BR/CB/OMMT纳米复合材料的结构与性能研究

采用溶液插层法与双辊混炼法制备了顺丁橡胶/炭黑/有机蒙脱土（BR/CB/OMMT）纳米复合材料,用透射电子显微镜（TEM）以及X射线衍射（XRD）方法对复合材料的亚微观结构进行了表征,并研究了复合材料的力学特性、耐磨耗性能以及硫化特性。结果表明：BR/CB/OMMT为插层型纳米复合材料;在OMMT含量小于4份时,BR/CB/OMMT纳米复合材料具有优异的力学性能和耐磨耗性能;OMMT起到了硫化促进剂的作用,降低了BR的焦烧时间（TS）和正硫化时间（T90）;低填充量OMMT可提高复合材料的交联密度。     

顺丁橡胶/天然橡胶/有机蒙脱土纳米复合材料的研究

采用溶液插层法和双辊混炼法制得了BR/NR/OMMT纳米复合材料,进行了透射电镜分析,研究了复合材料的力学性能、磨耗性能以及耐溶剂性能.结果表明,OMMT在BR/NR基体中分散均匀,BR/NR/OMMT纳米复合材料是一种剥离型纳米材料.与BR/NR复合材料相比,BR/NR/OMMT纳米复合材料具有优异的力学性能、磨耗性能和耐溶剂性能.     

顺丁橡胶/有机蒙脱土纳米复合材料的结构与性能

采用溶液法制得了顺丁橡胶(BR)有/机蒙脱土(OMMT)纳米复合材料,并用X射线衍射仪、透射电子显微镜对复合材料的结构进行了表征,研究了复合材料的应力-应变行为和耐油性能。结果表明,OMMT的层间距增大,制得了插层型纳米复合材料;在较高的应变下,BR/OMMT纳米复合材料的扯断伸长率和拉伸强度随OMMT用量的增大而增加;当OMMT用量小于9份时,BR/OMMT纳米复合材料的耐油性能随OMMT用量的增加而有所提高。     

OMMT/BIIR纳米复合材料的结构与性能研究

采用熔体插层法制备有机蒙脱土(OMMT)/BIIR纳米复合材料.结果表明,OMMT/BIIR纳米复合材料是有序插层型纳米复合材料,在OMMT用量(0～15份)较小的情况下,其物理性能随着OMMT用量的增大明显提高;与BIIR胶料相比,其气密性优异.     

NR/BR/OMMT纳米复合材料的结构与性能研究及其在轮胎胎面胶中的应用

采用机械混炼法制备了天然橡胶/顺丁橡胶/有机蒙脱土(NR/BR/OMMT)纳米复合材料,并对复合材料的结构与性能进行了表征。OMMT可明显提高橡胶基体的耐油性能和物理机械性能,降低混炼胶的焦烧时间(Ts)和正硫化时间(T90),起到了促进硫化作用。轮胎胎面胶配合显示,OMMT与炭黑并用补强NR/BR共混胶,明显改善其力学性能与耐磨耗性能。     

有机蒙脱土对天然橡胶/顺丁橡胶纳米复合材料的增强及增容作用

采用机械混炼法制备了天然橡胶/顺丁橡胶/有机蒙脱土(NR/BR/OMMT)纳米复合材料,用透射电子显微镜以及广角X射线衍射仪研究了OMMT在纳米复合材料中的分布以及相结构,并对复合材料的力学性能、动态力学性能以及硫化热效应进行了研究。结果表明,OMMT多数分布于NR相以及NR和BR两相界面处,少数分散在BR相中;当OMMT少于6份时,OMMT片层呈剥离状态,并以纳米尺寸分散于橡胶基体中;纳米复合材料的硬度、拉伸强度和定伸应力随OMMT用量的增加而增大,但超过8份时,纳米复合材料的拉伸强度略有下降;与NR/BR复合材料相比,NR/BR/OMMT纳米复合材料的损耗因子降低,但具有相似的滚动阻力和更好的抗湿滑性能;OMMT能起增容作用,实现NR和BR两相的同步交联。     

顺丁橡胶/有机蒙脱土纳米复合材料的拉伸应力-应变行为Ⅰ.应力-应变曲线及其理论模拟

用二甲基双氢化牛脂基氯化铵改性的钠基蒙脱土(Na-MMT)通过熔融共混法制备了插层型顺丁橡胶(BR)／有机蒙脱土(OMMT)纳米复合材料,研究了单轴拉伸时Na-MMT、0MMT、白炭黑及炭黑增强BR的应力-应变行为,采用Gregory提出的储能函数形式描述了Na-MMT、OMMT、白炭黑及炭黑增强BR的拉伸应力-应变曲线。结果表明,BR／OMMT纳米复合材料的力学性能优于Na-MMT填充BR硫化胶;当应变为0-900％时,根据储能函数形式所得到的应力-应变理论曲线均能与实验数据很好的符合。     

乳液插层法制备丁苯橡胶/有机蒙脱土纳米复合材料

对蒙脱土(MMT)进行了有机化改性,采用乳液插层法制备了丁苯橡胶(SBR)/有机蒙脱土(OMMT)纳米复合材料,用透射电子显微镜、X射线衍射法对OMMT及复合材料进行了表征,研究了复合材料的物理机械性能及动态力学性能.结果表明,MMT的层间距为1.47 nm,OMMT的层间距增大到2.94 nm;OMMT片层均匀分散在SBR基体中,具有良好的界面相容性;随着OMMT用量的增加,SBR/OMMT纳米复合材料的物理机械性能明显改善,且具有低填充量高增强效果的特点;SBR/OMMT纳米复合材料具有与SBR/炭黑N 330复合材料相当的抗湿滑性能,同时具有更小的滚动阻力.     

硅烷偶联剂对OMMT/NR纳米复合材料结构与性能的影响

采用混炼插层法制备有机蒙脱土(OMMT)/NR纳米复合材料,研究硅烷偶联剂对其结构和性能的影响.结果表明,与NR相比,OMMT/NR纳米复合材料的物理性能,热稳定性和动态力学性能均有所提高;采用硅烷偶联剂KH-560改性的OMMT制备的纳米复合材料各项性能均优于采用硅烷偶联剂KH-550改性的OMMT制备的纳米复合材料.     

端羟基聚丁二烯/聚氨酯/有机蒙脱土纳米复合材料的制备及性能

以双羟乙基甲基氢化牛脂基氯化铵为插层剂,采用单体插层法制备了端羟基聚丁二烯(HTPB)、聚氨酯(PU)和有机蒙脱土(OMMT)纳米复合材料.当OMMT为3质量份时,HTPB/PU/OMMT纳米复合材料的T型剥离强度是HTPB/PU复合材料的2.58倍.X射线衍射和透射电镜分析表明,OMMT在HTPB/PU/OMMT纳米复合材料中呈剥离状态.     

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.     

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.     

Participation of lewis base on vinyl chloride polymerization with Al(C2H5)3CCl4 catalyst system

The polymerization of vinyl chloride has been investigated using an $\text{Al}\text{(}\text{C}{}_2\text{H}{}_5\text{)}{}_3\text{CCl}{}_4$ catalyst system in the presence of various Lewis bases. Effective Lewis bases are γ-butyrolactone, diglyme and diethylenetriamine which are multidentate. The rate of polymerization is dependent not only on the basicity of the Lewis base used but also on a coordination number of one. The latter is the predominant factor. For the effect of polymeric amines, a tentative hypothesis is discussed.     

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.     

Synthesis and Characterization of Ti0.33Ta0.33Nb0.33C and Ti0.33Ta0.33Nb0.33CxN1-x Whiskers

Ta_0.33Ti_0.33Nb_0.33C and Ta_0.33Ti_0.33Nb_0.33C _x N_{1− x} whiskers were synthesized via a carbothermal vapor-liquid-solid growth mechanism in the temperature range 900°-1450°C in Ar or N₂. The optimum temperature was 1250°C. Whiskers were obtained in a yield of 70-90 vol%. The whiskers were 0.5–1 µm in diameter and 10–30 µm in length. The starting materials that produced the highest whisker yield were: TiO₂, Ta₂O₅, Nb₂O₅, C, Ni, and NaCl. C was added to reduce the oxides, and Ni to catalyze whisker growth. NaCl was used as a source of Cl for vapor-phase transportation of Ta and Nb oxochlorides and Ti chlorides to the catalyst. The catalyst metal was recycled several times during the synthesis and was transported as NiCl₂( g ) according to thermodynamic calculations. The rate of formation and the chemical composition of the whiskers depended on the synthesis temperature, the choice of catalyst, and the atmosphere. At low temperatures, the whiskers were enriched in Nb and Ta, whereas the Ti content increased with increased synthesis temperature.