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.     

有机蒙脱土/聚氨酯/端羟基聚丁二烯液体橡胶纳米复合材料的制备

采用单体插层法制备了有机蒙脱土(OMMT)/聚氨酯(PU)/端羟基聚丁二烯液体橡胶(HTPB)纳米复合材料,通过正交试验研究了OMMT用量、甲苯二异氰酸酯(TDI)用量、加料方法及试验温度对复合材料作为胶黏剂使用时的T型剥离强度的影响.结果表明,OMMT/PU/HTPB复合材料的最佳制备条件为OMMT 3份(质量,下同),TDI18份,采用分步加料方式,在60℃下进行反应.所得复合材料作为胶黏剂使用时其T型剥离强度比未添加OMMT的空白试样高出218.1%.X射线衍射分析表明OMMT在PU/HTPB基质中达到了全剥离的程度.     

PU/有机蒙脱土纳米复合材料的制备和性能研究

采用原位插层聚合法制备PU/有机蒙脱土(OMMT)纳米复合材料。通过X射线衍射和透射电镜分析发现,当OMMT质量分数为0 01和0 03时,OMMT完全剥离并较均匀地分散于PU基体中;当OMMT质量分数为0 05时,OMMT在PU基体中发生部分剥离。热重分析表明,加入OMMT可提高复合材料的耐热性。动态力学分析表明,OMMT对PU模量的影响不大。PU/OMMT复合材料的硬度、弹性模量、拉伸强度和拉断伸长率均比纯PU有所提高。     

PU/OMMT纳米复合材料的制备与性能研究

采用单体插层聚合方法制备聚氨酯（PU）／有机蒙脱土（OMMT）纳米复合材料,并对其结构和性能进行分析。结果表明，经双羟乙基十二烷基三甲基氯化铵改性得到的OMMT（DK2）层间距较大；DK2质量分数为0．03时,PU／OMMT纳米复合材料中OMMT剥离程度较大，PU的插层效果较好,复合材料的物理性能和热稳定性能优良。     

甲基乙烯基硅橡胶/有机蒙脱土母炼胶纳米复合材料的制备、结构与性能

采用溶液插层法和母炼胶混炼工艺制备了甲基乙烯基硅橡胶(MVQ)/有机蒙脱土母炼胶(OMMT-MB)纳米复合材料,通过X射线衍射(XRD)、透射电子显微镜(TEM)对复合材料进行了表征,研究了复合材料的拉伸性能与热稳定性能,并与直接共混法制备的MVQ/有机蒙脱土(OMMT)复合材料和MVQ/白炭黑复合材料进行了对比,分析了OMMT的增强机理.结果表明,MVQ/OMMT-MB纳米复合材料中的OMMT完全剥离,且均匀分散在MVQ基体中;当OMMT质量分数为20%时,MVQ/OMMT-MB复合材料的拉伸性能优于MVQ/OMMT复合材料,拉伸强度和扯断伸长率分别增大至1.41 MPa、490%;其与MVQ/白炭黑复合材料相比,两者的拉伸强度相当,扯断伸长率增大了30%;MVQ/OMMT-MB复合材料的热稳定性略优于MVQ/OMMT复合材料,但比MVQ/白炭黑复合材料差.     

HOMMT/MVQ纳米复合材料的制备与性能研究

采用超支化技术对有机蒙脱土(OMMT)进行改性制备超支化有机蒙脱土(HOMMT),并制备HOMMT/甲基乙烯基硅橡胶(MVQ)纳米复合材料,对其性能进行研究。结果表明,HOMMT呈剥离纳米片层结构,与OMMT相比,HOMMT耐热性能提高;随着HOMMT用量的增大,HOMMT/MVQ复合材料拉伸强度减小;与MVQ硫化胶相比,当HOMMT用量为1份时,HOMMT/MVQ纳米复合材料拉伸强度提高了28%,拉断伸长率提高了67%,起始降解温度升高了25℃。     

OMMT/NR纳米复合材料的性能研究

采用两种有机蒙脱土(OMMT)通过机械混炼法制备OMMT/NR纳米复合材科,并对复合材料的各项性能进行研究.结果表明,与NR相比,OMMT/NR纳米复合材料的加工性能、物理性能、热稳定性能和动态力学性能均有明显改善;以N,N'-二甲基-烷烃铵盐作为蒙脱土改性剂制备的OMMT/NR纳米复合材料的加工性能和物理性能较好.     

PP/PP-g-MAH/OMMT纳米复合材料流变性能

采用自制聚丙烯(PP)接枝马来酸酐(PP-g-MAH)作为相容剂,与经有机化改性的蒙脱土(OMMT)通过熔融插层法制备了PP/PP-g-MAH/OMMT纳米复合材料,对其加工和流变性能进行了研究.结果发现,随着OMMT用量增加,PP/OMMT和PP-g-MAH/OMMT纳米复合材料的熔体流动速率(MFR)有下降的趋势;...     

塑料改性用有机膨润土制备技术及应用的研究

本文采用不同的有机改性剂制备出有机膨润土(OMMT),并用所制备的有机膨润土分别制备出PU/OMMT、PBT/OMMT、PA6/OMMT纳米复合材料.经对复合材料力学性能分析结果表明:用N-烷基氨基酸改性膨润土所制备PU/OMMT、PA6/OMMT纳米复合材料性能最佳;用十六烷基三甲基溴化铵改性膨润土所制备PBT/OMMT纳米复合材料性能最佳.     

PU/OMMT纳米复合材料的制备与性能研究

采用一步法和预聚体法制备聚氨酯（PU）／有机蒙脱土（OMMT）纳米复合材料，研究分散方式对OMMT层间距以及复合材料制备方法和OMMT用量对纳米复合材料拉伸性能的影响。结果表明，采用高速剪切分散法和超声波分散法均可使聚四氢呋喃醚二醇分子链进入OMMT片层间，增大其层间距；预聚体法PU／OMMT纳米复合材料拉伸性能优于一步法复合材料；与PU弹性体相比，当OMMT用量为0．5份时，一步法复合材料的强度和韧性均提高。牌号为DKIN的OMMT用量为7份时。复合材料的拉伸强度提高54％，拉断伸长率提高19．4％，增幅最大。     

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.