FKM/MVQ/FSR共混胶的性能研究

研究氟橡胶(FKM)与硅橡胶(MVQ)并用以及采用氟硅橡胶(FSR)为增容剂制作耐高低温耐油胶料的性能。结果表明：FKM并用MVQ后,热力学相容性差,因此共混胶的物性较差,但低温性能明显改善,耐油性能有所下降。随着氟硅橡胶(FSR)用量的增加,共混胶的拉伸强度和拉断伸长率均有明显的提高,耐油性略有改善,低温性能变化不大。对并用胶拉伸断裂试样断面进行电子显微镜扫描,观察到FKM/MVQ硫化胶基体断面凹凸不平,出现明显的层状分离状态,加入FSR后,可以看出FKM/MVQ/FSR硫化胶断面较为均匀,没有明显分层现象,说明FSR对FKM/MVQ 2相相容性有所改善。热失重曲线分析可看到FKM/MVQ/FSR共混胶分解温度高于FKM硫化胶的主链热分解温度,说明FKM/MVQ/FSR共混胶的耐热性优于氟橡胶。     

氟橡胶与硅橡胶共混胶的性能研究

研究了氟橡胶(FKM)与硅橡胶(MVQ)共混胶以及采用氟硅橡胶(FSR)为增容剂制作的FKM/MVQ共混胶性能。结果表明,氟橡胶与硅橡胶共混可改善氟橡胶的耐低温性能,但其力学性能降幅较大;以氟硅橡胶为增容剂可改善2种橡胶的相容性,其共混胶兼具硅橡胶的耐热性和耐寒性、氟橡胶的耐油性,成本较低。     

硅橡胶/丙烯酸酯橡胶并用胶的加工与性能

研究了甲基乙烯基硅橡胶（MVQ）／丙烯酸酯橡胶（ACM）并用胶中MVQ与ACM的配比，补强剂，加工工艺及其它添加剂对并用胶性能的影响，结果表明：MVQ与ACM并用后，其耐油性得到较大提高，且随着CM用量的增大，并用胶的耐油性逐步提高；补强剂对提高并用胶耐油性有一定作用，补强剂用量越多，并用胶的耐油性越好；补强剂的加入顺序对并用胶的各项性能有一定影响；加入羟基硅油可降低并用胶的扯断永久变形。     

硫化条件对FKM/MVQ并用胶性能的影响

采用机械共混法制备氟橡胶(FKM)/甲基乙烯基硅橡胶(MVQ)并用胶,研究硫化条件对FKM/MVQ并用胶性能的影响。结果表明,随着一段硫化温度的升高,FKM/MVQ并用胶t10和t90缩短,邵尔A型硬度和撕裂强度变化不大,定伸应力和拉伸强度先增大后减小;当一段硫化条件为165℃×t90、二段硫化条件为250℃×4h时,FKM/MVQ并用胶的综合物理性能较好。     

氟橡胶/甲基乙烯基硅橡胶共混弹性体的性能

通过机械共混法制备了氟橡胶(FKM)/甲基乙烯基硅橡胶(MVQ)弹性体,研究了二者的质量比对共混弹性体力学性能、耐油性能和动态力学性能的影响.结果表明,当FKM/MVQ(质量比,下同)为80/20时,共混弹性体具有较好的综合力学性能.随着FKM所占比例的增加,共混弹性体的耐油性能提高.当振动频率为1 Hz时,共混弹性体中MVQ相的玻璃化转变温度(Tg)比MVQ的Tg提高了约5.0 ℃,而FKM相的Tg改变不大;当FKM/MVQ为60/40时,随着振动频率由1 Hz增大到50 Hz,FKM相的Tg升高了12.9 ℃,而MVQ相的Tg变化不大.     

甲基乙烯基硅橡胶/溶聚丁苯橡胶并用胶性能的研究

研究甲基乙烯基硅橡胶(MVQ)/溶聚丁苯橡胶(SSBR)并用胶的性能,探讨并用胶表面能与耐磨和抗湿滑性能的关系。结果表明:随着MVQ用量的增大,MVQ/SSBR并用胶的物理性能和抗湿滑性能下降,摩擦因数和表面能减小,耐磨性能先提高后降低;当MVQ用量为20份时,MVQ/SSBR并用胶的综合性能最佳;MVQ/SSBR并用胶的表面能与摩擦因数和抗湿滑性能成正比;当MVQ用量小于20份时,MVQ/SSBR并用胶的表面能与耐磨性能成正比。     

乙烯丙烯酸酯橡胶共混改性硅橡胶的性能研究

将乙烯丙烯酸酯橡胶(AEM)按照不同比例与硅橡胶(MVQ)进行共混,研究并用比对MVQ/AEM并用胶的硫化特性、物理性能、耐油性能和动态力学性能的影响。结果表明:随着AEM用量的增大,MVQ/AEM并用胶的硫化时间延长,MH减小,物理性能明显改善;经过热空气老化后,并用胶的拉伸强度保持率和拉断伸长率保持率均随着AEM用量的增大而减小,耐老化性能降低;并用胶在ASTM 1#油和ASTM 3#油中浸泡后体积变化率和质量变化率减小,耐油性能改善。动态力学分析结果表明,AEM和MVQ具有良好的相容性,二者并用后低温性能下降,损耗因子逐渐增大。     

顺丁橡胶对硅橡胶/丙烯酸酯橡胶并用胶的增容作用

采用偏光显微镜、差示扫描量热仪以及力学性能、热老化性能测试手段,研究了顺丁橡胶(BR)增容的甲基乙烯基硅橡胶(MVQ)/丙烯酸酯橡胶(ACM)共混体系的并用比(质量比)、硫化工艺参数以及BR的加入对并用胶力学性能、耐热老化性能和相容性的影响。结果表明,BR的加入改善了MVQ/ACM并用胶的力学性能和耐热老化性能,当白炭黑用量为30份、BR/MVQ/ACM的并用比为25/45/55时,并用胶的力学性能和耐热老化性能最好;最佳硫化工艺参数为70℃×10 MPa×30 min;加入BR可以改善MVQ/ACM并用胶的相容性,且使其玻璃化转变温度降低,耐低温性能提高。     

碳纤维/硅橡胶/氟橡胶复合材料的制备

以硅橡胶(MVQ)/氟橡胶(FKM)并用胶为基相、碳纤维(CF)为补强相制备CF/MVQ/FKM复合材料。最佳配方为:FKM混炼胶90,MVQ混炼胶10,白炭黑20,硅烷偶联剂KH590 2.5,CF(纤维长度为12 mm)8;其中FKM混炼胶配方为FKM 100,氢氧化钙6,氧化镁3,3~#硫化剂3;MVQ混炼胶配方为MVQ 100,氧化锌3,三氧化二铁1,防老剂D 1,硫化剂DCP 5,促进剂M 1.5。最佳一段和二段硫化条件分别为170℃/10 MPa×30 min和200℃(常压)×2 h。     

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。     

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.     

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.     

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.     

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.