Studies on a new binary accelerator system containing TMTD and amidinothiourea in sulfur vulcanization of natural rubber

It is well known that the use of binary accelerator systems in rubber vulcanization provide better physical and chemical properties to the vulcanizates. The present work reports the results obtained on the study of amidinothiourea as a secondary accelerator along with tetramethyl thiuram disulfide (TMTD) in the sulfur vulcanization of natural rubber. Vulcanizates containing amidinothiourea have an appreciable increase in mechanical properties and better retention of these properties after aging compared to the reference mixes used. These mixes containing amidinothiourea showed appreciable reduction in optimum cure time as well. This suggests a nucleophilic reaction mechanism in the vulcanization reactions under review. Mixes with varying concentrations of amidinothiourea were tried; and the optimum level of amidinothiourea required has been derived based on the cure characteristics of the mixes and physical properties of the vulcanizates. © 1994 John Wiley & Sons, Inc.     

天然胶乳橡胶手套硫化问题的探讨

<正>一、引言胶乳硫化能充分改变或改善胶乳胶料性能,通常在胶乳配料时提高温度的情况下进行,硫化后的胶乳称为预硫化胶乳。胶乳硫化一般只适用于天然胶乳,是部分或完     

A kinetic model for sulfur accelerated vulcanization of a natural rubber compound

Vulcanization kinetics for a natural rubber compound were studied by a kinetic approach using the cure meter and DSC methods. A simplified but realistic model reaction scheme was used to simulate induction, curing, and overcure periods continuously. Physically significant parameters of the model were extracted from isothermal experimental data using a cure meter. The calculation demonstrated a good correspondence with isothermal cure meter data over the temperature range studied. The length of induction time, variation of maximum modulus with temperature, and the reversion phenomena observed from cure curves can be predicted. DSC data were found to be incompatible with the cure meter test, because the complex vulcanization reaction system is multiexothermal and it is difficult to isolate the heat due to crosslinking. Hence, the cure meter technique is suggested for the study of crosslink formation. The kinetic approach provides a way to incorporate vulcanization kinetics into simulation of reactive processing operations. © 1996 John Wiley & Sons, Inc.     

Radiation vulcanization of natural rubber latex with polyfunctional monomers

Natural rubber latex was irradiated with γ-rays from Co-60 in the presence of polyfunctional monomers to accelerate crosslinking of rubber molecules. Hydrophobic monomers were more effective in accelerating the vulcanization than were hydrophilic monomers. This was ascribed to high solubility of hydrophobic monomers in rubber particles. Among the hydrophobic monomers, neopentylglycol dimethacrylate (NPG) exhibited the highest efficiency in accelerating the vulcanization. Advantages of using NPG are (1) high colloidal stability of the irradiated latex and (2) high thermal stability of dried rubber film.     

Long-time sulfenamide-accelerated sulfur vulcanization of natural rubber/chlorobutyl rubber compounds

Sulfenamide-accelerated sulfur vulcanization of natural rubber/chlorobutyl rubber compounds has been investigated at temperatures from 155 to 175°C over 0.1 to 400 min. Continuous measurements in a Cone Rheometer were used to estimate the extent of crosslinking, which was plotted against cure time. On the basis of a kinetic analysis, two first-order vulcanization reactions, crosslinking and degradation, have been evaluated. Over the temperature range studied, there is no significant difference between the values of activation energy for these reactions. The rate of the degradation is slower by a factor of 20 than the rate of crosslinking. The degradation reaction can be limited by increasing the “efficiency” of the vulcanizing system.     

新型氟橡胶硫化剂

近年来,氟橡胶以其优异的耐热、耐油、耐溶剂、耐强氧化剂、阻燃等特性,以及良好的加工性能,越来越受到人们的重视,氟橡胶作为一种不可替代的高性能弹性体材料,不仅在需求上有了大幅度增加,而且其应用范围也正在不断扩大。氟橡胶的加工助剂也成为生产发展的一个重要环节,不少人     

Cure characteristics of unaccelerated sulfur vulcanization of epoxidized natural rubber

The curing characteristics of unaccelerated sulfur vulcanization of ENR 25 and ENR 50 were studied in the temperature range from 100–180°C. The range of sulfur loading was from 1.5 to 6.5 phr. The scorch time was determined by Mooney Shearing Disk Viscometer whereas the initial cure rate, maximum torque, and reversion properties were obtained from the Moving Die Rheometer (MDR 2000). Results shows that ENR 25 gives a longer scorch time than ENR 50, an observation similar to that in an accelerated system reported earlier. For temperature < 120°C, scorch time depends exponentially on sulfur loading for both rubbers. However, this dependence diminishes as temperature is increased. This observation is attributed to the availability of activated sulfur molecules for vulcanization. The initial cure rate and maximum torque increases with increasing sulfur loading. ENR 50, however, exhibits higher value than ENR 25, suggesting faster cure in the former. For a fixed sulfur loading, reversion is a time and temperature-dependent phenomenon. It decreases with increasing sulfur loading because of the increase of cross-linking density for both rubbers stuided. © 1996 John Wiley & Sons, Inc.     

Mechanism of radiation vulcanization of natural rubber latex sensitized by monoacrylates

The mechanism of radiation vulcanization of natural rubber with 2-ethyl hexyl acrylate (2EHA) monomer was investigated using electron spin resonance spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. The primary radicals formed in the arcylate molecule were found to abstract the allylic hydrogens of the polyisoprene. Crossliking may occur through the allylic radicals and/or main chain radicals formed on the polyacrylate. Acrylate was found to concentrate in the rigid regions of the crosslinked rubber indicating heterogeneity and a nonuniform distribution of the acrylate in the latex particles. The addition of the acrylate and the irradiation seems to effect the Brownian motion of the latex particles. Both the viscosity and the NMR peak widths are effected by the irradiation. Addition of 5% 2EHA increases the crosslinking by a factor of 3.6. The thermal stability of the rubber first increases with the dose in the presence of acrylate, but drops at higher doses due to peroxide formation. © 1995 John Wiley & Sons, Inc.     

挤出用溴化丁基橡胶硫化体系的研究

溴化丁基橡胶几种典型硫化体系的对比实验,结果表明,用氧化锌体系硫化的溴化丁基橡胶具有良好的焦烧安全性,比较适宜于挤出用;加入促进剂HVA-2,可显著提高胶料的硫化速度和交联程度,并改善焦烧安全性;当氧化锌用量为4份,HVA-2用量为1.5份时,胶料具有较佳的综合物理性能和加工安全性。     

Effect of temperature on sulfur prevulcanization of natural rubber latex

Sulfur prevulcanization of natural rubber latex was conducted at 60, 70, 80, and 90°C for different periods. The extent of crosslinking was assessed. Tensile properties, water absorption, leaching, and stress-relaxation characteristics of the films were also evaluated. The volume fraction of rubber (Vr), which is a measure of crosslink density of the films, showed a maximum when prevulcanization was conducted at 80°C for 2 h or at 90°C for 1 h. At lower temperatures, the rate of reaction was slow. At each temperature, tensile strength and elongation at break decreased when the prevulcanization time increased, whereas the modulus increased up to a maximum crosslinking and thereafter decreased. Water absorption and leaching were more rapid in prevulcanized film than in postvulcanized film. The rate of stress relaxation slightly increased as the extent of prevulcanization increased. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 1913–1920, 1997     

氯丁橡胶用快速硫化体系

该文研究了氯丁橡胶用快速硫化体系。结果表明,以4份氧化镁、5份氧化锌、1．5份TMU、0．5份TMTD、0．5份CZ为W型氯丁橡胶的硫化体系,可使胶料具备焦烧时间长、硫化速率快的特点,硫化胶的综合性能较好。     

硫化体系对天然橡胶性能的影响

采用常规硫化体系(CV)、半有效硫化体系(SEV)和有效硫化体系(EV)制备了不同的NR(天然橡胶)硫化胶。着重探讨了不同硫化胶的微观形貌、200%定伸强度、撕裂强度、拉伸强度、断裂伸长率和交联密度。研究结果表明:SEV硫化胶的微观形貌相对较好,填料能均匀分散在基体中;在其他条件保持不变的前提下,当w(NOBS)=w(硫)=2.0%(相对于NR质量而言)时,相应的未老化SEV硫化胶的撕裂强度(78 kN/m)相对最大;SEV硫化胶的交联密度大于CV硫化胶和EV硫化胶,并且适当增加交联密度能有效提高其综合性能,从而为开发新一代轮胎等复合材料奠定了基础。     

Structural characterization of vulcanizates. Part IX. Comparison of the vulcanization of natural rubber and cis-trans-isomerized natural rubber with sulfenamide-accelerated sulfur and dicumyl peroxide vulcanization systems

Large variations in the microstructure of 1,4-polyisoprenes, from ca. 100% cis-trialkylethylene groups, as in natural rubber (NR), to ca. 40% cis- and 60% trans-trialkylethylene groups, as in an equilibrium-isomerized NR, have little influence on the overall chemistry of vulcanization of the polyisoprenes by a N-cyclohexylbenzothiazole-2-sulfenamide-accelerated sulfur system or by a dicumyl peroxide system. The peroxide crosslinks the equilibrium-isomerized NR more efficiently than it crosslinks NR; this is attributed to the sulfur dioxide, which is used to isomerize the NR, scavenging some of the nonrubber constituents in the NR, which are known to compete with the rubber hydrocarbon for reaction with free radicals from the peroxide. By comparison with NR vulcanizates, the corresponding equilibrium-isomerized NR vulcanizates have higher values of the C₂ term of the Mooney-Rivlin stress–strain equation and higher χ (polymer–swelling liquid interaction parameter) values of the Flory-Huggins equation.     

天然橡胶硫化动力学研究

采用硫化仪测定了2种不同凝固工艺的天然橡胶（NR）的硫化过程,探讨了制胶工艺、配方和温度对硫化动力学参数的影响。研究结果发现,随着温度的上升,硫化速率常数迅速上升。在纯胶体系中,微生物凝固胶的活化能高于酸凝固胶。当加入炭黑后,酸凝固胶的活化能升高,而微生物凝固胶的活化能下降。     

无废水法生产橡胶硫化促进剂2-巯基苯并噻唑

以苯胺作为溶剂,对M(2-巯基苯并噻唑)进行结晶精制,可将粗M中的大部分胶体去除掉。设计了苯胺单程循环和多程循环2种流程,并分别给出结果数据。实验结果表明,精制后M的熔点可达到180℃以上,产品纯度高,无废水、废渣产生。该方法基本上能达到与酸碱处理相同的结果。     

橡胶硫化促进剂N-环己基-2-苯并噻唑次磺酰胺的团粒法造粒技术

采用团粒(聚)法制备了橡胶硫化促进剂N-环己基-2-苯并噻唑次磺酰胺(CBS)粒状产品,确定了团粒造粒工艺的最佳条件,并在此条件下进行了稳定运行实验.结果表明,用脱水后含水率为20%的CBS湿粉料为造粒原料,采用团粒法制备CBS粒状成品的最佳工艺条件:黏结剂乙烯-乙酸乙烯酯共聚物质量分数为CBS干基料的8%、湿粒含水率为34.77%,造粒盘倾角为35～45°、造粒盘转速为65 r/min,黏结剂乳液喷加时间约为10 min,造粒周期为50～60 min,烘箱干燥温度为(55±2) ℃,烘干时间为210 min;在最佳工艺条件下制得的粒状CBS性能均达到指标要求:初熔点不小于96.0 ℃,粒径为2.0～4.5 mm,粒子的平均强度在2.0～8.0 N,加热减量不大于1.00%,灰分不大于0.40%,成粒率超过60%.该粒状CBS能完全取代粉状产品,对橡胶的硫化性能无不良影响.     

天然胶乳的氢化

以水合肼、双氧水和硼酸为催化体系,对天然胶乳进行非贵金属催化的原位母体加氢.并用核磁共振氢谱对氢化天然胶乳的结构进行表征.结果表明,氢化度随着硼酸用量的增加而增大,当硼酸/碳碳双键(摩尔比)达到0.25时,天然胶乳的加氢度接近60%;     

新型橡塑硫化助剂的合成

以九水硫化钠、硫粉、γ-氯丙基三乙氧基硅烷为原料,甲苯、乙醇作溶剂,合成了双-(γ-三乙氧基硅丙基)二硫化物。讨论了反应物比例、溶剂用量、反应温度和时间等因素对产率的影响。结果表明,最佳工艺条件:硫与九水硫化钠的物质的量比为1.05:1,甲苯与九水硫化钠的物质的量比为36:1,γ-氯丙基三乙氧基硅烷与过硫化钠的物质的量比为2.1:1,无水乙醇与过硫化钠的物质的量比为5.0:1,反应温度为80℃,反应时间为4 h。最终制得的产品外观为淡黄色,类乙醇香味,产率为95.63%,含硫量达13.8%,产品贮存时间长。     

橡胶硫化促进剂DZ生产废水的预处理实验研究

采用Fenton氧化法对橡胶硫化促进剂生产废水进行预处理,考察了酸析法以及H_2O_2投加量、Fe⁽²⁺⁾投加量、pH值、反应时间对Fenton氧化法COD去除率的影响。结果表明,Fenton氧化法处理该废水的最佳反应条件为:pH值为3,H_2O_2投加量为55 mL/L,Fe(2+)投加量、pH值、反应时间对Fenton氧化法COD去除率的影响。结果表明,Fenton氧化法处理该废水的最佳反应条件为:pH值为3,H_2O_2投加量为55 mL/L,Fe⁽²⁺⁾投加量为2.8 g/L,反应时间为40 min。此时COD的去除率达82.91%。将酸析与Fenton氧化法联合后COD的去除率可达到85.78%,效果良好,为后续蒸发结晶分离氯化钠、硫酸钠奠定了基础。