the paper sheet, resulting in a high electrical conductivity of 774.6–5935.4 S m^?1 at various f-Ti₃C₂T_x loadings. The highly conductive MXene layer can promptly reflect a great amount of incident EM waves, a process which preceded the transmission of EM waves in the cellulose matrix. Owing to the highly efficient reflection-dominated EMI shielding mechanism, the resultant bilayered MXene/cellulose paper sheets exhibit excellent EMI shielding effectiveness of 34.9–60.1 dB and specific EMI shielding efficiency of 290.6–600.7 dB mm^?1. Moreover, the MXene/cellulose paper sheets demonstrated improved mechanical strength (up to 25.7 MPa) and flexibility due to the mechanical frame effect acted by the cellulose substrate. Consequently, the robust and flexible bilayered MXene/cellulose paper sheet is a promising candidate for application in next-generation electric devices.     

Novel Comb-Like Copolymer Dispersant for Polypropylene/CaCO3 Composites and Its Influence on Dispersion,Crystallization, Mechanical,and Thermal Properties

A novel comb-like copolymer with carboxyl group as an anchoring group and polycaprolactone as a solvent chain was first used as the dispersant of CaCO₃ particles in polypropylene (PP). The dispersion of CaCO₃ particles in PP matrix was significantly improved in the presence of comb-like copolymer dispersant because of the strong repulsive force caused by steric hindrance effect. The influences of the coating amount of comb-like copolymer dispersant on crystallization behaviors, mechanical properties, and thermal stabilities were systematically investigated. The crystallization temperature, crystallinity, and crystallization rate of PP/CaCO₃ composites prepared with monolayer-coated CaCO₃ were all improved, where the monolayer comb-like copolymer coating remained as a rigid layer and provided a noticeable nucleating effect. The PP/CaCO₃ composites coated with monolayer SP comb-like copolymer also had the best mechanical properties, including tensile strength, Young’s modulus, flexural modulus, and impact strength because of the good dispersion of CaCO₃ particles in PP matrix. The thermal stability of PP/CaCO₃ composites were measured by thermogravimetric analysis. The results showed that SP comb-like copolymer dispersant treated CaCO₃ filled composites had excellent thermal stability than untreated and neat PP, especially for the composite prepared with monolayer-coated CaCO₃.