废聚氨酯改性热塑性弹性体SBS的性能研究

以废聚氨酯(PU)改性热塑性弹性体苯乙烯-丁二烯-苯乙烯共聚物(SBS),探讨了废PU用量、相容剂对废PU/SBS复合材料的物理机械性能的影响以及废PU对含填料轻质碳酸钙(CaCO3)的SBS性能的影响;并采用相差显微镜观察了复合材料的亚微观结构.结果表明,废PU质量在15份左右时,废PU/SBS复合材料的综合性能最佳;相容剂虽然能够改善复合材料的界面,但是对宏观力学性能影响不大;废PU能够很好地改善CaCO3 /SBS的界面性质,同时大幅度提高了物理机械性能,用废PU改性的CaCO3/SBS材料具有较高的性价比.     

P(St/MAH/BA)改性纳米CaCO3对PS的增韧研究

采用由苯乙烯(St)、马来酸酐(MAH)和丙烯酸丁酯(BA)组成的三元聚合物P(St/MAH/BA)作为纳米CaCO3-的表面改性剂,制备了纳米CaCO3/PS复合材料,并对复合材料的力学性能进行了测试.结果表明,P(St/MAH/BA)作为纳米CaCO3表面改性剂与PS的相容剂能够明显改善纳米CaCO3/PS复合材料的力学性能,经P(St/MAH/BA)改性的纳米CaCO3对PS具有明显的增韧改性作用.     

SEBS/PP热塑性弹性体的制备与性能研究

以苯乙烯-乙烯-丁二烯-苯乙烯嵌段共聚物(SEBS)和聚丙烯(PP)为基体树脂,以碳酸钙(CaCO3)为填充材料,用氢化白油调节其硬度及加工流动性,在一定的工艺条件下添加助剂用开炼机混炼制备SEBS/PP热塑性弹性体;研究了氢化白油、CaCO3和热塑性弹性体等对SEBS/PP共混体系性能的影响。     

废聚氨酯改性热塑性弹性体SBS性能的研究

研究了废聚氨酯(PU)改性热塑性弹性体苯乙烯-丁二烯-苯乙烯(SBS)共聚物的性能;探讨了废PU用量、相容剂和轻质碳酸钙(CaCO3)对废PU/SBS复合材料物理机械性能的影响;用相差显微镜观察了复合材料的亚微观结构.结果表明,废PU用量为15份时,废PU/SBS复合材料综合性能最佳;相容剂虽然能够改善复合材料的界面状态,但对力学性能影响不大;废PU能够很好地改善CaCO3 /SBS的界面性质,同时大幅度地提高了物理机械性能,是一种具有高性能价格比的热塑性弹性体材料.     

ABS/HIPS相容性的研究

采用苯乙烯-马来酸酐共聚物(SMA)作为丙烯腈-丁二烯-苯乙烯共聚物/高抗冲聚苯乙烯(ABS/HIPS)的相容剂,研究了SMA对ABS/HIPS共混体系力学性能的影响,并用扫描电子显微镜对共混物的亚微观形态结构进行了分析。结果表明,SMA的加入起到了很好的增容作用。随着HIPS/SMA用量的增加,共混物的冲击性能先增大后减小,当HIPS/SMA=8.5/1.5(质量比),且HIPS/SMA质量分数为10%时,共混物的缺口冲击强度达到97.1J/m,同时拉伸强度和弯曲强度最大。     

PC/ABS共混改性研究

研究了甲基丙烯酸甲酯/丁二烯/苯乙烯共聚物(MBS)作为相容剂对聚碳酸酯(PC)/丙烯腈-丁二烯-苯乙烯共聚物(ABS)共混体系相容性、力学性能、形态结构以及动态力学性能的影响.结果表明,随着MBS添加量的增加,PC/ABS的缺口冲击强度和断裂伸长率呈先增大再减小的趋势,拉伸强度和弯曲强度都呈下降趋势;加入MBS后,PC/ABS的分散相粒径明显减小,PC与ABS两相的玻璃化转变温度相互靠拢,因而PC/ABS的相容性得到显著改善.     

SBS和纳米CaCO_3增容PP/SAN体系的研究

研究了苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS)单独添加和与纳米CaCO3复配添加对聚丙烯/苯乙烯-丙烯腈共聚物(PP/SAN)共混体系相容性的影响。结果表明:SBS用量为6 phr时,体系的分散性尺寸降低,分布均匀性改善,有一定的增容效果,但当其用量为10 phr时,体系的相容性变差;SBS和纳米CaCO3先在双辊塑炼机上混炼后再复配添加,当纳米CaCO3/SBS质量比为2/1、总添加量为10 phr时,增容效果好于单独添加SBS的体系;改变纳米CaCO3/SBS的配比体,系的拉伸强度和缺口冲击强度变化不大。     

ABS/PA6共混体系的反应性增容研究

用少量苯乙烯-马来酸酐(SMA)作为相容剂改善ABS/PA6共混体系的相容性,研究了共混体系(固定ABS/PA6质量比为70/30)中相容剂的最佳用量,以及随相容剂含量变化引起的体系形态结构和力学性能变化情况,同时探讨了体系组成与性能关系的微观机理。还研究了环境因素对ABS/PA6共混体系性能的影响。     

PA6/SEBS-g-MAH/OMMT/GMA共混物的制备和性能研究

以马来酸酐(MAH)接枝苯乙烯-(乙烯-丁烯)-苯乙烯共聚物SEBS(SEBS-g-MAH)为增韧剂,有机蒙脱土(OMMT)为增强填料,甲基丙烯酸缩水甘油酯(GMA)为相容剂,采用熔融挤出方法制备了PA6/SEBS-gMAH/OMMT复合材料.通过力学、毛细管流变性能测试,考察了SEBS-g-MAH、OMMT和GMA对共混物的力学性能及流变性能的影响.结果表明,共混材料能在保持基本强度及模量稳定的情况下提高冲击强度,获得良好的综合力学性能.PA6及其共混物均为假塑性流体,在230～260℃共混材料的非牛顿指数为0.603～0.931,表观黏度随着剪切应力的增加而降低;加入SEBS-g-MAH、OMMT和/或GMA使得PA6的表观黏度增大,黏流活化能降低;在恒定剪切应力下PA6共混物可在较宽的温度范围内成型加工.     

相容剂SEBS-g-MAH对回收HIPS、ABS的共混物流变性能的影响

以苯乙烯-乙烯-丁烯-苯乙烯嵌段共聚物接枝马来酸酐(SEBS-g-MAH)为相容剂制备了回收高冲击强度聚苯乙烯(HIPS)和丙烯腈-丁二烯-苯乙烯共聚物(ABS)的共混物。利用熔体质量流动速率试验机和毛细管流变仪分析研究了该HIPS/ABS/SEBS-g-MAH共混物的流变行为。结果表明:在测试温度、应力条件下,该HIPS/ABS/SEBS-g-MAH共混物均为假塑性流体;随着相容剂SEBS-g-MAH用量的增加,共混物的非牛顿指数和黏流活化能均先增大后减小,且在相容剂SEBS-g-MAH用量为15 phr时达到最大值。     

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.     

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.     

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.     

Synthetic routes to nanoscale BxCyNz architectures

B_xC_yN_z nanoscale materials, hybrids of h-BN and graphite, have been recently synthesised using various techniques. Here, we present the latest advances in the synthesis and characterisation of B-C-N nanotubes and nanofibres. In particular, we focus on layered BC₂N, BN, BC and CN_x systems, reviewing their production methods as well as their structural and electronic properties. These materials may find important applications in the fabrication of nanotransistors, robust nanocomposites, conducting polymers, storage components and field emission sources.     

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.     

The System Si3N4-SiO2-Y2O3

Subsolidus phase relations were established in the system Si₃N₄-SiO₂-Y₂O₃. Four ternary compounds were confirmed, with compositions of Y₄Si₂O₇N₂, Y₂Si₃O₃N₄, YSiO₂N, and Y₁₀(SiO₄)₆N₂. The eutectic in the triangle Si₃N₄-Y₂Si₂O₇-Y₁₀(SiO₄)₆N₂ melts at 1500°C and that in the triangle Si₂N₂O-SiO₂-Y₂Si₂O₇ at 1550°C. The eutectic temperature of the Si₃N₄-Y₂Si₂O₇ join was ∼ 1520°C.