多功能稀土促进剂(La-GDTC)的制备及其硫化性能研究

通过谷氨酸、二硫化碳和氯化镧合成了一种新型的多功能硫化促进剂——谷氨酸二硫代氨基甲酸镧(La-GDTC),利用紫外-可见吸收光谱、核磁共振13C谱、元素分析、红外光谱(FTIR)和X射线光电子能谱(XPS)等分析手段证实了La-GDTC中的二硫代氨基甲酸根和羧酸根与镧离子形成了配位络合结构。通过研究SBR/La-GDTC混炼胶的硫化性能,结果显示随着La-GDTC加入量的增多,SBR/La-GDTC混炼胶的正硫化时间(tc90)从17.23 min减少至12.47 min,证实了La-GDTC的加入能够很好地促进橡胶的硫化,这与SBR/La-GDTC混炼胶的活化能计算结果是一致的。     

不同硫化体系天然橡胶复合材料力学性能的影响

研究了不同硫化体系对炭黑填充天然橡胶力学性能的影响。结果表明,以N-(氧化二亚乙基)-2-苯并噻唑次磺酰胺(NOBS)为主促进剂的四种硫化体系中,半有效硫化体系硫化的橡胶的综合性能最好。在以N-环己基-2-苯骈噻唑次磺酰胺(CBS)+2-硫醇基苯骈噻唑(M)为促进剂的四种硫化体系中,用普通硫化体系(CV)硫化得到的碳黑/天然橡胶的综合性能最优。本文还研究了不同硫化体系对炭黑/碳纳米管填充天然橡胶力学性能的影响,结果表明,普通硫化体系(CV)硫化得到的碳纳米管/碳黑/天然橡胶的综合性能最优。     

二乙基二硫代氨基甲酸镧在丁腈橡胶中的应用研究

以LaCl_3·7H_2O及二乙基二硫代氨基甲酸钠为原料合成了二乙基二硫代氨基甲酸镧配合物(LaDC),并将其作为硫化促进剂加入丁腈橡胶(NBR)中,考察了LaDC/NBR混炼胶硫化特性,同时与二硫代氨基甲酸锌、二硫代氨基甲酸钠进行对比,发现LaDC对NBR有着良好的硫化促进效果,并且其中的稀土起到延长焦烧时间的作用;进一步在不添加活性剂的情况下,将其在不同牌号的丁苯橡胶、丁腈橡胶中的促进效果进行比较,发现LaDC对极性橡胶NBR仍然可发挥良好的硫化促进作用,这可能与NBR具有极性官能团有关。进一步将其应用于炭黑N330填充的丁腈橡胶(NBR)中,对比了添加LaDC和同时添加促进剂DM与抗氧剂BHT硫化胶的综合物理机械性能,结果发现, LaDC在NBR中可表现出硫化速率快、扭矩高的特点,物理机械性能和老化性能与后者基本相当。LaDC在NBR基体中可发挥一剂多能的效果,有望成为一种新型多功能橡胶助剂。     

橡胶胶乳的硫化——Ⅰ.胶乳硫化基本规律的初步探讨

本文系统地研究了胶乳种类、胶乳浓度、硫化温度、硫磺用量以及促进剂用量等五个主要因素对天然胶乳硫化过程的影响,并且阐明了在硫化过程中胶乳胶膜物理性能、结合硫量以及橡胶交联度之间的相互关系。 实验结果说明,胶乳中非橡胶成分在硫化初期不仅不促进硫化而且还阻碍硫化进程,在硫化的中期与后期它的促进效果才明显地显示出来。非橡胶成分含量愈高其硫化胶乳胶膜物理性能愈低。在一定范围内随着胶乳浓度的降低硫化速度稍有增加。随着硫化温度的升高胶乳硫化速度将相应加速,但在我们使用的硫化体系条件下温度过低与过高时其对硫化速度的影响减弱,最适宜的硫化温度是60—70℃。硫磺用量增加到一定程度后它对胶乳硫化速度即不再产生影响,在胶乳硫化过程中所能达到的结合硫量远远低于硫磺在橡胶中的溶解度。在通常用量下促进剂S.D.C.用量愈大其硫化促进效果亦愈大,在用量为0.125—0.25％之间其促进效果有一明显的转折。 硫化胶乳胶膜性能与橡胶交联度及结合硫量之间有一定的依赖关系。各种不同的影响胶乳硫化的因素都不改变这一依赖关系。在胶乳硫化过程中硫磺的交联效率是不恒定的,胶乳在硫化时主要是形成多硫键。在胶乳硫化时结合硫磺中的相当一部分并不对交联键的形成作出贡献。 胶乳硫化动力学基本     

2-巯基苯并噻唑稀土配合物的合成、表征及橡胶硫化促进性能研究

在无水乙醇溶剂中,以稀土氯化物与2-巯基苯并噻唑钠盐反应,合成了8种稀土含硫有机配合物.通过元素分析、红外光谱和热重分析,确定了配合物的组成为RELCl2*RE(OH)3*xH2O(L=2-巯基苯并噻唑, RE= La～Gd, Y, 除Pm外,x=0,2～4 );并对合成的镧配合物进行了橡胶硫化促进性能研究,结果表明,该类配合物具有较好的硫化促进性能和改善硫化胶物理机械性能的特性.     

纳米二氧化硅填充辐射硫化三元乙丙橡胶

用辐射硫化法替代传统硫化法,并以纳米二氧化硅为填料成功制备了纳米填充型三元乙丙橡胶密封材料。研究结果表明,纳米二氧化硅对辐射硫化三元乙丙橡胶有明显的补强效果,其最佳用量为40phr;吸收剂量超过20kGy后,橡胶总体性能下降;硫化胶的凝胶含量随填料含量的增加而增加,且凝胶含量的增大有利于提高辐射硫化胶的性能。对所得辐射硫化胶的透气透水性进行测试,数据显示与传统硫化法相比,辐射硫化法制备的橡胶其透气率和透水率均明显下降,表明材料的密封性较好。     

促进剂1,5-亚戊基二硫代氨基甲酸锌赋予天然橡胶的交联结构及均化应力作用

以1,5-亚戊基二硫代氨基甲酸锌(ZPDC)为促进剂,对天然橡胶(NR)的交联结构和均化应力作用进行研究。研究发现,促进剂ZPDC配合NR的硫化胶交联键以多硫键为主,对比于同类促进剂二正丁基二硫代氨基甲酸锌(BZ)具有更高含量的多硫键,赋予橡胶更好的均化应力作用,主要表现在抗撕裂性能的显著提升。此外,通过对NR配合促进剂ZPDC的硫化历程和力学性能的分析研究,发现适宜的硫化温度条件为120～130℃,用量为1.5～2.0 phr,硫化胶表现出最好的均化应力作用。     

聚丙烯／顺丁橡胶动态硫化增韧的研究

研究了在聚丙烯(pp)与顺丁橡胶(BR)共混过程中加入橡胶硫化剂使共混体系中橡胶相动态硫化交联。研究结果表明,采用动态硫化法可提高共混物的冲击强度和拉伸强度。借助于SEM和DMA,证实了动态硫化使PP/BR共混体系具有相界面粘结良好的多相结构,改善了两相相容性。探讨了动态硫化增韧的机理。     

N-叔丁基-2-苯并噻唑次磺酰胺的合成工艺研究进展

N-叔丁基-2-苯并噻唑次磺酰胺(TBBS)是一种重要的橡胶硫化促进剂,生产量和应用范围不断扩大.综述了近年来TBBS的合成工艺,包括次氯酸钠氧化法、催化氧化法、双氧水氧化法、电解氧化法和氯气氧化法等,对其工艺路线的优缺点进行了总结比较,并简要介绍了TBBS的国内外生产及市场开发情况.     

杜仲胶研究新进展

本文从和天然橡胶对比开始,对杜仲胶作了简要介绍;根据杜仲胶链结构的三大特征:双键,柔性及反式链结构,及其在橡胶一塑料材料谱中的特殊位置,对杜仲胶结构与性能的关系进行了讨论,作者指出:由于杜仲胶硫化过程三阶段特征的揭示,而通过与橡胶,塑料进行多途径共混,又可获得广性能的材料,从而使杜仲胶研究进入材料工程学新阶段。文中用图示描述了杜仲胶硫化弹性网络的非无规线团模型,并指出:其弹性来自分布于整个网络中各交联点的备向同性构象记忆。     

Radiation Vulcanization of Magnetorheological Elastomers Based on Silicone Rubber

The fabrication of magnetorheological （MR） elastomers was studied by two vulcanization methods, including heat vulcanization （HV） and radiation vulcanization （RV）, were employed to fabricate MRE samples. The dynamical mechanical properties were characterized by using a dynamic mechanic analyzer. In particular, both the MR effect and its durability were investigated. The experimental results showed that RV samples have large magnetoinduced modulus, large zero-field modulus, and good durability property of MR effect. To explain these results, cubic deformation and plasticizer migration were analyzed. Large magneto-induced modulus of RV sample results from cubic deformation during vulcanization process. And the plasticizer migration results in better durability of MR effect.     

The mechanical properties of radiation-vulcanized NR/BR blending system

The effect of radiation dose on the mechanical properties of NR/BR blending system is reported in this paper. A comparison was made between sulphur vulcanization and radiation vulcanization for an optimal nature rubber (NR)/ butyl rubber (BR) blending ratio (60/40) at dose range from 10 to 150 kGy. The result shows that the mechanical properties, especially, tensile strength, elongation at break, and tear strength have been improved significantly by radiation–vulcanization. This finding was also proved by thermal aging experiment on a selected NR/BR blend at 70°C for up to 168 h.     

The sulfur reversion process in natural rubber in terms of crosslink density and crosslink density distribution

Unfilled natural rubber compounds composed of conventional (CV), semi-efficient (SEV), efficient (EV) and sulfur donor (SD) vulcanization systems were heat aged to promote sulfur reversion. Rheometry, hardness, strain-strain characteristics including Mooney-Rivlin analysis, equilibrium solvent swell and Double Quantum (DQ) Nuclear Magnetic Resonance (NMR) were used to monitor crosslink density changes. A loss of crosslink density was observed by rheometry, C₁, equilibrium swelling and by DQ NMR as a function of cure extent. No chain scission reactions were operating in the time/temperature conditions used. All crosslink distributions were unimodal and the network homogeneity followed the order of EV > SD > SEV > CV. The crosslink distribution narrowed during the curing process for the CV and SEV systems. Non-oxidative maturation reactions were advantageous in promoting a more random distribution of crosslinks in the polymer matrix.     

顺丁橡胶／低密度聚乙烯的共混

比较了未交联和动态交联不同组成PB/LDPE共混物的力学性能。共混物的T_g、T_m和T_d不随组成而变化,表明PB和LDPE不具有相容性。但共混物中PE的γ转变向高温方向位移,说明PE非晶部分的分子短链和PB有界面相互作用。形态研究表明,未交联体系中量多的组份形成连续相,动态交联体系在PB/LDPE≤70/30时,PE呈连续相,交联的PB为分散相。     

Morphology and properties of super-toughened bio-based poly(lactic acid)/poly(ethylene-co-vinyl acetate) blends by peroxide-induced dynamic vulcanization and interfacial compatibilization

Super-toughened poly(lactic acid) (PLA)/poly(ethylene-co-vinyl acetate) (EVA) blends were prepared via 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (AD) induced dynamic vulcanization and in situ interfacial compatibilization. The effects of AD on the morphology and properties of PLA/EVA blends were studied using a Brabender torque rheometer, gel content test, scanning electron microscopy (SEM), differential scanning calorimetry (DSC) thermogravimetric analysis (TGA) and mechanical properties test. The torque and gel content demonstrated that EVA and PLA was successfully vulcanized in the presence of free radicals obtained by the decomposition of the 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (AD). Additionally, the gel content results indicated that, compared with PLA, EVA is more aggressive with free radicals. The SEM revealed that a relatively uniform phase morphology and good interfacial compatibilization were achieved in the dynamically vulcanized PLA/EVA/AD blends. The interfacial reaction and compatibilization between the component polymers resulted in the formation of super-toughened PLA/EVA blended materials.     

Crosslink network evolution of BIIR/EPDM blends during peroxide vulcanization

Crosslink network evolution of brominated butyl rubber (BIIR)/ethylene–propylene–diene-monomer rubber (EPDM) blends during peroxide vulcanization is studied at a meso-scale level. In this work, EPDM is added as a co-agent to increase the crosslink density of BIIR vulcanization. With increasing EPDM content from 0 to 20 phr, the maximum torque of BIIR/EPDM compounds during vulcanization increases by 73%, reaching to 3.40 dNm. Vulcanization kinetic study shows that addition of EPDM favors to the crosslinking of BIIR compound. Meanwhile, the addition of 20 phr EPDM contributes to an increase in the crosslink density of BIIR/EPDM(80/20) vulcanizate, avoiding downward trend at post-cure period in comparison with BIIR only. Crosslink network evolution of BIIR/EPDM blends is divided into three periods during peroxide vulcanization at 150 °C. The role of EPDM in the crosslink network evolution is studied by proton nuclear magnetic resonance, and a “network patching” mechanism is proposed in which EPDM is implied to work as patch on damaged crosslink network resulted from the degradation nature of BIIR.     

Thermal Properties of N-ethyl-N-phenyl-Dithiocarbamates and Their Influence on the Kinetics of Cure

The thermal properties (in the temperature range of 100–250°C) of N-ethyl-N-phenyldithiocarbamatecomplexes of Zn(II), Co(III), Ni(II), Cu(II) and Pb(II) and their influence on the kinetics of cure have been studied by differential scanning calorimetry (in nitrogen). It was found that Zn(II), Co(III) and Pb(II) dithiocarbamates melted without further effects, while the melting of Ni(II) and Cu(II) dithiocarbamates is accompanied with decomposition. From the kinetic point of view, the dithiocarbamates decrease the values of the reaction order and the values of rate constants follow this order (with respect to the metal ion): Zn(II)<Cu(II)<Pb(II)<Ni(II)<Co(III).This revised version was published online in November 2005 with corrections to the Cover Date.     

Micromechanical models of young's modulus of NR/organoclay nanocomposites

Small strain Young's moduli of natural rubber (NR)/organoclay nanocomposites were estimated using the Guth–Gold, Halpin–Tsai (HT), and Krieger–Dougherty (KD) models, and compared with experimental measurements of NR vulcanizates containing organo‐montmorillonite (OM) or organo‐sepiolite (OS). To account for the effect on modulus of the NR matrix of the vulcanization‐active modifier in the organoclay, a matrix modulus correction (MMC) term was derived from the vulcanization parameters of the nanocomposites. The KD model gave a better empirical fit with the experimental data than the Guth–Gold model, with both giving good agreement with particle shape factors estimated from transmission electron microscope (TEM) images. The HT model gave the best fit with experiment for both types of nanocomposite, and use of the MMC term meant that the empirical shape factor was sufficiently close to that estimated from TEM images that the model could potentially be used to accurately predict the Young's moduli of NR/OM and NR/OS nanocomposites. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1621–1627, 2011