On Mooney and Mooney stress relaxation. II. A nonlinear viscoelastic description: Experimental and numerical results

It has been investigated whether the stress build‐up and the stress relaxation involved in a Mooney test, with subsequent Mooney stress relaxation, can be described by nonlinear viscoelastic theory, more particularly the Wagner constitutive model. For this purpose, the viscoelastic behavior of three nonvulcanized EPDM materials, with similar Mooney viscosity but varying elasticity, has been studied. Relaxation time spectra were obtained from dynamic mechanical experiments, from which the step‐strain stress‐relaxation modulus was calculated. Stress build‐up experiments were performed with a cone and plate system in order to obtain the so‐called damping function (a measure for the deformation sensitivity) of the materials. Using these material functions, the Mooney test was successfully described with the Wagner constitutive model. Experimental and theoretical Mooney stress‐relaxation rates are in close agreement. The predicted Mooney viscosity is up to 25% lower than the measured value. This may be due to nonideal conditions during the Mooney test, such as inhomogeneous heating and secondary flows, and to inaccuracy of the damping function. The model calculations confirm the strong experimental dependence of Mooney measurements on small variations in instrumental conditions such as geometry, rotation speed, and so forth. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1220–1233, 1999     

Relations between high‐temperature mastication and Mooney viscosity relaxation in natural rubber

Mastication of natural rubber (NR) is undertaken as a preliminary step towards the preparation of NR‐based vulcanizates, a process during which the elastomer is broken down to a homogeneous matrix of lower viscosity. Several tests and indicators are in use for characterizing the behavior of elastomers but these have mostly been adopted for the nonmasticated product. This study uses coefficients generated from modeled Mooney relaxation data, as indicators of elasticity, to examine the effect of high‐temperature mastication on the processability of the masticated rubber. Some derived coefficients such as the terminal relaxation time (τ) from Maxwell's triexponential model, the elastic component (a) from Wu‐Abbott model [Y = 1 + a* ln(t) ? bt/(c + t)], and the constant (b) from the Power law model (Y = at^?b), adequately characterized the effect of mastication on NR. Although the NR grades studied were quite different with respect to their initial molar mass distributions, they followed a similar response to the mechanical models before and after mastication, indicating therefore that mastication decomposes to a similar extent, the various components (long isoprene chains, densely crosslinked solvent‐insoluble gel, etc.) that account for the viscoelastic behavior of the raw elastomer. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The Effects of High Styrene Resin on the Mooney Viscosity,Scorch Time,Cure Time and Physical Properties of Rubber Vulcanizates

Abstract

The effects of high styrene (HS) resin on the Mooney viscosity, scorch time, cure time and physical properties of rubber vulcanizates were evaluated. The Mooney viscosity decreased with increasing HS composition up to 20% after which it started to increase. The incorporation of HS was found to increase the scorch and cure times of the rubber vulcanizates. Physical properties i.e., hardness, tensile modulus (M 100) and resilience also increased with increasing HS composition. However the opposite trend was observed in the case of crosslink density.     

苯乙烯-丁二烯橡胶门尼黏度标准物质定值不确定度的评定

依照GB/T 1231.1-2000进行实验,利用JJF 1059-1999]对苯乙烯-丁二烯橡胶门尼黏度标准物质定值过程中的不确定度分量进行了分析和评定。该测定过程中所产生的不确定度主要由多家实验室测量重复性和定值样品均匀性、稳定性引入。定值样品苯乙烯-丁二烯橡胶SBR 1502的门尼黏度ML(1+4)100℃测量值49.1的不确定度为±0.8。     

苯乙烯-丁二烯橡胶门尼粘度比对结果评价

按照GB/T1232.1-2000,组织合成橡胶生产、加工、科研和质检的26家实验室进行了苯乙烯丁二烯橡胶门尼粘度数据比对,利用稳健统计技术对比对结果进行评价。所有参加比对的实验室反映了合成橡胶行业门尼粘度测试水平;国家、行业的质检机构显现了出较高的测试水平,科研开发的实验室测试水平有明显提高;生产、加工企业的实验室能够满足测试要求;参加比对的实验室测试水平总体比以往相比均有不同程度的提高。选择Z值较小且经过实验室认可的实验室作为门尼粘度标准物质研制定值单位。     

SIBR生胶门尼粘度对胶料性能的影响

研究不同门尼粘度的集成橡胶(SIBR)混炼胶和硫化胶的各项性能,并与溶聚丁苯橡胶(SSBR1204)进行对比.结果表明,适当提高SIBR生胶的门尼粘度,可以在不影响胶料加工性能的前提下,提高混炼胶强度,同时硫化胶的物理性能和动态力学性能也普遍得到改善.高门尼粘度的SIBR综合性能较理想,与SSBR1204相比并无显著差异.     

塑解剂DBD用量对胎面胶性能的影响

研究塑解剂DBD用量对胎面胶性能的影响.结果表明:在胎面胶中加入塑解剂DBD,胶料的门尼粘度减小,门尼焦烧时间和t90缩短;随着塑解剂DBD用量的增大,胶料的塑性稳定性增大,炭黑分散性提高,硫化胶的耐磨性能和耐压缩疲劳性能变化不大;当塑解剂DBD用量为0.05～0.11份时,硫化胶的物理性能较好.     

门尼粘度及支化程度对三元乙丙橡胶性能的影响

通过无转子硫化仪、橡胶加工分析仪、核磁交联密度仪等分析手段研究三元乙丙橡胶(EPDM)的门尼粘度、长链支化程度对过氧化物硫化EPDM的硫化特性及其硫化胶性能的影响。结果表明,门尼粘度的增加,有助于交联密度和硫化速率的提高,横向弛豫时间不断减小。高支化程度对EPDM胶料硫化速度不利。EPDM门尼粘度越高,初始储能模量G′0越大,储能模量迅速下降的临界应变值越小;不同长链支化度的EPDM硫化胶的储能模量大致相等,但长支化链的损耗因子值相对较高。门尼粘度对EPDM硫化胶拉伸强度变化影响较小;而长链支化程度的提高,使硫化胶拉伸强度和断裂伸长率略微降低。     

系列门尼粘度稀土异戊橡胶产品开发

采用Nd(vers)3-Al(i-Bu)2H-Al(i-Bu)2Cl均相稀土催化体系,以异戊二烯为单体和己烷为溶剂进行异戊二烯聚合反应,探讨稀土催化体系和聚合工艺条件对聚合物门尼粘度的影响规律,建立了不同条件下聚合物门尼粘度的关联曲线,提出稀土异戊橡胶门尼粘度优化控制方案。实验结果表明,稀土异戊橡胶门尼粘度随着催化剂中氢化二异丁基铝[Al(i-Bu)2H]与新癸酸钕[Nd(vers)3]配比、相对分子质量调节剂用量、催化剂用量和聚合温度的增加而降低;随着反应时间的增加而逐渐趋于稳定。开发出了门尼粘度为60±5、70±5、80±5、90±5的系列稀土异戊橡胶,满足不同橡胶制品对不同规格异戊橡胶产品的要求。     

GBW(E)130573门尼粘度标准物质不确定度的评定

研制GBW(E)130573门尼粘度标准物质,该标准物质的不确定度按照JJF 1059.1-2012规定分析不确定度各分量并进行评定。不确定度的来源主要为各定值实验室检测的分散性、样品的均匀性与稳定性、试验温度、试验时间、设备转速。经评定GBW(E)130573门尼粘度标准物质的不确定度为0.9。     

不同门尼黏度NBR的制备及其对力学性能的影响

本文利用两种不同门尼含量的胶乳,利用掺混法成功制备了不同门尼黏度的NBR,研究了不同门尼黏度NBR对硫化性能及其对力学性能的影响,结果表明:随着门尼黏度的增大,NBR的最大扭矩值越大;随着门尼黏度的增加,NBR胶料的断裂伸长率逐渐降低;门尼黏度越大,NBR胶料的拉伸应力越高,同时恢复曲线的应力也越高,马林斯效应越明显.     

丁二烯橡胶门尼粘度测试准确性的研究

门尼粘度分析结果与原料生产厂家提供的测试结果差距较大。对采样方法、分析步骤、分析过程及设备等引起误差的多方面进行了细化,减少了人为误差,提高了门尼粘度测试结果的准确性。     

Role of short polyisoprene chains in storage hardening of natural rubber

Drying of natural rubber (NR) crumb (grade TSR10) requires high temperatures (100–120 °C). In order to determine the changes in bulk viscosity during the drying process, ageing kinetics at 120 °C were studied on model NR samples. During the process, changes in Mooney viscosity and weight‐average molar mass (M_W) were monitored. Rubber from clones GT 1 and PR 107, with a bimodal inherent molar mass distribution (MMD₀), was degraded in a two‐phase process. During the first phase, Mooney viscosity and M_W increased, undoubtedly owing to a predominance of storage hardening over chain scissions [0 < t (min) <120]. During the second phase, chain scissions predominated (t > 120 min) and Mooney viscosity and M_W decreased. For rubber samples from clone PB 217, with a unimodal MMD₀, no or reduced storage hardening was observed throughout the ageing process. These results showed that the key parameter involved in storage hardening seems to be the quantity of short polyisoprene chains and probably the nature of the chain ends. Copyright © 2003 Society of Chemical Industry     

Better characterization of raw natural rubber by decreasing the rotor speed of Mooney viscometer: Role of macromolecular structure

The objective of our work was to characterize natural rubber (NR) samples with different macromolecular structures by measuring Mooney viscosities (V_R) at variable rotor speeds ≤2 rpm, called variable speed Mooney viscosity (M_VS). Model samples of technically specified rubbers of constant Mooney viscosity (TSR5CV) were prepared with chosen specific clones. The structures of the samples were characterized by size‐exclusion chromatography coupled with an online multi‐angle light‐scattering detector (SEC‐MALS). Rheological properties of the samples were also characterized by a dynamic moving die rheometer. Measuring monoclonal model samples by M_VS showed three types of V_R flow curves. The V_R at high rotor speed (2 rpm) was correlated with number‐average molar mass (M_n), whereas V_R at low rotor speed (0.05 rpm) was correlated with weight‐average molar mass (M_w). Measuring M_VS revealed the rheological behaviors of samples and enabled discrimination between samples with different macromolecular structures and should thus help in predicting processability. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

合成橡胶生胶门尼粘度比对结果对比分析

利用稳健统计技术对4次门尼粘度数据比对结果进行了分析,所有参加比对的实验室反映了该行业测试水平;国家橡胶及乳胶制品质量监督检验中心、国家石化有机原料合成树脂质量监督检验中心等质检机构和广州市华南橡胶轮胎有限公司检测中心、三角轮胎股份有限公司中心化验室等国家认可实验室的测试水平较高,科研开发实验室测试水平次之;独山子石化、兰州石化、申华化学工业有限公司等生产企业的实验室在4次数据比对中表现较好,数据满意,其他生产企业、加工企业的实验室能够满足测试要求;2011年数据比对测试水平高于往年数据比对测试水平;实验室测试水平均有不同程度的提高.     

高门尼粘度宽分布乙丙橡胶的合成

以三氯氧钒为主催化剂,以混合烷基铝为助催化剂,形成了三氯氧钒和混合烷基铝并用的催化体系,用该催化体系合成了具有相对分子质量分布宽的高门尼粘度乙丙橡胶。研究了混合烷基铝中三氯三乙基二铝（AQ）与三异丁基铝（AT）对聚合物相对分子质量分布的影响,并研究了氢气用量对聚合物相对分子质量和门尼粘度的调节作用、主催化剂的加入量对聚合物门尼粘度的影响以及m（A1）／m（V）配比对聚合催化效率的影响。     

Dependence of Mooney scorch time of SMR L,ENR 25, and ENR 50 on concentration and types of antioxidants

The effect of concentration of antioxidants on the Mooney scorch time of two grades of epoxidized natural rubbers (ENR 25 and ENR 50) and one grade of natural rubber (SMR L) was studied using a Monsanto automatic Mooney viscometer (MV 2000). Three types of antioxidants, viz., 2,2′‐methylene‐bis(4‐methyl, 6‐tertbutylphenol) (AO 2246), N‐isopropyl‐N′‐phenyl‐p‐phenylenediamine (IPPD) and poly‐2,2,4‐trimethyl‐1,2‐dihydroquinoline (TMQ) were used, and the concentration range was varied from 0 to 5 phr. The conventional vulcanization system with 2‐mercaptobenzothiazole (MBT) as the accelerator was used throughout the study. Results show that increasing the phenol‐based antioxidant (AO 2246) concentration will increase the scorch time of ENR at a lower temperature of vulcanization while its effect on SMR L is not significant. This retardation effect is attributed to the “solvation” of epoxide group by the phenolic group in AO 2246, thus reducing the activation of adjacent double bond in ENR. The scorch time, however, is shortened by the amine‐based antioxidants (IPPD and TMQ) for the three rubbers studied, a phenomenon associated with the ability of the amine group to enhance the formation of more active sulfurating agent and subsequently increases the cure rate as the concentration of the amine‐based antioxidants is increased. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2940–2946, 1999     

低门尼黏度CM专用树脂YEC-5515TL的工业化开发

在淤浆CX工艺装置上,采用专用主催化剂和改进的生产工艺条件,开发出低门尼黏度橡胶型氯化聚乙烯(CM)专用高密度聚乙烯(HDPE)YEC-5515TL。采用差示扫描量热仪、激光粒度分析仪、凝胶渗透色谱仪和扫描电子显微镜等研究了YEC-5515TL的结构与性能,和同类进口产品对比。结果表明:YEC-5515TL能满足低门尼黏度CM对原料HDPE的要求,用YEC-5515TL制备的CM综合性能均能达到低门尼黏度CM的要求。     

配方体系对HNBR/HXNBR并用胶门尼黏度和硫化特性的影响

采用门尼黏度仪和无转子硫化仪研究了氢化羧基丁腈橡胶(HXNBR)的添加量、硫化/活化体系和补强体系对氢化丁腈橡胶(HNBR)/HXNBR并用胶门尼黏度和硫化特性的影响.结果表明,随着HXNBR用量的增加,HNBR/HXNBR并用胶的门尼黏度呈线性增加趋势;过氧化二异丙苯(DCP)/三羟甲基丙烷三甲基丙烯酸酯(TRIM)...     

A Study of Rheological Behavior and Compatibility of NR/BR Blends

In this study, we research the Mooney viscosity, curing rates, and processibility of natural rubber (NR) and polybutadiene rubber (BR) blends at different blending ratios. The changing values are measured during vulcanization processing and were tested by Mooney viscometer, Monsanto viscometer, etc. The results of scanning electron microscope (SEM) and dynamic mechanical analysis (DMA) experiments are used to explore the surface morphologies and molecular mobility of NR/BR blends.

The experimental results indicate that Mooney viscosity tends to decrease with increasing NR content of NR/BR blends, and this results in superior processibility of NR/BR blends with increasing NR content. NR/BR blends' curing rate improved with increasing NR content. The DMA experimental results show that the temperature is suitable to produce a character peak (T_αn) in molecular motions of NR/BR blends. There tends to a lower temperature range with decreasing NR content of NR/BR blends. In addition, T_αb would move to a lower temperature with decreasing BR content of NR/BR blends.