偶联剂Si69原位改性淀粉/NR复合材料的性能研究

采用原位法制备偶联剂Si69改性淀粉/NR复合材料,并研究偶联剂Si69对复合材料性能的影响.结果表明:采用偶联剂Si69对淀粉进行原位改性可以增强淀粉与NR的界面相互作用,改善淀粉在NR中的分散性;偶联剂Si69与淀粉发生了化学作用,并参与了NR的硫化,从而提高复合材料的物理性能.     

酚醛树脂改性淀粉/NR复合材料的性能研究

采用间苯二酚-甲醛(RF)树脂改性淀粉,通过乳液共沉法制备淀粉/NR复合材料,研究改性淀粉用量对复合材料性能的影响,并与相同体积分数的炭黑和偶联剂Si69改性的白炭黑填充的NR复合材料进行对比。试验结果表明,RF树脂的加入增强了淀粉与NR之间的交联作用,提高了淀粉/NR复合材料的物理性能;当淀粉用量为20份、经3.6份RF树脂改性后,复合材料的综合性能最佳;随着改性淀粉用量的增大,复合材料的硬度和300%定伸应力增大。当填料体积分数相同时,改性淀粉对NR的补强效果与炭黑接近,且优于白炭黑。     

偶联剂Si69-纳米氧化锌改性槟榔纤维对天然橡胶复合材料性能的影响

以天然胶乳浸润槟榔纤维,制备天然橡胶(NR)复合材料,研究偶联剂Si69-纳米氧化锌改性槟榔纤维对NR复合材料性能的影响。结果表明:与未改性槟榔纤维的NR复合材料相比,偶联剂Si69-纳米氧化锌改性槟榔纤维的NR复合材料的物理性能、耐溶剂性能和抗湿滑性能改善,剪切模量减小,滚动阻力提高;偶联剂Si69-纳米氧化锌改性槟榔纤维的NR复合材料的综合性能优于偶联剂Si69和纳米氧化锌单独改性槟榔纤维的NR复合材料。     

有机湿法改性白炭黑对天然橡胶复合材料性能的影响

分别采用双-[3-（三乙氧基硅）丙基]-四硫化物（偶联剂Si69）、离子液体1-丁基-3-甲基咪唑六氟磷酸盐（BMI）、离子液体1-烯丙基-3-甲基氯化咪唑（AMI）对白炭黑进行改性,制备改性白炭黑/天然橡胶（NR）复合材料。研究改性剂对改性白炭黑/NR复合材料的微观结构、硫化特性、物理性能和动态力学性能的影响。结果表明：改性白炭黑的粒径明显减小,其在橡胶基体中的分散性改善,与橡胶基体之间的相互作用增强;改性白炭黑/NR复合材料的硫化速率加快,物理性能明显提高;与偶联剂Si69相比,两种离子液体明显提高改性白炭黑/NR复合材料的硫化效率和物理性能;随着应变和频率的增大,白炭黑/NR复合材料的储能模量从大到小的填料顺序为AMI改性白炭黑、BMI改性白炭黑、偶联剂Si69改性白炭黑、未改性白炭黑;AMI改性白炭黑/NR复合材料的综合性能最好。     

改性石墨对天然橡胶复合材料导热性能的影响

研究表面活性剂或不同偶联剂对石墨改性效果以及石墨用量对天然橡胶(NR)复合材料物理性能、导热性能及微观结构的影响。结果表明:偶联剂Si69对石墨的改性效果最好,石墨呈现亲油性;与未改性石墨填充NR复合材料相比,偶联剂Si69改性石墨填充NR复合材料中石墨与NR间的界面相容性得到改善,物理性能和导热性能提高;随着偶联剂Si69改性石墨用量的增大,复合材料导热性能提高,物理性能先提高后下降。当改性石墨用量为30份时,复合材料的综合性能较好。     

高性能羧基化多壁碳纳米管/NR复合材料的制备、结构与性能

以超声分散的羧基化多壁碳纳米管(MC)悬浮液填充天然胶乳,采用喷雾干燥法制备MC/NR复合材料,研究偶联剂Si69和KH-550改性对复合材料中填料分散及各项性能的影响.结果表明:喷雾干燥法制备的MC/NR复合材料中碳纳米管分散较好;偶联剂Si69和KH-550与MC表面的羧基发生了化学反应,使其在复合材料中的分散得到进一步改善;当MC用量高于10份时,KH-550改性MC/NR复合材料表现出优异的物理性能和导电性能.     

气膜包覆法制备Si69改性淀粉/天然橡胶复合材料的性能

采用气膜包覆法制得双(3 -三乙氧基硅烷丙基)四硫化物(简称Si 69)改性淀粉,然后与天然橡胶(NR)共混制得Si 69改性淀粉/NR复合材料,研究了Si 69改性淀粉的疏水性,考察了Si 69用量对复合材料硫化特性、物理机械性能、加工性能及动态性能的影响,并表征了复合材料的相态结构.结果表明,经气流粉碎后淀粉的平均...     

液相改性对白炭黑表面活性位点的影响

先采用偶联剂KH590与分散剂MOA液相改性白炭黑制备改性白炭黑水浆,然后分别制备干法混炼和湿法混炼天然橡胶(NR)/白炭黑母炼胶,再在后期混炼时补加偶联剂Si69,通过制备NR/白炭黑纳米复合材料并对其性能进行研究,考察液相改性后的白炭黑表面是否还有剩余活性位点与偶联剂Si69反应。结果表明,后期补加的偶联剂Si69无法接枝在白炭黑表面而起到偶联作用,不能改善白炭黑在橡胶基体中的分散性和NR/白炭黑纳米复合材料的性能,液相改性后的白炭黑表面活性位点已全部被占据。     

淀粉/炭黑/SBR/BR复合材料的性能研究

采用改性淀粉部分替代炭黑制备淀粉/炭黑/SBR/BR复合材料,研究间苯二酚-甲醛(RF)树脂或偶联剂KH-550改性淀粉对复合材料性能的影响.结果表明:偶联剂KH-550的改性效果优于RF树脂;RF树脂或偶联剂KH-550能够对淀粉和橡胶基体的界面起到增强作用;与加入RF树脂改性淀粉的复合材料相比,加入偶联剂KH-550改性淀粉的复合材料耐磨性能较差,但抗湿滑性能较好.     

乳液共凝法制备纳米四氧化三铁/NR复合材料的研究

试验研究硅烷偶联剂种类和用量以及复合材料制备方法对纳米四氧化三铁/NR复合材料物理性能的影响.结果表明,硅烷偶联剂可有效地对纳米四氧化三铁表面进行改性;透射电子显微镜、扫描电子显微镜和红外光谱分析结果表明,偶联剂Si69的改性效果较好,增强了纳米四氧化三铁/NR复合材料的界面作用,促进了纳米四氧化三铁粒子在NR中分散,改善了复合材料的结构和性能;当偶联剂Si69用量为2.25份时,纳米四氧化三铁/NR复合材料的综合物理性能最好.与机械共混法和磁流体-凝胶法相比,乳液共凝法制备纳米四氧化三铁/NR复合材料的物理性能较优.     

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.