动态硫化PP/EPDM热塑性弹性体的研究进展

阐述了动态硫化聚丙烯(PP)/三元乙丙橡胶(EPDM)共混型热塑性弹性体的发展历史和发展状况;概述了动态硫化PP/EPDM共混型热塑性弹性体的硫化体系及硫化原理;总结了共混体系的成份配置和工艺条件对PP/EPDM共混物性能和结构的影响;简述了动态硫化PP/EPDM热塑性弹性体的研究现状与应用;最后展望了动态硫化PP/EPDM热塑性弹性体的发展趋势。     

过氧化物动态硫化三元乙丙橡胶/聚丙烯的动力学行为

通过无转子硫化仪研究了三元乙丙橡胶(EPDM)/聚丙烯(PP)动态硫化特性及动力学,并考察了硫化体系及硫化温度对EPDM/PP动态硫化特性及动力学参数的影响.结果表明,过氧化物动态硫化EPDM/PP过程主要由主硫化阶段及后硫化阶段2个一级动力学反应组成;通过对两段硫化反应速率常数的拟合发现硫化剂BIBP、助硫化剂HVP...     

丁腈橡胶/聚丙烯热塑性弹性体的产业化研究

研究了三乙烯四胺(TETA)、马来酸酐接枝聚丙烯(MP)和羧基丁腈橡胶(XNBR)对丁腈橡胶(NBR)/聚丙烯(PP)共混体系的增容机理,并通过红外光谱对其机理进行了表征。采用双螺杆挤出机作为动态硫化设备,研究了偏苯三酸三辛酯(TOTM)对NBR/PP体系的增塑效果;同时考察了硅土和碳酸钙填料对体系性能的影响。结果表明,碳酸钙是该体系较好的填料体系。     

聚丙烯/有机硅橡胶热塑性弹性体的制备及性能

采用动态硫化法制备了聚丙烯(PP)/有机硅橡胶(SR)动态硫化热塑性弹性体(TPV),考察了PP/SR的质量比对PP/SR TPV的力学性能、流变行为及结晶行为的影响。结果表明,PP/SR TPV在动态硫化前后微观结构发生了由双连续相结构向"海-岛"结构的转变。随着SR用量的增加,PP/SR TPV的拉伸强度、扯断伸长率及撕裂强度下降;体系的结晶焓下降,PP相的结晶度下降,PP/SR TPV的复数黏度升高,但在高频时,SR对体系的复数黏度影响不大。     

动态硫化对SBS/PP热塑性弹性体的影响

采用动态硫化法制备苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS)/聚丙烯(PP)热塑性弹性体,研究了硫化体系、硫化剂含量和橡塑比对SBS/PP共混物的力学性能、结晶与熔融行为、热稳定性、耐溶剂性的影响。结果表明,采用硫黄硫化体系弹性体的力学性能要优于采用过氧化二异丙苯(DCP)和酚醛树脂硫化体系的弹性体,且最佳硫化剂用量为1.5份;SBS/PP弹性体的最佳橡塑质量比为80/20;动态硫化使SBS/PP弹性体的结晶温度升高,热稳定性增强,耐溶剂性提高。     

动态硫化PP/POE/胶粉热塑性弹性体的性能研究

研究动态硫化聚丙烯(PP)/聚烯烃弹性体(POE)/胶粉热塑性弹性体的性能。结果表明,动态硫化能有效提高热塑性弹性体的物理性能和耐热氧老化性能;炭黑对动态硫化PP/POE/胶粉热塑性弹性体有较好的补强作用,其补强弹性体的再加工性能和热氧老化性能较优。     

聚烯烃弹性体/聚丙烯热塑性弹性体的制备及力学性能

以过氧化物为硫化剂,用动态硫化法制备了聚烯烃弹性体(POE)/聚丙烯(PP)热塑性弹性体,研究了硫化剂用量、填料种类和加工次数对体系力学性能的影响。结果表明,增加硫化剂用量可以提高体系的拉伸强度,降低拉伸永久变形和压缩永久变形。碳酸钙和滑石粉对POE/PP体系无明显增强作用,炭黑的增强作用较此二者明显一些,这三种填料加入后都会使体系的扯断伸长率降低而硬度增大。加入石蜡油会使体系的扯断伸长率和压缩永久变形增大、硬度和拉伸强度降低。加工次数对POE/PP体系的力学性能无明显影响,说明体系具有较好的重复加工性能。     

石墨烯/多壁碳纳米管/热塑性硫化胶复合材料的制备及性能

通过熔融接枝共混制备了石墨烯(Ge)/多壁碳纳米管(MWCNTs)/聚丙烯(PP)母粒,然后与丁基橡胶动态硫化制备了Ge/MWCNTs/热塑性硫化胶(TPV)复合材料,考察了Ge/MWCNTs/TPV复合材料的相态结构、热电性能和力学性能.结果表明,Ge/MWCNTs作为异相成核剂能够提高PP的结晶温度;Ge/MWCN...     

加工方法对动态硫化的聚丙烯/三元乙丙橡胶/甲基丙烯酸锌复合材料的力学性能影响

通过三种不同的加工手段,制备了动态硫化的聚丙烯(PP)/三元乙丙橡胶(EPDM)/甲基丙烯酸锌(ZDMA)复合材料。结果表明,Haake密炼机制备的复合材料综合性能较佳,并且较低的加工温度能够获得综合性能较好的PP/EPDM/ZDMA复合材料。力学性能的数据表明,EPDM的加入,在降低了PP拉伸强度的同时,增加了PP的韧性,而加入ZDMA则进一步提高了复合材料的冲击强度。     

有机蒙脱土/丁基橡胶/聚丙烯热塑性硫化胶的制备与性能

采用动态硫化法制备了有机蒙脱土(OMMT)/丁基橡胶(IIR)/聚丙烯(PP)热塑性硫化胶(TPV),考察了OMMT的用量和IIR/PP的质量比对TPV的物理机械性能、动态力学性能及热性能的影响.结果表明,当OMMT的用量为20份时,TPV的物理机械性能较佳,Payne效应最弱,OMMT均匀地分布在基体中,阻尼性能较好...     

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.     

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.