DMC/MVQ绝缘复合材料的制备及性能表征

针对硅橡胶力学性能差的特点,本工作以硅橡胶（MVQ）为基相,以团状模塑料（DMC）为增强相,以丁苯橡胶（SBR）为相容剂来制备DMC/MVQ绝缘复合材料,研究了SBR的用量对MVQ性能的影响。结果表明：SBR和MVQ共混制得的并用胶性能要比纯MVQ的性能好,其最佳配比为DMC 60phr,SBR 25phr,MVQ 75phr;制备的复合材料体积电阻率都在4.9×1012Ω.m以上,复合材料的绝缘性能良好;通过扫描电镜分析（SEM）和动态热机械分析（DMA）,研究了复合材料的相容性,SBR的加入改善了DMC/MVQ绝缘复合材料的相容性,增加了界面相互作用,提高了DMC/MVQ绝缘复合材料的性能。     

团状模塑料增强硅橡胶绝缘材料性能的影响因素

以甲基乙烯基硅橡胶(MVQ)为基质、团状模塑料(DMC)为增强剂、丁苯橡胶(SBR)为相容剂制备DMC/SBR/MVQ绝缘复合材料,考察了SBR和DMC用量对材料力学性能、相容性、绝缘性的影响,并对材料进行了动态热机械分析、傅里叶变换红外光谱分析。结果表明,SBR作为相容剂,可以改善DMC与MVQ的相容性,提高绝缘复合材料的力学性能,在DMC/SBR/MVQ(质量比)为60/25/75时,力学性能最佳。不同质量比下的DMC/SBR/MVQ绝缘复合材料的体积电阻率都在4.8×1012Ω·m以上,绝缘性能良好;当三者质量比为60/25/75时,材料的体积电阻率最高,绝缘性最好。DMC的加入提高了SBR/MVQ绝缘复合材料的耐热性能。     

DMC/白炭黑/MVQ复合材料的制备及性能研究

采用机械共混法制备团状模塑料(DMC)/白炭黑/甲基乙烯基硅橡胶(MVQ)复合材料,并对其性能进行研究.结果表明,DMC/白炭黑/MVQ复合材料具有良好的物理性能和耐热空气老化性能,其优化配方为MVQ 100,DMC 70,白炭黑 30,氧化锌 5,硬脂酸 2,防老剂D 1,三氧化二铁 2,硫化剂DCP 6,硫黄 1,促进剂M 1;适宜的硫化条件为170 ℃/10 MPa×30 min.偏光显微镜分析表明,DMC与MVQ的相容性良好.     

白炭黑分散剂在甲基乙烯基硅橡胶/丁苯橡胶 并用胶中的应用

研究白炭黑分散剂HST和H60EF对甲基乙烯基硅橡胶(MVQ)/丁苯橡胶(SBR)并用胶性能的影响。结果表明:在MVQ/SBR并用胶中加入白炭黑分散剂HST和H60EF,可加快胶料的硫化速度,改善分散性和加工性能,提高混炼效率;白炭黑分散剂HST对MVQ/SBR并用胶的动态力学性能无明显影响,可提高撕裂强度和耐老化性能,可用作MVQ/SBR并用胶的功能性助剂。     

硅橡胶/丁苯橡胶并用胶的制备及表征

针对硅橡胶具有较高的耐热性,但力学性能差;丁苯橡胶(SBR)力学性能较好,但粘性较差;提出了将硅橡胶与SBR共混,制成共混材料;采用偏光显微镜、傅里叶变换红外光谱、差示扫描量热仪以及力学性能、热老化性能测试手段,研究了甲基乙烯基硅橡胶(MVQ)/SBR共混体系的并用比(质量比)、硫化工艺参数以及顺丁橡胶(BR)的加入对力学性能、耐热老化性能和相容性的影响。结果表明:MVQ与SBR最佳配比为30/70,白炭黑为45份;最佳硫化工艺参数为170℃×10 MPa×30 min。MVQ/SBR并用胶的玻璃化温度为-20℃,MVQ和SBR具有较好的相容性。     

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.     

混炼工艺对NR/SBR/BR/TRR农业轮胎胎面胶性能的影响

研究混炼工艺对天然橡胶(NR)/丁苯橡胶(SBR)/顺丁橡胶(BR)/轮胎再生橡胶(TRR)农业轮胎胎面胶性能的影响。结果表明:胶料混炼适合采用两段混炼工艺,一段混炼为SBR和TRR与部分炭黑混炼,二段混炼为一段混炼胶与NR、BR、剩余炭黑和其他配合剂混炼;随着一段混炼炭黑加入量增大,硫化胶的拉伸强度和撕裂强度呈增大趋势,一段混炼炭黑加入量较大时硫化胶的拉断伸长率较高,耐磨性能较好;一段混炼加入5/6炭黑的混炼工艺硫化胶的炭黑分散性较好,拉伸强度和撕裂强度较大,耐磨性能较好,生热较低,耐热氧老化和耐臭氧老化性能较好。     

有机蒙脱土对天然橡胶/丁苯橡胶的补强及增容作用

采用机械混炼法制备了天然橡胶(NR)/丁苯橡胶(SBR)/有机蒙脱土(OMMT)纳米复合材料,采用TEM和XRD对复合材料的亚微观结构进行了表征,并对复合材料的表观交联密度、静态力学性能、动态力学性能和硫化热效应进行了研究。结果表明,复合材料为剥离型纳米复合材料;OMMT能够明显提高纳米复合材料的交联密度和静态力学性能;OMMT导致NR/SBR共混胶动态损耗因子降低,并且能够促使NR和SBR玻璃化转变温度更为接近,起到了增容作用;OMMT实现了NR和SBR两相的同步硫化。     

一段混炼时间对石墨烯/天然橡胶/溶聚丁苯橡胶复合材料性能的影响

采用一段密炼和二段开炼的两段混炼工艺制备氧化石墨烯(GO)/天然橡胶(NR)/溶聚丁苯橡胶(SSBR)和还原氧化石墨烯(rGO)/NR/SBR复合材料,研究一段混炼时间对GO/NR/SSBR和rGO/NR/SSBR复合材料性能的影响。结果表明:随着一段混炼时间的延长,GO/NR/SSBR和rGO/NR/SSBR复合材料的Fmax和FL增大,t90缩短;邵尔A型硬度、300%定伸应力、拉伸强度和撕裂强度呈先增大后减小的趋势,导电性能和导热性能呈先提高后降低的趋势,气密性能呈先提高后平稳再降低的趋势。     

硅橡胶/改性蒙脱土复合材料的制备及其性能研究

以双十八烷基二甲基氯化铵(D1821)改性蒙脱土(MMT),考察了室温混炼及熔融混炼对甲基乙烯基硅橡胶(MVQ)/MMT及MVQ/MMT-D1821复合材料拉伸强度、热性能及微观形貌的影响。结果表明,改性后的MMT层间距由1.25nm扩大到了3.97nm,熔融混炼比室温混炼更有利于形成插层结构,且复合材料拉伸强度更大,当MMTD1821含量为30份(质量份,下同)时,复合材料的拉伸强度最大为6.0 MPa,但材料的热性能有所降低。     

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.