丙烯酸酯橡胶/液体氟橡胶并用胶性能的研究

研究液体氟橡胶用量对丙烯酸酯橡胶(ACM)/液体氟橡胶并用胶性能的影响。结果表明:加入液体氟橡胶,并用胶的t_(10)延长,t_(90)缩短,F_L和F_(max)减小,加工性能提升;ACM与液体氟橡胶相容性良好,并用胶的耐寒性能有所下降;随着液体氟橡胶用量的增大,并用胶的物理性能、热空气老化性能、热稳定性能和耐油性能先提高后降低,压缩永久变形增幅增大;当液体氟橡胶用量为5份时,并用胶的综合性能较佳。     

纳米凹凸棒土/炭黑复合填料对天然橡胶/丁苯橡胶/顺丁橡胶并用胶性能的影响

研究纳米凹凸棒土/炭黑N770/炭黑N330复合填料中纳米凹凸棒土/炭黑N770用量比对天然橡胶(NR)/丁苯橡胶(SBR)/顺丁橡胶(BR)并用胶性能的影响。结果表明:采用纳米凹凸棒土/炭黑N770/炭黑N330复合填料时,随着凹凸棒土用量增大,并用胶的F_L和F_(max)增大,硫化速度减慢,物理性能、耐磨性能和耐屈挠性能提高;纳米凹凸棒土/炭黑N770用量比为30/15时,并用胶的综合性能较优异。与添加其他无机填料(陶土、轻质碳酸钙和白炭黑)/炭黑复合填料的并用胶相比,添加纳米凹凸棒土/炭黑复合填料的并用胶拉伸强度和撕裂强度较高,耐屈挠性能较好,耐磨性能稍差。     

核桃壳粉/丁苯橡胶复合材料的制备与性能研究

采用核桃壳粉(WSP)和丁苯橡胶(SBR)制备WSP/SBR复合材料,研究WSP和偶联剂Si69对复合材料硫化特性、物理性能和动态性能的影响。结果表明,添加未改性的WSP,混炼胶的F_(max)-F_L总体减小,复合材料的物理性能降低,抗湿滑性能提高;经偶联剂Si69改性后,混炼胶的硫化时间延长,交联密度增大,复合材料的拉伸强度提高,耐磨性能改善,压缩疲劳温升降低,胶料的抗湿滑性能提高,滚动阻力降低。     

天然橡胶/顺丁橡胶并用胶在汽车发动机悬置材料中的应用

模拟天然橡胶(NR)/顺丁橡胶(BR)并用胶作汽车发动机悬置材料在使用过程中的受力状态,研究NR/BR并用胶的物理性能和阻尼性能。结果表明:随着BR用量增大,NR/BR并用胶的t_(10)和t_(90)延长,F_(max)增大,强伸性能降低,压缩疲劳温升提高,老化后拉伸强度和拉断伸长率降幅增大;NR/BR并用可以避免NR在低温下阻尼过高问题;为避免NR/BR并用胶压缩疲劳温升加剧,NR/BR并用比不宜大于70/30。     

混炼外场条件对溶聚丁苯橡胶/天然橡胶胶料性能的影响

研究混炼外场条件对溶聚丁苯橡胶/天然橡胶胶料性能的影响。结果表明:随着转子转速增大,混炼胶的门尼粘度变化不大,FL先增大后减小,F_(max)增大,t_(10)缩短,t_(90)变化不大;硫化胶的邵尔A型硬度、拉伸强度和拉断伸长率增大,撕裂强度减小;胶料的Payne效应先增强后减弱。随着初始混炼温度升高,混炼胶的门尼粘度、FL和F_(max)增大,t_(10)和t_(90)缩短;硫化胶的300%定伸应力、拉伸强度、拉断伸长率和撕裂强度呈减小趋势;胶料的Payne效应明显增强。     

硫化温度和时间对胎面胶性能的影响

研究了硫化温度和时间对胎面胶硫化特性、物理性能、耐磨性能和压缩温升的影响。结果表明,随着硫化温度降低和时间延长,F_(max)、F_(max)-F_L和定伸应力整体上呈增大趋势,拉伸强度和撕裂强度先增大到一个极值后减小;耐磨性能逐步提高;压缩温升从135℃开始逐步降低,生热性能提高。     

原位聚合改性EPDM/NR并用胶的性能研究

通过原位聚合法对EPDM进行改性,并研究单体种类和用量对EPDM/NR并用胶物理性能的影响.结果表明,当甲基丙烯酸甲酯(MMA)单体用量(以EPDM质量为5 g计)为10 mL时,并用胶的撕裂强度和拉断伸长率达到最大值;当MMA用量增大到20mL时,并用胶的拉伸强度和邵尔A型硬度分别为9.66 MPa和90度,但拉断伸长率和撕裂强度明显下降.加入苯乙烯单体的EPDM/NR并用胶物理性能下降.     

排胶温度对全钢载重子午线轮胎胎面胶性能的影响

试验研究排胶温度对全钢载重子午线轮胎胎面胶性能的影响。结果表明:混炼胶的排胶温度升高后,胶料的F_L和F_(max)减小,t_(s2)和t_(10)延长,t_(90)略有延长,总体来说对胶料的硫化特性影响不大;硫化胶的邵尔A型硬度、定伸应力和撕裂强度明显提高,阿克隆磨耗量显著减小,压缩生热略有上升,拉断伸长率降低,综合物理性能提高。     

原位反应生成的甲基丙烯酸镁对混炼型聚氨酯补强的研究

在混炼型聚氨酯(MPU)(过氧化物作硫化剂)混炼过程中,氧化镁(MgO)与甲基丙烯酸(MAA)原位反应生成甲基丙烯酸镁(MDMA),研究其对MPU的补强作用。结果表明:当MDMA理论生成量为30份时,随着MgO/MAA物质的量比的增大,MPU硫化胶的拉伸强度先增大后减小,当MgO/MAA物质的量比为0. 6时,拉伸强度达到最大值,综合物理性能最佳;当MgO/MAA物质的量比为0. 6时,随着MDMA理论生成量的增大,混炼胶的F_(max)-F_L显著提高,MPU硫化胶的拉伸强度先增大后减小,玻璃化温度向低温移动,耐低温性能提高,在MDMA用量为30份时,拉伸强度达到最大值,填料网络结构较稳固。     

偶联剂Si69改性白炭黑对NR/SSBR并用胶性能的影响

试验研究偶联剂Si69用量和白炭黑改性方法对白炭黑填充NR/SSBR并用胶性能的影响.结果表明,当采用直接加入法改性白炭黑时,随着偶联剂Si69用量的增大,Payne效应减弱,NR/SSBR并用胶的t10延长,t90缩短,硫化胶的物理性能提高,偶联剂Si69用量以4 5份为宜.与直接加入法改性白炭黑填充并用胶相比,预处理法改性白炭黑填充并用胶的Payne效应减弱,拉伸强度和撕裂强度增大;高温静置处理法改性白炭黑填充并用胶的定伸应力、拉伸强度和损耗模量增大.     

Polymorphism of LiGa5O8 and of LiGa5O8-MgGa2O4Solid Solutions

High-temperature X-ray diffraction and differential thermal analyses showed that LiGa₅O₈ exists in two polymorphs related by the first-order transition at 1138°±3°C of the low-temperature simple-cubic form, space group (probably) O⁷, to the high-temperature spinel (fcc) form, space group O _h ⁷. The transition is rapid, and the high-temperature form in pure LiGa₅O₈ could not be quenched to room temperature under the conditions used. However, the high-temperature polymorph can be quenched under equilibrium conditions when 40 mol% or more MgGa₂O₄ is present. The subsolidus equilibrium relations in the system MgGa₂O₄-LiGa₅O₈ are discussed.     

Magnetoresistance of CuxCo1-xFe2O4 Ferrites

Magnetoresistance measurements (Δ/R) were carried out on Cu _x Co_{1- x} Fe₂O₄ samples with x =1, 0.75, 0.50, 0.25 and cobalt ferrite in the range of magnetic intensity (H) from 1.0 to 4.5 kG. Linear plots were obtained between log (Δ/R) and log H for all compositions except that of cobalt ferrite. The values of n at x =0.5 do not agree with the results of some authors. The discrepancy may be attributed to the value of magnetic field intensity at which such measurements were carried out. The similarity of features of n and μ_D with composition leads us to believe that the magnetoresistance may arise from the scattering of conduction electrons by localized electrons involving the s-d exchange interaction.     

Sintering of Si3N4-Y2O3-Al2O3

Sintering kinetics of the system Si₃N4-Y2O₃-Al₂O3 were determined from measurements of the linear shrinkage of pressed disks sintered isothermally at 1500° to 1700°C. Amorphous and crystalline Si₃N₄ were studied with additions of 4 to 17 wt% Y₂O₃ and 4 wt% A1₂O₃. Sintering occurs by a liquid-phase mechanism in which the kinetics exhibit the three stages predicted by Kingery's model. However, the rates during the second stage of the process are higher for all compositions than predicted by the model. X-ray data show the presence of several transient phases which, with sufficient heating, disappear leaving mixtures of β ' -Si₃N₄ and glass or β '-Si₃N₄, α '-Si₃N₄, and glass. The compositions and amounts of the residual glassy phases are estimated.     

Expansive properties of the mixture C4ASH12 − 2CS III. Effects of temperature and restraint

The effects of temperature and restraint upon the hydration and the expansion of $\text{C}{}_4\text{A}\text{S}\text{H}{}_{12}\text{? 2}\text{C}\text{S}$ mixture compacts in different contact solutions have been investigated. Temperatures above 20°C do apparently hinder the formation of an impervious felt-like layer of ettringite around the $\text{C}{}_4\text{A}\text{S}\text{H}{}_{12}$ particles, thus greatly reducing the retarding effect of the lime. An uniaxial restraint of 1 Kg/cm² is enough to reduce sensibly the expansions which remain however high (about 100%). The results can be satisfactorily interpreted by the reaction and expansion mechanism hypothesized in our previous papers.     

Raman Study of Glasses of Ba2TiSi2O8 and Ba2TiGe2O8

Raman spectra are reported for fresnoite (Ba₂Ti(Si,Ge)₂O₈ glasses, and comparison is made between the Raman spectra of the corresponding crystalline powders and glasses of Ba₂TiSi₂O₈ and Ba₂TiGe₂O₈. The Ba₂TiGe₂O₈ glass spectra show correspondence with the Ba₂TiGe₂O₈ crystalline Raman spectra; the v _s(Ge–O–Ge) mode occurs at 518 cm⁻¹ in the glass and at 521 cm⁻¹ in the crystalline material. Five-fold coordinated titanium is the majority species present in the Ba₂TiGe₂O₈ glass as revealed by a strong band at 824 cm⁻¹ in the I glass spectrum. The Ba₂TiSi₂O₈ glass spectra are similar to the Ba₂TiSi₂O₈ crystalline spectrum; the strongest band is found at 836 cm⁻¹ in the I glass spectrum. Through comparison with the previous Raman data of other titania silicate glasses, we conclude that the Ba₂TiSi₂O₈ glass has a structure similar to the crystalline phase.     

Preparation and properties of poly(Nε,Nε-dicarboxymethyl-l-lysine)

A new ampholytic homopolypeptide, $\text{poly}\text{(N}{}^{\mathrm{\epsilon }}\text{,N}{}^{\mathrm{\epsilon }}\text{-}\text{dicarboxy-methyl-}\text{l}\text{-lysine}\text{)}$, which has one tertiary amino and two carboxyl groups in the side chain has been derived from a hydrochloride salt of poly(L-lysine). The polymer in aqueous solution seems to be in the coil form with locally extended structure (LES) at neutral pH. In both the acidic and alkaline regions, the molar ellipticity of the polymer changes as a result of change in net charge on the side chain. The conformational changes may be from the coil with LES to other coiled forms. 5–7 M NaClO₄ and 80% aqueous methanol induce the α-helix in the polymer at neutral pH. Divalent cations, Cu²⁺ and Ca²⁺, do not induce any remarkably ordered structures such as α-helix or β-structure in the polymer in aqueous solution at any pH. Ultraviolet absorption studies show an absorption peak of the polymer-Cu²⁺ complex near 240 nm. Dependence of the peak intensity on pH at various q values ($\text{q =}\text{[}\text{Cu}{}^{\mathrm{2+}}\text{]}\text{[}\text{residue}\text{]}$) indicates the two steps of the complex formation. At q less than 0.64, the formation is described only with the first step. An average coordination number for Cu²⁺ at the first step was calculated to be about 2 by the method of Mandel and Leyte. The association constant of Cu²⁺ with the residue at the step was determined from the absorption data to be far smaller than that for the Cu²⁺-EDTA complex. The second step of the formation occurs in the case of large q but the absorption data for the second step cannot be obtained exactly due to precipitation.     

Effects of metal-support interactions on the hydrogenation of CO over PdSiO2 and PdLa2O3

A study of CO hydrogenation over $\text{Pd}\text{SiO}{}_2$ and $\text{Pd}\text{La}{}_2\text{O}{}_3$ has been carried out for the purpose of identifying the effects of Pd dispersion, Pd morphology, and support composition on the catalytic activity of supported Pd. The specific activity of each catalyst for methanol and methane synthesis was determined from microreactor studies carried out at a fixed set of reaction conditions. Palladium dispersion was measured by H₂O₂ titration, and the morphology of the Pd crystallites, as expressed by the distribution of Pd(100) and Pd(111) planes, was determined from in situ infrared spectra of adsorbed CO. The crystallite morphology of the $\text{Pd}\text{SiO}{}_2$ catalysts is the same, independent of Pd weight loading: 90% of the surface is comprised of Pd(100) planes and 10% of the surface is comprised of Pd(111) planes. By contrast, the crystallite morphology of the $\text{Pd}\text{La}{}_2\text{O}{}_3$ catalysts changes with Pd loading. Primarily Pd(100) planes are exposed at low-weight loadings while Pd(111) planes are exposed at high-weight loadings. The Pd dispersion has little effect on the methanol turnover frequency over both $\text{Pd}\text{SiO}{}_2$ and $\text{Pd}\text{La}{}_2\text{O}{}_3$, for dispersions between 10 and 20%. On the other hand, the methane turnover frequency is independent of Pd dispersion over $\text{Pd}\text{SiO}{}_2$, but increases with decreasing dispersion over $\text{Pd}\text{La}{}_2\text{O}{}_3$. It is further observed that the Pd morphology influences the specific activity of $\text{Pd}\text{La}{}_2\text{O}{}_3$ for methanol synthesis: Pd(100) is nearly threefold more active than Pd(111). For a fixed morphology, the specific methanol synthesis activity of $\text{Pd}\text{La}{}_2\text{O}{}_3$ is a factor of 7.5 greater than that of $\text{Pd}\text{SiO}{}_2$.     

Wet Milling of Fe/Al/Al2O3 and Fe2O3/Al/Al2O3 Powder Mixtures

Wet milling of Al₂O₃-aluminide alloy (3A) precursor powders in acetone has been investigated by milling Fe/Al/Al₂O₃ and Fe₂O₃/Al/Al₂O₃ powder mixtures. The influence of the milling process on the physical and chemical properties of the milled powders has been studied. Particle refinement and homogenization were found not to play a dominant role, whereas plastic deformation of the metal particles leads to the formation of dislocations and a highly disarranged polycrystalline structure. Although no chemical reactions among the powder components in Fe₂O₃/Al/Al₂O₃ powder mixtures were observed, the formation of a nanocrystalline, ordered intermetallic FeAl phase in Fe/Al/Al₂O₃ powder mixtures caused by mechanical alloying was detected. Chemical reactions of Fe and Al particle surfaces with the atmosphere and the milling media lead to the formation of highly porous hydroxides on the particle surfaces. Hence the specific surface area of the powders increases, while the powder density decreases during milling. The fraction of Fe oxidized during milling was determined to be 0.13. The fraction of Al oxidized during milling strongly depends on the metal content of the powder mixture. It ranges between 0.4 and 0.8.     

In situ laser raman spectroscopy of the sulfiding of Moγ-Al2O3 catalysts

Raman spectra of sulfided $\text{Mo}\text{γ-}\text{Al}{}_2\text{O}{}_3$ catalysts were obtained using in situ techniques for two sulfiding methods. For samples sulfided by 10% $\text{H}{}_2\text{S}\text{H}{}_2$ at 400 °C, MoS₂ structures were observed. A stepwise sulfiding using 10% $\text{H}{}_2\text{S}\text{H}{}_2$, with spectra recorded at 150, 250, and 350 °C, resulted in observation of molybdenum oxysulfide, reduced molybdate, and surface “MoS₂” phases. Reexposure of these samples to air led to radical modification of the oxysulfide structures as well as transformation of some sulfide phases. A model incorporating terminal and bridging MoS bonding and anion vacancies is proposed. This model is based on the conversion of isolated and aggregated molybdate and MoO₃ species to oxysulfide and reduced molybdenum phases. Conversion of reduced molybdenum phases to sulfides is observed to be slow.