原位聚合甲基丙烯酸盐/低温氢化丁腈橡胶的结构与性能

采用不同阳离子的碱和甲基丙烯酸(MAA),通过混炼和硫化过程的原位聚合,制备了聚甲基丙烯酸盐(SPMAA)改性氢化丁腈橡胶(SPMAA-HNBR).用扫描电子显微镜、透射电子显微镜、傅里叶变换红外光谱仪、示差扫描量热仪及浸泡溶胀实验研究了SPMAA阳离子种类(Na+,Mg2+和Al3+)对SPMAA-HNBR性能的影响.结果表明,随着阳离子电荷数的增加,SPMAA逐渐在SPMAA-HNBR内部形成强的离子簇结构,导致其与HNBR间的相容性变差,甚至出现大尺寸的聚集体.这种明显的相分离结构造成聚甲基丙烯酸铝(Al SPMAA)改性氢化丁腈橡胶的拉伸强度和耐油溶胀性能都低于含电荷数较少的聚甲基丙烯酸钠(Na SPMAA)和聚甲基丙烯酸镁(Mg SPMAA)改性氢化丁腈橡胶的性能.各种SPMAA-HNBR的玻璃化转变温度均未发生变化,保持了-30℃的低温弹性.因此,选择生成不同阳离子的SPMAA,可在保持HNBR低温性能的基础上,有效控制SPMAA-HNBR的性能.     

甲基丙烯酸镁增强氢化丁腈橡胶的结构与形态和性能

用不同份量的甲基丙烯酸镁(MgMA)作增强剂,过氧化二异丙苯(DCP)作硫化剂,通过混炼和硫化过程的原位聚合制备了氢化丁腈橡胶/聚甲基丙烯酸镁(HNBR/PMgMA)纳米复合材料,用XRD、FTIR1、3C-NMR、SEM、TEM、DMA和交联密度分析等方法研究了其结构、形态和性能,并阐述了MgMA改性HNBR的相关机理.结果表明,MgMA在混炼过程中粒径明显变小,部分达到纳米级.硫化过程中发生原位自由基聚合,并部分接枝到HNBR分子链上,HNBR硫化胶和PMgMA有可能形成接枝互穿聚合物网络(接枝IPN).随着MgMA用量的增加,纳米复合材料硫化胶的定伸应力、拉伸强度、扯断伸长率、撕裂强度和热氧老化性能逐渐提高.当MgMA含量为30份时,体系的拉伸强度和扯断伸长率分别为38.5MPa和545%,并具有优异的热空气老化性能.MgMA能明显增加HNBR复合材料的储能模量,并降低其损耗因子.随着MgMA用量的增加,纳米复合材料硫化胶的总交联密度(Ve)和离子键交联密度(Ve2)增加,而共价键交联密度(Ve1)下降,表明离子键对HNBR/PMgMA纳米复合材料的力学性能起重要作用.     

不同压力条件下氢化丁腈橡胶的应力弛豫及分子动力学模拟研究

采用分子动力学模拟方法构建了氢化丁腈橡胶的分子链结构并计算出不同压缩比下的均方回转半径,同时对应力弛豫进行了理论预测并与压缩应力弛豫实验结果进行了对比.研究发现,均方回转半径随着压力的增大而逐渐降低,随着温度的增大而逐渐增大;在不同压力下,应力均随着时间的增大而逐渐降低而且当时间达到一定程度后应力降低逐渐平缓;计算结果表明压力增大或低温下均方回转半径小、弛豫时间长,体系越表现出弹性特征,此结果表明可用均方回转半径的变化来定量描述橡胶材料体系的应力弛豫变化,分子模拟得到的应力弛豫规律与实验结果有较好吻合.     

杂环化聚丙烯亚胺树状聚合物负载钌铑双金属纳米粒子的制备及在催化丁腈橡胶氢化中的应用

以十五元三烯氮杂大环改性的不同代数聚丙烯亚胺树状聚合物(Gn-M,n=2,3,4)为模板,通过共络合-还原方法制备了一系列钌/铑双金属纳米粒子[Gn-M(RuxRh100-x)DTNs,x为Ru摩尔分数],并将其应用于丁腈橡胶(NMR)的催化氢化.用紫外-可见光谱(UV-Vis)、X射线衍射分析(XRD)及X射线能谱(EDS)表征DTNs的金属组成和结构,结果表明,DTNs上的双金属离子被还原成金属单质并负载于Gn-M上;粒度分析结果表明,G2-M(Ru50Rh50),G3-M(Ru50Rh50)和G4-M(Ru50Rh50)DTNs的平均粒径分别为7.5,8.1和4.5 nm.凝胶测试及核磁共振波谱(1H NMR)结果表明,Ru/Rh DTNs催化剂对丁腈橡胶的催化氢化反应具有良好的选择性.当以G4-M(Ru30Rh70)DTNs为催化剂时,NBR的氢化度最高可达99.51%,循环使用2次后,丁腈橡胶的氢化度仍可达到90.58%.     

氢化可的松和表氢化可的松的密度泛函理论研究

采用密度泛函理论B3LYP/6-31G和B3LYP/6-311G*方法优化了氢化可的松和表氢化可的松的几何结构,利用优化的结构得到了氢化可的松和表氢化可的松的原子净电荷、总能量及前沿分子轨道组成.基于简谐振动分析求得了氢化可的松和表氢化可的松的红外光谱频率和强度,由统计热力学分析得到了热力学函数;进而确定了氢化可的松和...     

应用人工神经网络预测氢化可的松的溶解度

以量子化学方法在密度泛函B3LYP/6-31G(d)水平上计算得到含有电负性原子的溶剂水、醇类、酮类、酯类、氯代烷烃共17种溶剂的结构参数：最高占用轨道能(EHOMO)、分子最低空轨道能(ELUMO)、分子偶极矩(μ)、分子总能量(Etotal) 、最正原子净电荷(q+)、最负原子净电荷(q-)。采用误差反向传播(BP)算法的三层人工神经网络,确定隐含层节点数为7,建立了EHOMO、ELUMO、μ、Etotal、q+、q-、摩尔体积(VM)、介电常数(ε)、温度(T)共9个参数与氢化可的松在不同温度下不同溶剂中的溶解度之间关系的模型。运用此神经网络模型可预测不同分离条件下氢化可的松的溶解度,平均预测相对误差为7.0%。     

氢化奎尼定衍生物的合成及其催化性能研究

以价格较低的奎尼丁为原料，常压催化加氢后，采用全新的方法与1,4-二氯酞嗪、1,4-二氯苯并[G]-2,3-二氮杂萘和卤代芳烃进行偶联，合成了氢化奎尼定1,4-(2,3-二氮杂萘)二醚(8a)、氢化奎尼定1,4-(苯并[G]-2,3-二氮杂萘)二醚(8b)、氢化奎尼定1-萘醚(8c)、氢化奎尼定9-菲醚(8d)和对氯苯甲酸氢化奎尼丁酯(8e),并通过FT-IR和NMR进行表征确认其结构。选用(22E,24S)-5α-豆甾-2,22-烯-6-酮作为底物，对目标化合物进行催化性能的测试。结果表明，8b和8d的选择性更佳，ee值达到77.8%,且8b的反应时间仅需两天，回收率高达81.3%。     

利用静电界面制备高性能蒙脱石/氢化丁腈橡胶

将甲基丙烯酸(MA)和烷基胺改性蒙脱石(MMT)混合成浆料后, 加入到氢化丁腈(HNBR)橡胶中, 通过热硫化工艺, 制备了MMT/HNBR橡胶复合材料. 采用扫描电子显微镜、 透射电子显微镜、 小角X射线衍射仪、 傅里叶变换红外光谱仪和转矩流变仪研究了MA改性的MMT与橡胶间的界面及分散性, 并对复合材料的各种性能进行分析. 结果表明, 在热硫化过程中, 不仅形成了橡胶的交联网络, 而且也促使MA在橡胶中发生原位聚合. 生成的聚甲基丙烯酸与MMT表面的烷基胺形成离子对, 从而在橡胶和MMT间构筑了强的静电界面. 同时MA在MMT层间发生聚合反应, 提高了MMT在橡胶中的分散性. 动态机械性能和200%应变的应力松弛实验表明, 良好分散的MMT和静电界面有效约束了橡胶分子链在力学拉伸过程中的运动. 与纯橡胶相比, MMT/HNBR橡胶复合材料具有更大的拉伸强度和韧性. 此外, 橡胶复合材料还具有良好的N₂气阻隔性能. 因此, 配制MA/MMT浆料是一种简单方便的MMT改性方法, 制备的MMT/HNBR橡胶复合材料可用于制造具有高强韧性和气体阻隔性要求的橡胶产品.     

调控炔烃半氢化反应的催化选择性:实验和理论的最新进展（英文）

由于短链烯烃的广泛应用,炔烃选择性加氢制备烯烃是一个非常重要的石油化学催化过程.其中最简单的乙炔半氢化,吸引了众多研究者的广泛研究,是催化选择性调控的一个非常重要反应.工业上,由石油蒸汽裂解得到的乙烯往往混有微量(¹%)的乙炔,它会毒化乙烯聚合反应时所使用的Ziegler-Natta催化剂,因此需要降低乙炔含量至5×10–6以下.这要求加氢催化剂具有很高的乙炔转化率(> 99%)和乙烯选择性(> 80%).Pd基催化剂因低温下的具有高活性,是最常用的炔烃半氢化催化剂,其中Pd-Ag合金催化剂已在工业界应用了数十年.近十几年来,新型的乙炔半氢化催化剂不断被提出,其催化选择性的研究也取得了很大的进展.本文对炔烃半氢化反应的最新研究进展进行了总结.以乙炔加氢为例,介绍了其工业反应的条件、反应的网络以及潜在的副反应.归纳了提高加氢选择性的常见方法,并总结了近十几年报道的性能较好的乙炔半氢化催化剂.重点阐述了近年研究对加氢选择性的深入理解:Pd基催化剂的表面结构会随着反应条件和反应过程动态变化,从而影响加氢选择性.利用程序升温脱附和X射线光电子能谱研究催化剂的表...     

氢化丁腈橡胶/聚甲基丙烯酸镁/有机蒙脱土纳米复合材料制备及其耐介质老化性能

采用原位聚合和混炼插层相结合技术制备了氢化丁腈橡胶/聚甲基丙烯酸镁/有机蒙脱土(HNBR/PMgMA/OMT)纳米复合材料,通过XRD,SEM和TEM等测试方法研究了HNBR/PMgMA/OMT纳米复合材料的结构、形态和性能.PMgMA离子簇与未反应完全的MgMA单体形成纳米-微米共存形态结构,PMgMA对HNBR有显著的增强效果,HNBR/PMgMA/OMT纳米复合材料具有良好的加工性能、物理机械性能和耐介质老化性能.TEM结果显示MgMA/OMT并用有助于OMT剥离分散,有机蒙脱土在硫化胶中形成以剥离和插层为主、反插层和未插层共存的微观结构;SEM显示当MgMA/OMT用量为20/10份时能明显改善复合材料的界面结合,此时纳米复合材料的拉伸强度、扯断伸长率和扯断永久变形分别为30.2 MPa,520%和30%;同时具有优异的耐热空气和耐油老化性能,耐热水性能也明显改善,在165℃的热空气、水和油中长期老化14天的老化系数分别达到0.61,0.63和0.84,其耐介质老化性能明显好于炭黑增强HNBR硫化胶及HNBR/PMgMA复合材料.良好的蒙脱土片层分散结构是提高HNBR/PMgMA/OMT纳米复合材料耐介质老化性能的主要原因.     

Study on ablative properties and mechanisms of hydrogenated nitrile butadiene rubber (HNBR) composites containing different fillers

The ablative properties of hydrogenated nitrile butadiene rubber (HNBR) composites filled with fumed silica, organically modified montmorillonite (OMMT), or expanded graphite (EG) were examined. The HNBR/OMMT composite has the lowest linear ablation rate and the highest mass ablation rate and does not tend to be carbonized. On the other hand, the HNBR/EG composite has the highest linear ablation rate and the lowest mass ablation rate, and is prone to carbonization. The ablative properties of the HNBR/silica composite are between those of HNBR/OMMT and HNBR/EG. From the viewpoint of thermal shielding capability, the HNBR/OMMT has the best ablation resistance. Thermogravimetric analysis (TGA) on different HNBR composites indicated that the filler type has no significant effect on the thermal stability of the composites. To understand the ablation mechanisms, the char layers of different HNBR composites after ablation experiments were characterized by scanning electron microscopy (SEM), energy disperse X-ray spectroscopy (EDS), and wide-angle X-ray diffraction (WAXD). The results showed that the porosity in the char layers of the HNBR/OMMT composite was the highest and the corresponding structure was the loosest of the three composites. The montmorillonite (MMT) dispersed in HNBR experienced phase transition, melting and vaporization when exposed to the flame with the temperature over 2000 °C. Fumed silica only melted at such situation. On the other hand, the EG kept their original crystalline structures after the ablation test. Based on these results, the effect of the filler type on the ablation mechanisms of the HNBR composites was discussed.     

Morphology,mechanical, and fracture properties of HNBR modified ASA/SAN blends

In this work, acrylonitrile-styrene-acrylic terpolymer/styrene-acrylonitrile copolymer/hydrogenated nitrile rubber (ASA/SAN/HNBR) ternary blends with different composition were prepared by melt blending. Properties of the ternary blends were studied by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMTA), Fourier transform infrared spectra (FTIR), heat distortion temperature (HDT), melt flow rate (MFR), and Scanning electron microscopy (SEM). The results showed that the incorporation of HNBR can enhance the toughness by a large scale, and the two rubber phase showed partial miscibility. Heat resistance of the blends almost unchanged with HNBR content. FTIR told that the preparation of the ternary blends was a physical process, and no obvious phase separation was observed in SEM images.     

Electron beam modification and crosslinking: Influence of nitrile and carboxyl contents and level of unsaturation on structure and properties of nitrile rubber

The structural changes of nitrile rubber with varying nitrile contents, hydrogenated nitrile rubber and carboxylated nitrile rubber in the presence and absence of a polyfunctional monomer, namely trimethylolpropane triacrylate, at different doses of electron beam irradiation, were investigated with the help of FTIR spectroscopy (in the attenuated total reflectance mode), dynamic mechanical thermal analysis and sol–gel analysis. Solid-state NMR with gated high power decoupling technique was used to understand the mechanism of crosslinking of the irradiated samples. The allylic radicals generated in the butadiene chains react to form intermolecular crosslinkages. There was a significant decrease in the concentration of olefinic groups for the nitrile rubber on irradiation. This was also affirmed by the increase in the carbon resonances due to C–C linkages from the NMR technique, indicating more crosslinkages. The spectroscopic crosslink densities were determined and the results were compared with the swelling measurements. The variation in the crosslink clustering for rubbers with different acrylonitrile contents was explained using the NMR technique. The increase in crosslinking was also revealed by the increase in the percent gel content and dynamic storage moduli with radiation doses. The lifetime of spurs formed and the critical dose, an important criterion for overlapping of spurs, were determined for both the grafted and the ungrafted nitrile rubbers of different grades and compared using a mathematical model. The ratio of scissioning to crosslinking for nitrile rubber was determined using Charlesby–Pinner equation. The mechanical properties had also been studied for both the modified and the unmodified systems.     

Homogeneous catalytic hydrogenation of liquid carboxylated nitrile rubber

Homogeneous catalytic hydrogenation of olefinic bonds in liquid carboxylated nitrile rubber (L-XNBR) has been carried out selectively in the presence of nitrile and carboxyl functionality using a six-membered cyclopalladate complex of 2-benzoyl pyridine as catalyst. The degree of hydrogenation has been calculated from IR and NMR spectroscopic studies. For example, 68% hydrogenation has been obtained for a sample (containing 0.057 carboxyl equivalent/100 g and 26.1% acrylonitrile) under 2.7 MPa hydrogenation pressure, 0.18 mmol/L catalyst, at 333 K for 1 h in acetone solution. The overall extent of hydrogenation depends on the catalyst-to-double-bond ratio. The kinetics of hydrogenation of L-XNBR has been investigated. The reaction exhibits a pseudo-first order dependence on the concentration of the substrate. The rate constant of the reaction is reduced by the increase in carboxyl and nitrile content of the polymer. The effect of temperature on reaction kinetics has also been studied and the activation energy of hydrogenation of L-XNBR is 20.2 kJ/mol. Intrinsic viscosity of the polymer remains unchanged during the reaction. A significant lowering of the glass transition temperature and improvement of thermal stability have been observed on hydrogenation. © 1992 John Wiley & Sons, Inc.     

Development of improving processing HNBR

The hydrogenated nitrile elastomer (HNBR) is a new rubber consisting of methylene chain, cyano groups and a small number of C=C. This elastomer is produced by selection hydrogenation reaction of the olefin segments in NBR. During reaction, only the double bond should be selectively hydrogenated without the cynao groups which are essential for retaining the oil resistant properties of NBR. Present, the capacity of HNBR in total world is about 7500t/a[1],developed and commercialized by Bayer (Germany)and Zeon (Japan),trademark is THERBAN and ZETPOL respectively. In domestic, We (Lanzhou Petrochemical Company) has built a 100t/a HNBR pilot plant.As known, Mooney viscosity is a key factor in rubber processing, low Mooney viscosity will result in decreasing of strength, increasing of compression set, whereas high Mooney viscosity is hard to process, also must be plasticated. In order to overcome above problems, we designate and synthesize a base rubber as NBR-1 by modifying molecular weight distribution(MWD),its MWD is more than conventional NBR as NBR-2,correspondently their Mw, Mn and MWD are 14.9,2.2,6.78 and 13.9,4.3,3.23.Those hydrogenated product are quoted as HNBR-1 and HNBR-2.Their polymer Mooney viscosity (ML1+4 100℃) are 39 and 82.A solution of 3.5kg of NBR-1 containing 36% by weight of acrylonitrile,in 35kg of chlorobenzene and a solution of 5.5g of tris-(triphenylphosphane)-rhodium-chloride[2] in 2.5kg of chlorobenzene are introduced into a 50 liter autoclave blanketed with nitrogen. The nitrogen is replaced by hydrogen and hydrogenation is carried out for 8hr at 100℃-120℃,under a hydrogen pressure of 8 Mpa. The hydrogenation process of NBR-2 same as that of NBR-1.Their degrees of hydrogenation amount to ＞ 98%(as determined by iodine value).We find MWD of base NBR has a most effect on HNBR. Table 1 shows a comparison of physical properties of HNBR-1 and HNBR-2.As would be expected lower polymer Mooney viscosities yield lower compound Mooney viscosities.It is evident that HNBR-1 has almost the same properties in spite of lower polymer Mooney viscosities compared with HNBR-2.Table 1 Comparison of physicalproperties of HNBR-1 and HNBR-2**Compounding formulation(weight part):HNBR 100,ZnO 5.0,stearic acid 0.5,N770 carbon 50,polyester plasticizer 5.0,dicumyl peroxide 6.5,triallyl isocyanurate 1.75,styrenized diphenylamine 1.5,zinc salt of 2-mercaptobenzimidazole 0.5.     

Preparation of Hydrogenated Nitrile Rubber

Hydrogenated nitrile rubber is an oil and solvent resistant rubber and particularly give more resistant to heat, ozone, light. It is generally prepared from nitrile rubber by selective hydrogenation using a suitable catalyst system. In the present work a prepared method was adapted for the hydrogenation reaction of nitrile rubber using homogeneous tris(tri-phenlphosphine)chlorhodium(I) catalyst (RhCl(PPh3)) system. The hydrogenation reaction was carriedout at different temperature, pressure, time and catalyst concentration, the concentration, the conditions of hydrogenation are stated in table 1.     

Improving thermal and ozone stability of skim natural rubber by diimide reduction

The physical, chemical and thermal properties of diene-based polymers are improved by a chemical modification method such as hydrogenation. Skim natural rubber (SNR) which is mainly comprised of cis-1,4-polyisoprene was hydrogenated by diimide reduction in latex form, using hydrazine and hydrogen peroxide with copper sulfate as catalyst. The effect of various parameters on the level of hydrogenation calculated from proton nuclear magnetic resonance spectroscopy (¹H NMR) was investigated. The kinetic results indicated that the diimide hydrogenation of skim natural rubber latex (SNRL) exhibited a first order behavior with respect to the CC concentration. The apparent activation energy of the catalytic and non-catalytic hydrogenation of SNRL was calculated as 9.5 and 21.1 kJ/mol, respectively. From the TEM micrograph of hydrogenated SNRL particles, non-hydrogenated rubber core and hydrogenated rubber layer were observed according to a layer model. The results from thermal analysis confirmed that thermal stability of hydrogenated SNR was improved compared with the starting SNR. In addition, the thermal aging and ozone resistance of vulcanized hydrogenated SNR blends were also investigated.     

Multifunctional action of in situ formed Zn-salt of monoallylmaleamic acid

Monoallylmaleamic acid (CH₂=CH-CH”2-NH-CO-CH=CH-CO-OH; MAMA) when used in combination with zinc basic carbonate (ZBC) shows multifunctional action during processing and peroxide curing of hydrogenated nitrile rubber (HNBR). It follows from the lower viscosity, higher crosslinking degree and higher tensile strength of samples prepared from HNBR, MAMA, ZBC and peroxide, compared with the HNBR cured with the peroxide only. This kind of activity of the such system is connected with the in situ formation of very small particles of Zn-MAMA salt dispersed in the rubber matrix and in part chemically bound to the rubber.     

From exfoliation to intercalation—changes in morphology of HNBR/organoclay nanocomposites

Hydrogenated nitrile rubber (HNBR)/organoclay nanocomposites (HNBR/OCNs) were prepared by mechanical mixing technique. By altering the temperature, pressure, and treatment time, respectively, the microstructural changes of HNBR/OCNs compounds under those treatments were studied by X-ray diffraction (XRD) and transmission electron microscopy (TEM) in detail. It was investigated that after the treatment, the exfoliated organoclay dispersion in untreated HNBR/organoclay compounds transformed into the co-existing of exfoliated, intercalated, and aggregated structures by de-intercalation action. Moreover, pressure, and temperature played accelerated roles in determining the final clay structures in HNBR/OCNs. It was suggested that the transformation was caused by the relaxation of HNBR chains, and it could be proceed spontaneously in thermodynamics under the treatment condition.