Effects of mechanical interactions on the hydrostatic stress in randomly distributed rubber particles in an amorphous polymer matrix

The equivalent inclusion method (EIM) assuming linear elasticity is used to calculate the mechanical interactions between spherical rubber particles in an amorphous matrix, as in a rubber toughened polymer. The influences of the various calculation parameters are examined and it is shown that the method can provide reliable results with regard to the level of hydrostatic stress in the particles. Damage of the material is simulated by replacing the most stressed particles by voids. Numerical simulations for several hundreds of interacting particles give information on the kinetics and spatial organisation of the damage. It appears that, as the volume fraction of particles increases from 10 to 20%, the spatial configuration of the damage evolves from a localised to a diffuse mode. These results are discussed in relation to the efficiency of rubber toughening.     

一起氧气瓶燃割事故分析

20 0 2年 5月 30日晚 7:5 5 ,徐州市工程集团某机械厂下料车间 ,氧气汇流排中一只即将开启使用的氧气瓶发生燃烧击穿事故 ,造成一死一伤的严重后果。事故发生的第二天笔者被特邀赶到现场 ,会同调查组对事故的性质、原因进行分析鉴定 ,并通过了原因分析鉴定结论。为防止此类事故的再次发生 ,引起充装或使用单位的足够重视 ,从中吸取教训 ,把事故消灭在萌芽状态 ,减少不必要的损失 ,现将这起氧气瓶燃割事故介绍如下。1　钢瓶及汇流排的原始情况钢瓶为河北涿鹿高压气瓶制造厂生产 ,气瓶原始数据如下 :气瓶编号 0 85 15 ,水压试验TP2 2 5 ,工…     

充油SEBS的结构、力学性能和紫外辐照稳定性

自制了一种中间基的苯乙烯-乙烯/丁烯-苯乙烯三嵌段共聚物(SEBS)弹性体用填充油,并从分子结构及微相结构上分析了线型和星型SEBS充油体系的力学性能、紫外辐照稳定性与其结构的关系。通过小角X射线散射(SAXS)、透射电子显微镜(TEM)表征了SEBS充油体系的微观结构,揭示了SEBS分子结构是影响充油体系微观结构的主要因素,且软硬段电子密度差以及PS相间距越大,SEBS的微相分离程度越高。结合Instron万能材料试验机的测试结果,发现SEBS微相分离程度高有利于充油体系力学性能的提高。通过傅里叶红外光谱(FTIR)研究了经紫外辐照后SEBS体系的化学结构变化,结果显示,经紫外辐照后的体系均在1700~1740 cm-1、1800 cm-1附近出现吸收峰,且吸收峰强度越大,力学性能下降得越快,表明氧化降解是造成SEBS体系力学性能下降的主要因素。     

氯丁橡胶胶粘剂

1低温聚合、快速结晶型氯了用胶氯丁橡胶的结晶度与反式1，4含量有关，而反式1，4含量又是由乳液聚合温度决定的，聚合温度越低，反式1，4含量越高。为了得到快速结晶型氯丁橡胶，聚合必须在较低温度下进行，一般不高于15℃。快速结晶型氯丁橡胶广泛用于鞋底的粘接、层压板的粘合、汽车装饰，以及其它多种用途。主要从引发剂、调节剂等几个方面改进氯丁橡胶的性能：2＠基氯T橡胶。驻基氯丁胶是氯丁二烯和甲基丙烯酸的共聚物，是非结晶性，适用于室温硫化和耐热性用途。与快结晶型氯丁橡胶相比，由其配制的胶粘剂粘结强度形成更快，耐热性增…     

橡胶硫化促进剂NS的合成研究

本研究采用促进剂M、叔丁胺为原料,以过氧化氢为氧化剂,用水做溶剂在酸性条件下合成橡胶硫化促进剂NS。并通过实验得到优化工艺条件:n(叔丁胺)/n(促进剂M)为2.0、n(过氧化氢)/n(促进剂M)为1.5、反应温度为60℃和反应时间为90min,在此工艺条件下合成橡胶硫化促进剂NS的收率可达90.0%。     

ADHESION OF ELASTOMERS: DWELL TIME EFFECTS

The strength of adhesion of elastomers to rigid substrates generally increases with time of contact. This effect has been studied for samples of butyl and chlorobutyl rubber adhering to some rigid substrates. The peel strength increased continuously over long periods of contact until in some cases failure became cohesive within the elastomer layer. At higher temperatures the strength increased more rapidly, consistent with the WLF relation governing molecular motions. It is postulated that slow molecular rearrangements occur at the interface and increase the bond strength. A criterion for the observed transition from interfacial to cohesive failure is suggested.     

Effects of primary and quaternary amine intercalants on the organoclay dispersion in a sulfur-cured EPDM rubber

The effects of primary and quaternary amine modified montmorillonite (MMT) on the nanocomposite formation in an ethylene/propylene/diene rubber (EPDM) were studied. The organoclay was introduced in 10 parts per 100 rubber (phr) amount in the related recipes. X-ray diffraction spectra (XRD) were recorded in various stages of their processing in order to get information about the intercalation process. The curatives found to play a crucial role, as they promote the intercalation/exfoliation phenomena. Incorporation of MMT modified with octadecylamine (MMT-PRIM) in the EPDM and its more polar version (contains maleic anhydride grafted EPDM, EPDM-MA) resulted in intercalated and exfoliated structures, respectively. Deintercalation of the clay (collapse of the layers), generated in both EPDM and EPDM-MA during vulcanization, was attributed to the reactivity of the PRIM and to its ability to participate in complex formation with the curatives (vulcanization intermediates). This explanation was supported by the non-collapse of the MMT layers when the less reactive modifier, viz. octadecyltrimethylamine served as MMT intercalant (MMT-QUAT). In the latter case the corresponding nanocomposite contained mostly intercalated clay layers based on XRD and transmission electron microscopic (TEM) results.     

Catalytic characteristics of various rubber-reinforcing carbon blacks in decomposition of methane for hydrogen production

Carbon black has recently been reported to act as an effective catalyst for methane decomposition and to exhibit stable catalytic behavior despite carbon deposition, and thus it can be used for CO₂-free production of hydrogen from natural gas. In this work, various carbon blacks with different primary particle size were investigated with respect to methane decomposition under atmospheric pressure from 1123 to 1223 K. Catalytic characteristics, such as activity, activation energy and reaction order, were investigated and compared. It was observed that with decreasing primary particle size (or increasing specific surface area), the specific activity increased and the activation energy decreased. The reaction orders for various pelletized, rubber-reinforcing carbon blacks were 0.6–0.7, about the same regardless of the primary particle size, while they were near 1 for fluffy carbon blacks. Fluffy carbon black showed higher activity and activation energy than the pelletized carbon black of the same primary particle size. Changes of the surface morphology during carbon deposition were observed by TEM. Variations of the number of active sites were discussed in regard of the primary particle size, carbon deposition and binder. The presence of different types of active sites was also suggested.     

原料及配方对单组分聚氨酯胶粘剂性能的影响

以不同性质的聚醚多元醇（210，220，330，3050）、TD1－80等为主要原料，分别采用一步法和预聚物法合成单组分聚氨酯胶粘剂，并用该胶粘结橡胶粉压制成铺垫材料。研究了不同多元醇、各多元醇的不同配比、合成工艺及不同异氰酸酯指数等因素对橡胶粉粘接料（以下简称粘接料）的影响。结果表明：以220和3050的1：1混合物，TDI为主要原料，用预聚物法合成的游离NCO含量为5％的单组分聚氨酯，其拉伸强度、扯断伸长率、耐水性、耐热性等均能满足橡胶粉粘结料的性能要求。     

PVC和白炭黑对NBR／PVC共混体耐磨和耐疲劳性的作用

研究了ＰＶＣ和白炭和黑对热力学不相容的ＮＢＲ／ＰＶＣ并有耐磨和耐疲劳性的影响，并探讨了其相应机理，借助扫描电镜（ＳＥＭ）观察了并用体系的屈挠疲劳断面，发现随ＰＶＣ用量增加和白炭黑用量减少，疲劳断面由原来的粗糙孔洞（Ｃｏａｒｓｅ－ｈｏｌｅ）裂纹型变成了波浪河流（Ｗａｖｅ－ｒｉｖｅｒ）型，并用体系优异的耐磨和耐疲劳性是由其相容性和界面过渡层结构等决定的。