用核磁共振法研究促进剂对硫黄硫化天然橡胶结构的影响

用核磁共振交联密度仪研究了次磺酰胺类促进剂NS、DZ和CZ对天然橡胶硫化胶结构的影响,考察了相同用量下促进剂种类与天然橡胶硫化胶交联密度的关系.结果表明,在基本配方和硫化条件相同的情况下, 促进剂的相对分子质量越低,天然橡胶硫化胶的交联密度越高.硫化胶的交联密度不仅对核磁共振的横向弛豫时间有影响,而且影响其纵向弛豫时间.随着交联密度的增加,硫化胶的核磁共振弛豫时间缩短,弛豫时间对温度的依赖性减弱.     

用核磁共振法研究微生物凝固天然橡胶硫化过程交联密度的变化

采用核磁共振交联密度仪,考察了微生物凝固天然橡胶在硫化过程交联密度(XLD),网链含量(AMc),自由小分子含量(AT2)以及相邻交联点间的质量(Mc)的动态变化规律。结果表明,硫化初期,XLD和AMc随硫化时间增加急剧增大,但t50后增速降低,并逐步趋于稳定。与AMc相反,自由悬挂链末端及活动性强的小分子等部分的含量(AT2)随着硫化时间的增加而降低,并逐步趋于稳定。橡胶交联点间的相对分子质量(Mc)与交联密度成反比。     

使用核磁共振交联密度仪测试不同方法凝固天然橡胶的交联密度和性能的关系

用核磁共振(NMR)法测定不同方法凝固天然橡胶的交联密度,研究其与性能之间的关系。结果表明,硫化胶的交联密度不仅影响其核磁共振的横向弛豫时间(T1),而且影响其纵向弛豫时间(T2)。随着交联密度大,硫化胶的核磁共振弛豫时间缩短。另外,微生物凝固天然橡胶硫化胶的交联密度、正硫化时刻扭矩和拉伸强度均大于酸凝固天然橡胶硫化胶的。     

微生物凝固天然橡胶交联密度的研究

采用核磁共振交联密度仪,考察了微生物凝固天然橡胶（NR-m）和酸凝固天然橡胶（NR-a）在硫化过程交联密度（XLD）、网链含量（AMc）、自由小分子含量（AT2）以及相邻交联点间的分子质量（Mc）的动态变化规律。研究结果表明,NR-m硫化胶的XLD比NR-a的高,NR-m硫化胶磁化曲线随时间衰减的速率比NR-a快,纵向松弛时间（T1）和横向驰豫时间（T2）比NR-a低,NR-m硫化胶网链部分的质量含量（AMc）明显高于NR-a的,而自由末端数则明显比NR-a的低。这表明微生物凝固法促进了天然橡胶的硫化作用,提高了硫化胶的交联密度。     

交联密度对丁腈橡胶阻尼性能的影响

测定了丁腈橡胶硫化胶的交联密度和阻尼性能，考察交联密度对阻尼性能的影响。结果表明，交联密度是阻尼性能的重要影响因素。交联密度的增加可以提高丁腈橡胶的损耗峰所对应的温度并使储能模量E＇的转变区域向高温方向移动，但交联密度过高会导致有效损耗温度区域缩小。     

交联密度对天然橡胶动态性能的影响

研究了交联密度对分别用炭黑和白炭黑补强的天然橡胶硫化胶动态力学性能、压缩屈挠性能的影响。结果表明：提高交联密度可以降低炭黑或白炭黑补强的天然橡胶硫化胶的损耗因子,减少压缩屈挠生热,提高橡胶材料的耐疲劳性能。     

提高丁腈手套交联密度的研究

一次性丁腈手套是医疗消耗品,由于其不易致过敏,良好耐溶剂性以及穿戴舒适性越来越受市场欢迎.本文以交联密度作为主要评价指标,研究了二正丁基二硫代氨基甲酸锌(BZ)和二乙基二硫代氨基甲酸锌(EZ)单独使用以及并用时对硫化胶的交联密度的影响;探讨了硫化温度以及硫化时间对交联密度的影响.结果表明在硫化工艺不变的条件增加促进剂的...     

硅橡胶交联密度测定方法的对比研究

对比研究平衡溶胀法和平衡模量法测定硅橡胶的交联密度。结果表明:两种方法测定的硅橡胶交联点间平均相对分子质量和交联密度稍有不同;平衡溶胀法结果重复性和精密度高,但耗时较长,平衡模量法耗时少、快速,适合大批量样品测试,但精密度稍差;平衡溶胀法更适用于区分不同批次硅橡胶之间交联密度的差别。     

核磁共振法研究炭黑/白炭黑并用比对胶料交联密度的影响

用核磁共振（NMR）法（仪器为NMR法交联密度测试仪）研究炭黑/白炭黑并用比对胶料交联密度的影响。结果表明：NMR法测试胶料交联密度,可反映炭黑和白炭黑与橡胶的作用;采用NMR法试测试的胶料交联密度对炭黑/白炭黑并用比变化敏感;炭黑用量增大,硫化胶的交联密度增大;偶联剂Si75能减少白炭黑与炭黑之间的作用,促进白炭黑分散,消除和减轻白炭黑用量较大导致的胶料硫化延迟。     

橡胶交联密度测试方法及其应用研究进展

介绍橡胶交联密度的测试方法及其应用研究进展。橡胶交联密度的测试方法主要包括化学法、平衡溶胀法、核磁共振法、应力-应变法和原子力显微镜法,其中核磁共振法具有广阔的应用前景。交联密度的测定结果可以表征硫化胶交联程度,用于研究硫化和补强体系及硫化工艺对硫化胶物理性能的影响;老化过程中交联密度的测定可以表征硫化胶耐老化性能,研究配方组分及老化条件对硫化胶性能的影响。今后应加强橡胶交联密度测定方法的规范化和标准化,提高测定结果的可靠性。     

硅烷用量对白炭黑填充胶料交联密度的影响

该文描述了硫化过程中添加的游离硫黄在白炭黑-橡胶结合与基质交联间的优劣比较,对含硫官能硅烷偶联剂Si69及Si266的变量进行了两种统计性试验。可以看出,一方面硅烷用量的增加增强了白炭黑-橡胶结合,引起模量提高并有效降低拉断伸长率;另一方面,白炭黑-橡胶结合消耗游离硫黄产生低基质交联密度。由于两种交联反应同时发生,基质和白炭黑-橡胶网状结构之比不能随意变化。为了获得最佳补强效果并满足性能要求,已精确地对硅烷与硫黄的比率进行了调整。该研究的目的旨在深入了解白炭黑填充胶料的补强效果,并对指导怎样使胶料拥有最佳产品性能有很大意义。     

Radiation degradation of epoxidized natural rubber studied by solid‐state nuclear magnetic resonance and infrared spectroscopy

The mechanism of radiation‐induced structural changes in epoxidized natural rubber was investigated using nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopy. Samples were irradiated both under vacuum and in air. Because the rubbers crosslinked during irradiation, solid‐state NMR had to be used. The cross polarized/magic angle spinning NMR spectra were used to calculate the radiation yields. Ring opening of the epoxy groups was found to occur during irradiation. Most of the crosslinking was due to epoxy group ring opening, and very little or no C C crosslinking was observed. © 2000 Society of Chemical Industry     

红外和核磁共振法鉴定聚醚型聚酯的组成结构

利用红外吸收光谱及核磁共振波谱仪的一维和二维技术对一种未知聚合物试样进行鉴定。由核磁共振二维技术分析得出聚醚酯的序列结构及其分布。结果表明:该未知聚合物试样为聚醚酯弹性体,由对苯二甲酸、间苯二甲酸、新戊二醇、乙二醇、聚四氢呋喃醚共聚而成。     

Chemical structure of bitumen-derived asphaltenes by nuclear magnetic resonance spectroscopy and X-ray diffractometry

Asphaltene samples obtained from bitumen processed at three Indian refineries were characterized for chemical composition and structure by nuclear magnetic resonance (n.m.r.) spectroscopy and X-ray diffractometry (XRD). The average structural parameters were obtained by combined ¹H, ¹³C and DEPT spectral editing techniques. New equations were used for the estimation of n.m.r. average structure parameters. The macrostructure and crystalline parameters of these samples were obtained by XRD. A combined n.m.r. and XRD procedure was used to estimate the size of the average aromatic structural unit. Asphaltenes from one of the bitumens (ASP-D) was found to have different structural parameters from those of the asphaltenes from the other two bitumens. The number of aromatic rings per unit sheet in ASP-D was eight, compared with 13 for both ASP-M and ASP-H. XRD data indicated that the aromatic sheets are randomly oriented in ASP-D. The structural parameters allowed a model structure of the asphaltenes to be constructed.     

The structure determination of leucoanthraquinones by proton and carbon-13 nuclear magnetic resonance spectroscopy

Leucoquinizarin reacts with amines to give mono- and diaminoanthraquinones. Since contamination by diaminoanthraquinones greatly influences the quality of monoaminoanthraquinones as dyestuffs (and vice versa), it is important to elucidate the structure of leucoanthraquinones in connection with the reactivity and selectivity of the reaction with amines. The structure of the leuco compound of 1,4-bis(butylamino)anthraquinone was assigned to be 1,4-dibutylamino-2,3-dihydroanthracene-9,10-dione by p.m.r. However, the structure of the leuco compounds of 1,4-dihydroxyanthraquinone(quinizarin) and 1-butylamino-4-hydroxyanthraquinone could not be determined definitely by p.m.r. alone. An examination of ¹³C-n.m.r. spectra of anthraquinones and leucoanthraquinones afforded convincing data. The structures of the leuco compounds of quinizarin and 1-butylamino-4-hydroxyanthraquinone were concluded to be 9,10-dihydroxy-2,3-dihydroanthracene-1,4-dione and 1-butylamino-10-hydroxy-2,3-dihydroanthracene-4,9-dione respectively. The reactive species of leucoquinizarin are discussed on the basis of the results.     

Characterization of Canadian coals by nuclear magnetic resonance spectroscopy

Apparent aromaticities of a series of Canadian coals of different rank were estimated by solid state nuclear magnetic resonance spectroscopy. The aromaticities varied from 0.57 for a lignite up to 0.86 for a semi-anthracite coal. The aromaticities correlated well with fixed carbon and oxygen content of the coals as well as with the mean reflectance of the coals. Correlations were also established between aromaticities and the H/C and H_aru/C_ar ratios of the coals. Uncertainties in calculation of the hypothetical H_aru/C_ar ratios, from experimental data were pointed out.Structural parameters of the chars derived from the coals by pyrolysis at 535°C were, also, estimated. The H/C and H_aru/C_ar ratios of the chars were markedly lower than those of coals. This was complemented by higher apparent aromaticities of the chars compared with the coals.     

改性Kevlar纳米纤维对天然橡胶耐溶剂性能和交联密度的影响（英文）

制备了改性Kevlar纳米纤维(m-KNFs)填充天然橡胶硫化胶,研究了不同用量的m-KNFs对天然橡胶耐溶剂性能和交联密度的影响。结果表明,m-KNFs可有效增强天然橡胶的耐溶剂性能,当m-KNFs的用量为7份时,天然橡胶的溶剂吸附常数比未填充时降低了11. 7%。同时,天然橡胶的交联密度随着m-KNFs用量的增加而增大。     

The study of natural epoxy oils and epoxidized vegetable oils by13C nuclear magnetic resonance spectroscopy

The¹³C nuclear magnetic resonance spectra ofVernonia galamensis seed oil and of epoxidized palm super olein, soybean oil and linseed oil have been recorded and interpreted. The chemical shifts of the major signals are assigned and semi-quantitative results are derived. The spectroscopic procedure provides a useful method of analyzing oils that contain epoxy acids. The epoxide function differs from a double bond in its influence on the chemical shifts of nearby carbon atoms.     

Analysis of asphaltenes by carbon and proton nuclear magnetic resonance spectroscopy

Proton and ¹³C nuclear magnetic resonance spectroscopy has been used to derive a series of parameters of an ‘average molecule’ which characterize complex multicomponent organic mixtures such as asphaltenes. The method developed here is based on a minimum of assumptions and takes explicitly into account the effects of the oxygen atoms on the chemical shift of the adjacent ¹³C atoms. Moreover, the integrated intensities characterizing ring junction or substituted and unsubstituted carbon atoms are no longer determined on a chemical shift basis but are calculated by using parameters extracted from ¹H and ¹³C spectra. Factors influencing quantitative ¹³C measurements on asphaltenes in the Fourier transform mode are briefly discussed. The variations of parameters such as the aromaticity factor, the degree of substitution, and the number of aromatic and naphthenic cycles per structural unit are studied as functions of depth of burial for rock samples from the Toarcian Paris basin.