From the Volume‐Filling Effect to the Stress‐Bearing Network: The Reinforcement Mechanisms of Carbon Black Filler in Natural Rubber

Using synchrotron‐radiation X‐rays for nanoscale computed tomography (X‐ray nano‐CT), the structure and corresponding reinforcement effects of carbon black (CB) filler at various amounts in natural rubber (NR) are studied during cyclic loading. All structural parameters of the CB filler, which are extracted from X‐ray images—such as the destruction and reconstruction ratios of the aggregates and the network connectivity, show a transition point with the CB content at around 30 phr (phr = parts by weight per hundred parts of rubber). When the CB content is above the transition point, the effective volume fraction exceeds the percolation threshold, and a stress‐bearing filler network can form; this network can effectively transmit the external stress to the entire sample and abruptly enhance the reinforcement factor. Below the percolation threshold, the CB filler is mainly disconnected aggregates, where its reinforcement of the rubber matrix can be mainly described by the volume‐filling effect. Using the dynamic cluster–cluster aggregation (CCA) model, calculations of the mechanical properties related to the CB content suggest that the network structure plays a major role in the reinforcement of the NR.

     

The Effect of Carbon Black/Multiwall Carbon Nanotube Hybrid Fillers on the Properties of Natural Rubber Nanocomposites

The properties of hybrid multiwall carbon nanotube (MWCNT) and carbon black (CB) in natural rubber nanocomposites were studied. The results show that the scorch and cure time decreased as the MWCNT loading increased in CB/MWCNT hybrid loading ratio but for the maximum torque, the result shown otherwise. As the MWCNT loading increased in CB/MWCNT hybrid loading ratio, the tensile strength, elongation at break and fatigue life are decrease, however the tensile modulus and rubber filler-interaction (Q_f/Q_g) value increased. The SEM results show a dispersion of CB and MWCNT in natural rubber matrix. Furthermore, the thermal stability for the hybrid nanocomposites is enhanced.     

炭黑填充硫化胶的网络结构同力学性能间相关性——(Ⅱ)炭黑的补强作用和它的表征

本文从炭黑填充和未填充硫化胶的弹性形变自由能和应力一应变关系式出发,利用两者形变自由能和形变应力的差值法,提出了三种炭黑补强作用的表征方法:多余形变自由能、多余形变应力和模量法,后者能定量地区分物理补强,化学补强和短链补强作用.最后以不同炭黑品种和用量填充硫化的天然胶,合成异戊胶和丁苯胶等的大量应力一应变实验数据验证了炭黑填充硫化胶大形变弹性分子理论、补强作用理论和三种补强作用的表征方法,结果表明在给定品种和用量范围内理论同实验均能较好地符合.并讨论了抗张强度同炭黑品种的依赖性.     

过硫酸铵改性炭黑／天然胶乳复合材料的制备与性能研究

摘要：用过硫酸铵水溶液改性炭黑,制备亲水性炭黑悬浮液。采用乳液共混法,将制备的改性炭黑水溶液直接加入天然胶乳。结果表明：改性后炭黑表面亲水性含氧基团增多,粒径减小;与传统干法混炼炭黑,天然橡胶胶料相比,乳液共混改性炭黑／天然胶乳复合材料炭黑分散粒径小且分散均匀,复合材料拉伸强度和撕裂强度显著提高。     

Dynamic Mechanical Properties of Carbon Black Filled Ethylene Vinyl Acetate Rubber

Abstract

The dynamic mechanical properties of ethylene vinyl acetate (EVA) rubber filled with different loadings of carbon black and at different degrees of crosslinking were studied over a wide range of temperatures (-150° to +200°C). The loss tangent (tan δ) versus temperature plots indicated presence of different transitions. The α-transition (or the glass-rubber transition) corresponding to the maximum in tan δ value, occurred at ?17°C, which is the principal glass-transition temperature (abbreviated as T _g) of EVA rubber. The γ-transition occurred in the temperature region of ?125° to ?135°C, while the β-transition appeared as a shoulder in the temperature region of ?65° to ?75°C. Besides, there was also a high tempeature transition around +62°C which is known as liquid to liquid transition (T _1.1). Incorporation of carbon black filler did not cause any shift of T _g, while the tan δ peak values at T _g decreased sequentially with increase in filler loading. The γ- and β-relaxations were found to be insensitive to filler loading. The T _1.1 transition, however, was found to be suppressed by incorporation of carbon black filler particularly at high loading. Extent of crosslinking did not influence the T _g But, the T _1.1 transition, which was prominent with the lightly crosslinked system was found to be suppressed at high level of crosslinking. Strain dependent dynamic mechanical properties under isothermal conditions showed that the secondary structure breakdown of carbon black filler under the effect of strain amplitude is influenced by the degree of crosslinking of EVA rubber.     

炭黑填充硫化胶的网络结构同力学性能间相关性——(Ⅰ)炭黑填充硫化胶大形变弹性分子理论

本文提出了炭黑填充硫化胶的网络结构是由交联网,缠结网和炭黑——高分子链网所形成的网络结构模型.基于该微观结构模型和弹性大形变机理用统计力学方法计算了三种网中各链组的末端距机率密度分布函数,三种网的形变自由能和炭黑填充硫化胶的总形变自由能,并根据弹性形变自由能同应力一应变间的关系得到了四种简单形变方式的应力一应变关系式.     

硅烷偶联剂KH550对炭黑填充天然橡胶性能的影响

研究不同用量的硅烷偶联剂KH550对炭黑填充天然橡胶的硫化特性、物理性能和动态力学性能的影响。结果表明,硅烷偶联剂KH550的加入缩短了焦烧时间和正硫化时间;硅烷偶联剂KH550添加量为2份时邵尔A型硬度和拉伸强度达到最大值,拉断伸长率有所降低,回弹性和压缩永久变形性能有明显改善;硅烷偶联剂KH550的加入能有效降低炭黑的Payne效应,提高胶料的交联密度及炭黑的分散性,硫化胶损耗因子和动态生热降低,动态力学性能明显改善。     

辐射预硫化炭黑/白炭黑天然橡胶胶料性能对比研究

对炭黑和白炭黑分别填充的天然橡胶(NR)胶料进行电子辐射预硫化,研究辐射预硫化对胶料的结合胶含量、门尼粘度和硫化特性及硫化胶的物理性能和动态性能的影响。结果表明,辐射预硫化能提高胶料的结合胶含量、门尼粘度和硫化速度,对两种硫化胶的应力应变、生热和磨耗等性能产生不同的影响,并能显著抑制填料在橡胶基体内网络结构的形成,降低胶料的滞后损失。     

The Properties of Acrylonitrile-Butadiene Rubber (NBR) Composite with Halloysite Nanotubes (HNTs) and Silica or Carbon Black

The properties of acrylonitrile-butadiene rubber (NBR) composites were studied at five different compositions of NBR/HNTs/Silica or NBR/HNTs/CB (i.e., 100/5/0, 100/4/1, 100/3/2, 100/2/3, 100/0/5 parts per hundred rubber (phr)). The tensile strength and modulus (M100) of both composites decreased, whereas elongation at break increased and maximum torque with increasing the silica or carbon black content. However, both composites show opposite trends for cure time and scorch time, where NBR/HNTs/Silica composite exhibited an increasing trend, while NBR/HNTs/CB composite shows the decreasing trend. The rubber-filler interaction studies showed that carbon black is a more reinforcing filler than silica.     

Preparation and Characterization of Natural Rubber Composites Comprising Conductive Carbon Black/Magnetite Hybrid Fillers Obtained by Impregnation Technology

Hybrid fillers have been prepared of conductive carbon black/magnetite at various ratios of the phases: 90:10, 70:30, and 50:50. The fillers have been characterized and their effect on the curing, mechanical, electric, and dynamic properties of natural rubber–based vulcanizates has been also investigated. The macrohomogeneity of the composites has been evaluated by ohmic resistivity measurements and correlation analysis. It has been established that all properties studied are dependent on the ratio between the filler’s phases. Viewing their composition, we conclude that the hybrid fillers are expected to exhibit both high dielectric and magnetic losses and may find application in the manufacturing of microwave absorbers.     

Comparison Properties of Natural Rubber (SMR L)/Ethylene Vinyl Acetate (EVA) Copolymer Blends and Epoxidized Natural Rubber (ENR-50)/Ethylene Vinyl Acetate (EVA) Copolymer Blends

Mixing torque, morphology, tensile properties and swelling studies of natural rubber/ethylene vinyl acetate copolymer blends were studied. Two series of unvulcanized blends, natural rubber/ethylene vinyl acetate (SMRL/EVA) copolymer blend and epoxidized natural rubber (50% epoxidation)/ethylene vinyl acetate (ENR-50/EVA) copolymer blend were prepared. Blends were prepared using a laboratory internal mixer, Haake Rheomix polydrive with rotor speed of 50 rpm at 120°C. Results indicated that mixing torque value and stabilization torque value in ENR-50 blends are lower than SMRL blends. The process efficiency of ENR-50/EVA blends is better due to less viscous nature of the blend compared to SMRL/EVA blends as indicated in stabilization torque graph. Tensile properties like tensile strength, M100 (modulus at 100% elongation) and E _b (elongation at break) increase with increasing EVA fraction in the blend. At the similar blend composition, ENR-50 blend shows better tensile properties than SMRL blends. In oil resistance test, swelling percentage increased with immersion time and rubber composition. At a similar immersion time, ENR-50 blends exhibit better oil resistance compared to SMRL blends. Scanning electron microscopy (SEM) of tensile fractured surface indicated that EVA/ENR-50 blends need higher energy to cause catastrophic failure compared to EVA/SMRL blends. In etched cryogenically fractured surface, size and distribution of holes due to extraction of rubber phase by methyl ethyl ketone (MEK) were studied and holes became bigger as rubber composition increased due to coalescence of rubber particle.     

炭黑聚集体在橡胶中的力学性能分析

利用Digimat多尺度分析软件建立了五种不同体积分数和相同体积分数下五种不同炭黑聚集形态的多颗粒炭黑聚集体随机分布的三维代表体积单元模型,研究了橡胶形变、应力集中和炭黑聚集体形态对橡胶力学性能的影响。结果表明：通过与文献模拟结果和实验数据比较验证了本文模型是合理的;炭黑聚集体的形变很小,应力集中点主要位于炭黑聚集体与炭黑聚集体相接近的区域;发现用三棱柱和二十面体模型描述炭黑聚集体形态更能真实地反映橡胶的力学行为。     

纳米导电纤维与导电炭黑并用填充硅橡胶胶料的流变性能

考察了纳米导电纤维（ＮａｎｏＦ）／导电炭黑填充硅橡胶胶料的流变性能。结果表明,在低剪切速率下,ＮａｎｏＦ的各向异性增加了硅橡胶分子链缠结点,阻碍其在流场中的取向,提高了胶料的表观粘度;在高剪切速率下,ＮａｎｏＦ的取向有助于硅橡胶分子链的取向运动,可降低胶料的表观粘度,改善胶料的加工性能。     

Preparation of Pyrolytic Carbon Black from Scrap Tire Rubber Crumb and Evaluation in New Rubber Compounds

Summary: Pyrolytic carbon black (CBp) has been prepared by rubber crumb pyrolysis under nitrogen flow at 700 °C. The CBp obtained by this process had an average surface area of 81 m² · g^?1 and was obtained in 43% yield over the starting rubber crumb. Although the CBp surface area can be increased up to 109 m² · g^?1 by washing away the Zn‐ and Si‐based ashes with HF treatment, the CBp was tested in a standard NR/SBR‐based formulation without any purification and ash extraction. CBp was tested at increasing loading levels as partial or full replacement of a standard N339 furnace carbon black. CBp depresses the physical properties of the rubber compound in a way which is directly proportional to the amount added. The reason of this result and the limited reinforcing effect is discussed in terms of low surface area and low structure in comparison to N339 carbon black as well as in terms of low surface activity, the interference of the ashes and the poor dispersion. Ideas of further development works are outlined.

     

RPA8000橡胶加工分析仪在炭黑补强性能检测中的应用

采用RPA8000橡胶加工分析仪对炭黑添加到橡胶后补强性能进行测试,结果发现,所测的弹性模量、补强因子与胶料的拉伸强度有很好的相关性,可直观的反映炭黑添加到橡胶后的补强性能,检验过程简单,减小了检测过程的影响因素,适当提高了炭黑在橡胶的补强性能测试效率。     

Effects of γ-Radiation Treatment on the Reinforcing Properties of Carbon Black in Rubber Compound

Abstract

Commercial graphite flakes and carbon black grade N234 have been subjected to γ-radiation treatment to a total dose of IMGy. The resulting radiation-damaged materials were studied by Raman spectroscopy. Raman spectra have revealed that graphite underwent substantial changes in its structure with formation of hexagonal diamond sites as well as onion-like and amorphous carbon domains. Changes also in the Raman spectra of irradiated carbon black have been observed which could be interpreted in the light of the results on irradiated graphite.

A compound evaluation of γ-treated carbon black has been performed in comparison to a pristine sample. The results show a spectacular increase in the reinforcing effect as measured by the 200% and 300% modulus, hence an increase of the filler-to-polymer interaction, a reduction of the Payne effect and of the hysteresis (measured by tand at 70[ddot]C).     

分子结构及炭黑粒子对丁苯橡胶挤出流变特性的影响

本工作主要通过毛细管流变仪,并结合多种表征测试手段,考察了丁苯橡胶分子结构以及炭黑用量对胶料挤出流变特性的影响。结果表明：ESBR1712纯胶及填充胶表观剪切黏度均大于SSBR2564A;ESBR1712与SSBR2564A两种纯胶的挤出稳定性相近,但炭黑填充SSBR2564A混炼胶的挤出稳定性更为优异,挤出物外观质量较好;与SSBR2564A相比,ESBR1712分子链柔顺性更好,炭黑在该体系中的分散性更好,结合胶含量更高。     

Effect of In Situ Polymerization of Styrene onto Natural Rubber on Adhesion Properties of Styrene-Natural Rubber (SNR) Adhesives

Styrene-based deproteinized natural rubber (SNR) latex was synthesized by in situ polymerization. Three pre-vulcanization systems [conventional-cured (CV), semi-efficient-cured (Semi-EV), and efficient-cured (EV)] were studied in terms of tensile and adhesion properties. Good tensile properties were observed for CV and EV SNR. The Semi-EV SNR showed the best adhesion properties based on the good anchorage performance in all substrate pairings (polystyrene–polystyrene, polystyrene–rubber, and rubber–rubber). The pH modification on SNR latex via KOH addition has beneficial effects of removing protein layers, resulting in more styrene grafting sites in the rubber molecules. Consequently, the tensile and adhesion properties of the SNR are improved as more styrene polymers are grafted onto the rubber matrix. Semi-EV SNR with pH 12 has superior adhesive performance; hence, it is suitable for use as a pressure-sensitive adhesive.