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通过在同向双螺杆挤出机中进行实验,考察了E—SBR/白炭黑/硅烷基橡胶/填料复合材料(RFC)的连续混炼。在混炼区段捏合块类型变化(正向捏合块、中性捏合块和反向捏合块)情况下,研究了三种不同的螺杆构型。针对这三种不同的螺杆构型对混炼效率进行了比较。研究了胶料性能(如填料-填料相互作用、门尼黏度)以及硫化胶的机械性能,发现通过采用带反向捏合块的螺杆构型,白炭黑粒子的分散度高于带正向捏合块和中性捏合块者;利用反向捏合块所获得的胶料性能和硫化胶性能,与在密炼机内混炼的对照胶料的性能大致相当。 相似文献
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啮合型同向旋转双螺杆挤出机的螺杆特性及其应用 总被引:1,自引:0,他引:1
介绍了啮合型同向旋转双螺杆挤出机的起源和发展,着重论述了该型挤出机挤压系统中的螺杆型式、螺纹元件和捏合元件的输送及混炼特性、螺杆组合型式和操作条件以及应用情况。 相似文献
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介绍了啮合型同向旋转双螺杆挤出机的起源和发展,着重论述了该型挤出机挤压系统中的螺杆型式、螺纹元件和捏合元件的输送及混炼特性、螺杆组合型式和操作条件以及应用情况。 相似文献
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同向双螺杆挤出过程不同螺杆构型的混合性能分析 总被引:2,自引:0,他引:2
利用POLYFLOW有限元分析软件列同向双螺杆挤出过程不同螺杆组合的流道进行了三维等温非牛顿流场模拟,通过计算结果后处理,分析了全正向螺纹流道、全正向捏合盘流道、全反向捏合盘流道等6种不同螺杆构型的分布混合性能和分散混合性能。 相似文献
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啮合同向双螺杆挤出过程聚合物粒料熔融机理研究(二):正向捏合块组?… 总被引:5,自引:3,他引:2
以装有玻璃视窗的可视化双螺杆挤出机为手段,在不同操作条件下对高密度聚乙烯(HDPE)粒料在不同正向捏合块(即由正向捏合盘所组成的螺杆区段)中的熔融过程进行了实验研究。以实验现象为基础,提出了双螺杆挤出过程中海-岛式熔融模型的概念。研究表明,耗散-混合熔融是捏合块中聚合物熔融的典型形态;螺杆构型、螺杆转速、加料量是决定聚合物颗粒熔融的主要因素。 相似文献
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应用全析因设计方法,研究了捏合块角度、比产率(喂料速率/螺杆转速)和螺杆转速对双螺杆挤出机机筒不同位置的延迟时间和平均停留时间的影响,考察了各因素之间的交互作用。结果表明,在所选取的操作条件下,螺杆转速对延迟时间和平均停留时间的影响最大,捏合块角度与比产率的影响程度相近。3因素两两交互作用对延迟时间的影响程度由大到小依次为捏合块角度与比产率、螺杆转速与比产率、捏合块角度与螺杆转速;对平均停留时间的影响由大到小依次为比产率与螺杆转速、捏合块角度与比产率、捏合块角度与螺杆转速。3因素3阶交互作用对平均停留时间的影响比较显著。 相似文献
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研究了用行星式螺杆挤出机连续混炼的白炭黑填充胶料。研究用的原材料为乳聚SBR/白炭黑/硅烷/填料复合胶料,填料与硅烷在复合胶料的制备过程中充分反应,生成了完全硅烷化的白炭黑。由于行星式螺杆挤出机具有极强的冷却能力,所以,所有胶料组分,包括交联剂都可在同一个喂料段计量加入。未发现混炼胶有焦烧现象,连续混炼胶料的性能(如,填料分散和交联性能)以及硫化胶性能(如,拉伸强度和硬度)都与用密炼机混炼的胶料相当。连续混炼的能耗仅为密炼机混炼的1/3。 相似文献
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R. K. DATTA 《Journal of the American Ceramic Society》1971,54(5):262-265
High-temperature X-ray diffraction and differential thermal analyses showed that LiGa5 O8 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 LiGa5 O8 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 MgGa2 O4 is present. The subsolidus equilibrium relations in the system MgGa2 O4 -LiGa5 O8 are discussed. 相似文献
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Ahmed A. Ghani Ali I. Eatah El-Mozamel El-Faramawy 《Journal of the American Ceramic Society》1988,71(12):492-C
Magnetoresistance measurements (Δ/R) were carried out on Cu x Co1- x Fe2 O4 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 μD 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. 相似文献
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Sintering kinetics of the system Si3 N4-Y2O3 -Al2 O3 were determined from measurements of the linear shrinkage of pressed disks sintered isothermally at 1500° to 1700°C. Amorphous and crystalline Si3 N4 were studied with additions of 4 to 17 wt% Y2 O3 and 4 wt% A12 O3 . 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 ' -Si3 N4 and glass or β '-Si3 N4 , α '-Si3 N4 , and glass. The compositions and amounts of the residual glassy phases are estimated. 相似文献
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The effects of temperature and restraint upon the hydration and the expansion of 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 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. 相似文献
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Steven A. Markgraf Shiv K. Sharma Amar S. Bhalla 《Journal of the American Ceramic Society》1992,75(9):2630-2632
Raman spectra are reported for fresnoite (Ba2 Ti(Si,Ge)2 O8 glasses, and comparison is made between the Raman spectra of the corresponding crystalline powders and glasses of Ba2 TiSi2 O8 and Ba2 TiGe2 O8 . The Ba2 TiGe2 O8 glass spectra show correspondence with the Ba2 TiGe2 O8 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 Ba2 TiGe2 O8 glass as revealed by a strong band at 824 cm−1 in the I glass spectrum. The Ba2 TiSi2 O8 glass spectra are similar to the Ba2 TiSi2 O8 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 Ba2 TiSi2 O8 glass has a structure similar to the crystalline phase. 相似文献
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A new ampholytic homopolypeptide, , 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 () 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. 相似文献
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A study of CO hydrogenation over and 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 H2O2 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 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 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 and , for dispersions between 10 and 20%. On the other hand, the methane turnover frequency is independent of Pd dispersion over , but increases with decreasing dispersion over . It is further observed that the Pd morphology influences the specific activity of for methanol synthesis: Pd(100) is nearly threefold more active than Pd(111). For a fixed morphology, the specific methanol synthesis activity of is a factor of 7.5 greater than that of . 相似文献
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Raman spectra of sulfided catalysts were obtained using in situ techniques for two sulfiding methods. For samples sulfided by 10% at 400 °C, MoS2 structures were observed. A stepwise sulfiding using 10% , 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 MoS 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. 相似文献
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Silvia Schicker Daniel E. García Igor Gorlov Rolf Janssen Nils Claussen 《Journal of the American Ceramic Society》1999,82(10):2607-2612
Wet milling of Al2 O3 -aluminide alloy (3A) precursor powders in acetone has been investigated by milling Fe/Al/Al2 O3 and Fe2 O3 /Al/Al2 O3 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 Fe2 O3 /Al/Al2 O3 powder mixtures were observed, the formation of a nanocrystalline, ordered intermetallic FeAl phase in Fe/Al/Al2 O3 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. 相似文献