机械混炼法OMMT/PVC/NBR纳米复合材料的结构与性能

分别采用3种不同的机械混炼法制备了有机蒙脱土(OMMT)/PVC/NBR纳米复合材料,并对其结构和性能进行表征.结果表明:采用将NBR与OMMT预混再与PVC混合的方法制备的纳米复合材料具有最佳的物理性能;当OMMT用量较小时,复合材料的物理性能随OMMT用量的增大而增大;所制得的纳米复合材料为插层型纳米复合材料.     

有机蒙脱土/NR/NBR纳米复合材料的结构与性能研究

采用乳液法和机械共混法制备有机蒙脱土(OMMT)/NR/NBR复合材料,并对其微观结构、物理性能、动态力学性能和耐油性能进行研究.结果表明:大多数OMMT片层以纳米尺寸均匀分散在NR基体中;随着OMMT用量的增大,OMMT/NR/NBR复合材料物理性能和耐油性能提高;与NR /NBR并用胶相比,OMMT/NR/NBR纳米复合材料具有更低的滚动阻力.     

插层型橡胶/有机蒙脱土纳米复合材料微观结构在交联过程中的变化

采用熔体插层法制备溴化丁基橡胶(BIIR)/有机蒙脱土(OMMT)纳米复合材料和三元乙丙橡胶(EPDM)/OMMT纳米复合材料,利用X射线衍射和透射电子显微镜研究其微观结构及OMMT分散状态在硫化过程中的变化。结果表明:橡胶/OMMT纳米复合材料的插层结构在整个硫化过程中不断变化,且正硫化以后插层结构仍会随着硫化反应时间延长而发生明显改变;未硫化BIIR/OMMT纳米复合材料的插层结构层间距大于未硫化EPDM/OMMT纳米复合材料,硫化EPDM/OMMT纳米复合材料的插层结构层间距大于硫化BIIR/OMMT纳米复合材料;随着硫化程度提高,BIIR/OMMT纳米复合材料中OMMT的分散性能逐渐降低。     

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.     

橡胶/蒙脱土复合材料的制备与性能研究

用丁腈橡胶(NBR)、丁苯橡胶(SBR)和三元乙丙橡胶(EPDM)作主体材料,制备橡胶/超细全硫化粉末丁腈胶乳(UFPNBR)/蒙脱土(MMT)复合材料和橡胶/有机MMT(OMMT)复合材料,并研究其微观相态、物理性能和气密性。结果表明:在橡胶/UFPNBR/MMT复合材料中,MMT以剥离状态分散在橡胶基体中;在NBR/OMMT复合材料中,OMMT层间距较大;添加UFPNBR/MMT粉末和OMMT的橡胶/MMT复合材料物理性能和气密性随着MMT用量增大而提高;添加UFPNBR/MMT粉末和OMMT的SBR/MMT复合材料物理性能和气密性提高幅度比NBR/MMT复合材料小;OMMT对EPDM有明显的补强作用,UFPNBR/MMT粉末对EPDM几乎没有补强作用;与添加UFPNBR/MMT(质量比为1/4)粉末的EPDM/MMT复合材料相比,添加UFPNBR/MMT(质量比为1/1)粉末的EPDM/MMT复合材料气密性更好。     

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.     

熔体法OC/IIR/EPDM纳米复合材料的结构与性能研究

采用机械共混法制备有机粘土(OC)/IIR/EPDM纳米复合材料,并对其结构和性能进行研究.试验结果表明:采用机械共混法制备的OC/IIR/EPDM复合材料为插层型纳米复合材料;IIR与EPDM具有良好的相容性;当OC用量为30份、IIR/EPDM并用比为50/50时,OC/IIR/EPDM纳米复合材料的气密性能和物理性能较好.     

蒙脱土/EPDM纳米复合材料燃烧性能的研究

采用熔融插层法制备了蒙脱土/EPDM纳米复合材料,并研究了燃烧性能。结果表明,EPDM大分子不能与未有机化的钠基蒙脱土(Na+-MMT)插层复合,但能有效插入有机蒙脱土(OMMT)片层之间,形成OMMT/EPDM插层纳米复合材料。Na+-MMT对改善蒙脱土/EPDM纳米复合材料的阻燃和抑烟效果不明显;OMMT/EPDM纳米复合材料的热释放速率、总生烟量及烟密度等参数均明显降低;随OMMT用量的增大,阻燃性和抑烟性变得越来越好,最后趋于稳定。     

聚丙烯/尼龙6/纳米蒙脱石复合材料的制备及热性能研究

采用熔融插层法成功制备了聚丙烯(PP)/尼龙6(PA6)/有机化蒙脱石(OMMT)纳米复合材料.用X射线衍射分析(XRD)和透射电镜(TEM)观察了OMMT层间距的变化和材料的结构;用示差扫描量热法(DSC)和热重分析(TG)研究了热性能,并考察了纳米复合材料的拉伸强度.研究结果表明,OMMT的层间距由2.200 nm扩大到2.800 nm,PP/PA6合金高分子链取代了有机化蒙脱石层间的十六烷基三甲基溴化铵而进入到蒙脱石的片层间,加入质量分数为4%的OMMT的复合材料不仅使材料的拉伸强度提高了约15%,还提高了材料的热稳定性,使剩炭率增加了8.1%.     

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.     

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.