混炼工艺对NR/SBR/BR/TRR农业轮胎胎面胶性能的影响

研究混炼工艺对天然橡胶(NR)/丁苯橡胶(SBR)/顺丁橡胶(BR)/轮胎再生橡胶(TRR)农业轮胎胎面胶性能的影响。结果表明:胶料混炼适合采用两段混炼工艺,一段混炼为SBR和TRR与部分炭黑混炼,二段混炼为一段混炼胶与NR、BR、剩余炭黑和其他配合剂混炼;随着一段混炼炭黑加入量增大,硫化胶的拉伸强度和撕裂强度呈增大趋势,一段混炼炭黑加入量较大时硫化胶的拉断伸长率较高,耐磨性能较好;一段混炼加入5/6炭黑的混炼工艺硫化胶的炭黑分散性较好,拉伸强度和撕裂强度较大,耐磨性能较好,生热较低,耐热氧老化和耐臭氧老化性能较好。     

NR/SR并用对全钢载重子午线轮胎胎面胶性能的影响

试验研究NR与SR(SBR或/和BR)并用对全钢载重子午线轮胎胎面胶性能的影响.结果表明,与单用NR相比,SR用量不超过20份的NR/SR混炼胶强度略低,硫化胶的硬度、定伸应力、拉伸强度、拉断伸长率、弹性和耐磨性能相近,拉断永久变形较小,压缩温升略高;SR用量超过20份的NR/SR混炼胶强度较低,硫化胶的300%定伸应力和撕裂强度较低,压缩温升较高,耐磨性能较好.NR与不超过30份(最好为20份)的SBR/BR(不超过20份,最好为10份)并用的全钢载重子午线轮胎胎面胶性能较好.     

硫化体系加料方式对天然橡胶/顺丁橡胶并用胶性能的影响

研究硫化体系加料方式对天然橡胶(NR)/顺丁橡胶(BR)并用胶性能的影响。结果表明:NR/BR并用胶的撕裂强度受硫化体系加料方式影响较大,邵尔A型硬度、拉伸强度和拉断伸长率对硫化体系的加料方式容忍度较高;当氧化锌、硬脂酸和硫黄全部加入BR相中时,NR/BR并用胶的耐磨性能好且大应变下的动态损耗低,综合性能较好。     

炭黑分布对天然橡胶/顺丁橡胶并用胶性能的影响

研究炭黑在天然橡胶(NR)/顺丁橡胶(BR)并用胶中分布对并用胶性能的影响。结果表明:BR中炭黑的质量分数增大,NR/BR并用胶硫化胶的定伸应力、拉伸强度和拉断伸长率增大,耐磨性能提高,压缩生热和动态损耗因子减小,抗裂口增长性能变差;NR中炭黑的质量分数增大,NR/BR并用胶硫化胶的耐屈挠性能增强。     

纳米氧化锌对NR/BR胎面胶性能的影响

试验研究纳米氧化锌对不同并用比NR/BR并用胶性能的影响及其减量替代间接法氧化锌在载重轮胎胎面胶中的应用。结果表明,以纳米氧化锌等量替代间接法氧化锌用于不同并用比NR/BR并用胶中,胶料的t10和t90延长,且随着BR用量的增大,延迟时间进一步延长;硫化胶的300%定伸应力、拉断强度和回弹值增大,二者300%定伸应力和拉断强度的差值随着NR/BR并用比的变化而无明显变化,回弹值的差值随着BR用量的增大而增大;抗撕裂性能和耐疲劳性能下降;以纳米氧化锌减量25%替代间接法氧化锌用于NR/BR(并用比60/40)胎面胶中,可改善胶料的加工安全性,降低生热,提高老化后性能,成品轮胎的耐久性能有所提高。     

活化胶粉在输送带覆盖胶中的应用

研究活化胶粉用量对丁苯橡胶(SBR)性能的影响以及活化胶粉用量为45份时生胶[天然橡胶(NR)/SBR/顺丁橡胶(BR)]并用比对输送带覆盖胶性能的影响。结果表明,随着活化胶粉用量的增大,SBR胶料的定伸应力增大,拉伸强度降低,拉断伸长率和磨耗量减小,耐热老化性能改善,活化胶粉用量以45份为佳。活化胶粉用量为45份时,对于NR/SBR/BR覆盖胶,当NR用量不变时,随着SBR用量减小和BR用量增大,胶料的Fmax增大,t10缩短,硫化速率加快;当SBR用量不变时,随着NR用量减小和BR用量增大,胶料的FL和Fmax降低,t10变化不大,t90缩短,硫化效率提高。在输送带覆盖胶中加入45份活化胶粉,胶料的工艺性能好,生产成本大幅降低。     

有机硅乳液用量对天然橡胶/丁苯橡胶并用胶性能的影响

研究有机硅乳液用量对天然橡胶（NR）/丁苯橡胶（SBR）并用胶性能的影响。结果表明：随着有机硅乳液用量的增大,NR/SBR并用胶的门尼粘度和FL减小,表明有机硅乳液可改善并用胶的加工性能;NR/SBR并用胶的t10和t90缩短,表明有机硅乳液会降低并用胶的加工安全性,但可提高并用胶的硫化速率;NR/SBR并用胶的拉伸强度、拉断伸长率和撕裂强度和DIN磨耗量先增大后减小,Payne效应先增强后减弱。当有机硅乳液用量为6.8份时,NR/SBR并用胶的物理性能、耐磨性能和炭黑分散性最好。     

天然橡胶/丁苯橡胶/反式丁戊橡胶并用胶的性能研究

研究反式丁戊橡胶（TBIR）对天然橡胶（NR）/丁苯橡胶（SBR）并用胶性能的影响。结果表明：用15份TBIR替代NR,NR/SBR/TBIR并用胶的NR与SBR相容性改善,拉伸强度和定伸应力略有降低,耐磨性能、耐压缩疲劳性能和耐屈挠疲劳性能提高;用15份TBIR替代SBR,NR/SBR/TBIR并用胶的NR与SBR相容性明显改善,拉伸性能变化不大,耐磨性能、耐压缩疲劳性能和耐屈挠疲劳性能提高;用15份TBIR替代NR/SBR并用胶,NR/SBR/TBIR并用胶的大部分性能介于TBIR单独替代NR与SBR并用胶的性能之间,抗湿滑性能提高,滚动阻力降低;在NR/SBR并用胶中直接加入6份TBIR,NR/SBR/TBIR并用胶的NR与SBR相容性改善,耐磨性能、耐压缩疲劳性能和耐屈挠疲劳性能提高,抗湿滑性能和滚动阻力降低。     

原位表面改性纳米氧化锌对天然橡胶传统硫化体系硫化结构与性能的影响

采用溶胶-凝胶法制备了原位表面改性纳米Zn O,采用X射线衍射法(XRD)及透射电子显微镜(TEM)对其微观结构进行了表征,并用扫描电镜和X射线能谱仪(SEM with EDS)分析了ZnO在NR传统硫化体系(CV)硫化胶中的分散性。对比研究了使用原位表面改性纳米ZnO和普通ZnO的NR的CV硫化胶的硫化特性、拉伸性能和耐热氧老化性能,通过平衡溶胀法和化学探测剂法测定了硫化胶的硫化结构。研究结果表明,原位表面改性纳米ZnO在NR胶料中的分散性优于普通氧化锌。与加入5份普通ZnO的硫化胶相比,加入2份原位表面改性纳米ZnO的NR的CV硫化胶的拉伸强度和拉断伸长率分别提高了0.55%和10.34%。与此同时,硫化胶拉伸强度保持率和拉断伸长率保持率分别提高了35.85%和19.36%。     

石墨烯/橡胶复合材料在输送带胶料中的应用

研究石墨烯/丁苯橡胶(SBR)复合材料或石墨烯/天然橡胶(NR)复合材料在输送带胶料中的应用。结果表明:添加石墨烯可以显著提高SBR胶料和NR/SBR胶料的300%定伸应力、拉伸强度、撕裂强度和耐磨性能;石墨烯/SBR复合母胶或石墨烯/NR复合母胶(石墨烯质量分数为0. 1)用量为10～15份时,胶料的加工安全性、物理性能、耐磨性能和耐热老化性能较好;添加少量石墨烯即可提高输送带胶料的抗撕裂性能和耐磨性能,有利于延长输送带的使用寿命。     

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.     

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.     

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.     

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 $\text{Pd}\text{SiO}{}_2$.     

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.     

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.