Anisotropy in injection-molded ethylene-propylene-diene rubbers. Part II: Disks delaminated by a water-jet cutting technique

Anisotropy and molecular orientation are well known phenomena in the field of thermoplastics, but only a few studies have described anisotropy in rubber materials. It has been shown that injection molding gives rise to a higher degree of anisotropy than compression molding. The anisotropy in the rubber material was strengthened by carbon black and is presumably due to molecular orientation. This paper describes the anisotropy of injection-molded ethylene-propylene-diene rubbers. The two polymers had different molecular weight distributions and thus different rheological properties. The compounds were injected into center-gated 4mm thick disks. The disks were subsequently split into three layers using a water-jet cutting technique. Measurement of mechanical and swelling properties in the different layers and directions showed that the anisotropy varied through the thickness of the disk. By X-ray scattering it was shown that rubber molecules had a preferred direction and thus, that the anisotropy was probably predominantly due to molecular orientation created during the mold filling.     

Effect of carbon black on the mechanical and dielectric properties of rubber ferrite composites containing barium ferrite

Fine particles of barium ferrite (BaFe₁₂O₁₉) were synthesized by the conventional ceramic technique. These materials were then characterized by the X‐ray diffraction method and incorporated in the natural rubber matrix according to a specific receipe for various loadings of ferrite. The rubber ferrite composites (RFC) thus obtained have several applications, and have the advantage of molding into complex shapes. For applications such as microwave absorbers, these composites should have an appropriate dielectric strength with the required mechanical and magnetic properties. The N330 (HAF) carbon black has been added to these RFCs for various loadings to modify the dielectric and mechanical properties. In this article we report the effect of carbon black on the mechanical and dielectric properties of these RFCs. Both the mechanical and dielectric properties can be enhanced by the addition of an appropriate amount of carbon black. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 769–778, 2003     

Overall properties of fibrillar silicate/styrene–butadiene rubber nanocomposites

The mechanical properties, heat aging resistance, dynamic properties, and abrasion resistance of fibrillar silicate (FS)/styrene butadiene rubber (SBR) nanocomposites are discussed in detail. Compared with white carbon black (WCB)/SBR composites, FS/SBR composites exhibit higher tensile stress at definite strain, higher tear strength, and lower elongation at break but poor abrasion resistance and tensile strength. Surprisingly, FS/SBR compounds have better flow properties. This is because by rubber melt blending modified FS can be separated into numerous nanosized fibrils under mechanical shear. Moreover, the composites show visible anisotropy due to the orientation of nanofibrils. There is potential for FS to be used to some extent as a reinforcing agent for rubber instead of short microfibers or white carbon black. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2725–2731, 2006     

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。     

活性硅格粉与炭黑结合机理与生产工艺探索

炭黑、硅格粉两者都是橡胶的无机填充料,炭黑主补强功能,增强橡胶轮胎的耐磨性能,提高使用寿命,硅格粉主伸展功能,提高橡胶的伸长率,减少形变生热,降低橡胶轮胎的滚动阻力。但由于硅格粉分子内含有较多的活性官能团,直接在橡胶中投加使用时分子内基团相互作用较多,导致硅格粉在橡胶中分散不均匀,形成大颗粒状及块状分布,反而破坏了橡胶的性能。因此本研究开发将这两种无机材料进行化学结合,将硅格粉的优势性能赋予到炭黑上,形成一种新型的双相炭黑,突破轮胎的“魔鬼三角”,提高胶料的物理机械性能、减少胶料滞后、降低轮胎的滚动阻力而又不损失抗湿滑性能。     

Application of rice husk ash as fillers in the natural rubber industry

Rice husk ash (RHA) obtained from agricultural waste, by using rice husk as a power source, is mainly composed of silica and carbon black. A two‐stage conventional mixing procedure was used to incorporate rice husk ash into natural rubber. For comparison purposes, two commercial reinforcing fillers, silica and carbon black, were also used. The effect of these fillers on cure characteristics and mechanical properties of natural rubber materials at various loadings, ranging from 0 to 40 phr, was investigated. The results indicated that RHA filler resulted in lower Mooney viscosity and shorter cure time of the natural rubber materials. The incorporation of RHA into natural rubber improved hardness but decreased tensile strength and tear strength. Other properties, such as Young's modulus and abrasion loss, show no significant change. However, RHA is characterized by a better resilience property than that of silica and carbon black. Scanning electron micrographs revealed that the dispersion of RHA filler in the rubber matrix is discontinuous, which in turn generates a weak structure compared with that of carbon black and silica. Overall results indicate that RHA can be used as a cheaper filler for natural rubber materials where improved mechanical properties are not critical. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 34–41, 2005     

铁水脱硫渣做填料对橡胶材料力学性能的影响

以铁水脱硫渣做天然橡胶填料制备橡胶材料,研究铁水脱硫渣/炭黑配比、铁水脱硫渣粒径和硫化时间对橡胶材料力学性能的影响.结果表明,铁水脱硫渣/炭黑配比为20∶30时,橡胶材料的力学性能降低幅度较小,实现最大化利用铁水脱硫渣.橡胶材料中铁水脱硫渣粒径过大或过小均会造成其在天然橡胶中的分散性与相容性变差,导致力学性能降低;当硫化时间为30 min,橡胶材料力学性能最优.     

用作载重子午线轮胎胎面胶的炭黑填充粉末NR结构与性能研究

以天然胶乳和炭黑N234为原料,采用凝聚共沉法制备炭黑填充型粉末NR[P(NR/CB)],研究炭黑用量和不同配方对胶料硫化特性、物理性能、交联密度、微观结构、Payne效应及动态力学性能的影响,并与采用传统机械混炼法制备的炭黑/NR(CB/NR)进行对比.结果表明,与CB/NR硫化胶相比,P(NR/CB)硫化胶具有较高的拉伸强度、撕裂强度、回弹值和抗湿滑性能以及较低的滚动阻力,耐屈挠性能和耐磨性能大致相当,而动态压缩生热和压缩永久变形则降低了近50%.     

3-Aminopropyltriethoxysilane as a promoter in the crosslinking of carboxylated nitrile rubber by surface-oxidized carbon black

The role of aminopropyltriethoxysilane in the interaction between ISAF carbon black and carboxylated nitrile rubber was studied by measurements of bound rubber, physical and dynamic mechanical properties of the vulcanizates, and Monsanto Rheometric studies on the rubber-filler mixes. It is believed that  NH₂ groups of the silane interact with  COOH groups of the rubber, while  OC₂H₅ groups of the silane interact with  OH groups on the filler surface. Weak rubber-filler bonds formed during mixing are converted into a crosslinked structure during high-temperature molding. The extent of crosslinking of the rubber phase by the active sites on the filler surface is greater in the case of oxidized ISAF carbon black, as compared to the nonoxidized grade. © 1996 John Wiley & Sons, Inc.     

Influence of carbon black in polychloroprene organoclay nanocomposite with improved mechanical,electrical and morphology characteristics

Abstract

The effect of carbon black on nanoclay filled polychloroprene (CR) composites has been investigated. The nanoclay loading is fixed at 5 part per hundred rubbers (phr), and carbon black loading varied from 5 to 20 phr in rubber compounds. The rubber nanocomposites are prepared in laboratory by mixing in two-roll mill. The addition of nanoclay enhances mechanical properties especially tear strength and decreases water absorption without change in electrical properties compared to gum rubber vulcanisates. Wide angle X-ray diffraction and transmission electron microscopy are used to study the microstructure of CR nanocomposites. The addition of 5 parts of nanoclay to 15 phr carbon black filled samples shows synergistic effect between the fillers and suggests that the reinforcement is due to a more developed filler network formation in hybrid filler system than that in single phase filler. Significant improvement in mechanical, electrical and low water absorption properties has been obtained with these nanoclay and carbon black filled rubber nanocomposites. The paper concludes that nanocomposites containing a mixture of organoclay and carbon black in right proportion can be a substitute for rubber components used in underwater cable and device encapsulation applications.     

机械混炼制备碳纳米管/天然橡胶复合材料特性分析

通过机械混炼方法将碳纳米管与天然橡胶复合，与炭黑补强样品相比，碳纳米管在橡胶中的混入速度快，功率消耗低，温升幅度小，混炼胶的硫化焦烧时间略有增加，硫化返原现象减轻，硫化剂用量应适当增加。加入碳纳米管后，橡胶DSC曲线中的结晶熔融峰面积减少，交联反应放热峰变宽。碳纳米管复合材料的回弹、压缩疲劳性能明显优于炭黑补强样品，耐老化性能较好，拉伸、撕裂性能水平有待提高。     

工程车辆翻新轮胎补强剂性能补强试验及机理

为了改善工程车辆翻新轮胎在使用中经常出现胎面不耐磨、易崩花掉块的损坏形式,将炭黑、白炭黑作为补强剂加入到胎面基体配方中,通过改变用量及加料顺序,对三种不同配方体系下的胎面进行拉伸强度、撕裂强度、300%定伸应力、拉断伸长率、耐磨指数、硬度及炭黑分散度扫描等物理机械性能进行测试,获得了如下主要结论：单一炭黑配方体系中,当炭黑N151质量份为40,混合配方体系中,当炭黑N330质量份为40、白炭黑质量份为20时,性能补强效果较为理想,耐磨性及抗崩花掉块性能大大提高。应用分子链滑动理论解释了炭黑的补强机理,炭黑颗粒与橡胶分子链之间需要保持一个合适的吸附比表面积,需要炭黑含量达到一个最佳值,炭黑含量过低,橡胶分子链不能紧密融合,炭黑含量过高,会导致炭黑颗粒间空隙小,同样橡胶分子链不能有效融合,补强效果不理想。     

Elastomer–carbon black interaction: Influence of elastomer chemical structure and carbon black surface chemistry on bound rubber formation

The contribution of elastomer polarity and reactivity to bound rubber formation has been investigated. In this study, a number of elastomers of different chemical nature have been tested. The surface of the carbon black (N110) has also been modified by nitric acid oxidation in order to increase the concentration of surface functional groups. The experimental results have shown that the bound rubber formation is barely related to the polarity of the polymers. It is the reactive sites in both the elastomer and carbon black which are mainly responsible for bound rubber formation. It therefore appears that the elastomer/carbon black interaction leading to the formation of bound rubber is essentially a chemical process involving primary bond formation between elastomer and carbon black. The oxidized carbon black exhibits a higher surface activity which may be due to an increased concentration of oxygen-containing reactive surface sites, namely, phenolic hydroxyl, carboxyl, lactone, and quinone groups. © 1995 John Wiley & Sons, Inc.     

1,3,5‐trihydroxy benzene as a surface modifier of carbon black and its effect on the filler–rubber interaction

A surface‐modified rubber‐grade carbon black has been prepared by treating it with 1,3,5‐trihydroxy benzene (phluroglucinol) in aqueous solution at different molar concentrations. This modified carbon black has been used as one of the compounding ingredients with natural rubber. An attempt has been made to establish a concentration optimum for the modifier. Improved physicomechanical properties like hardness, heat buildup, hysteresis loss, and improved dynamic mechanical properties are observed for the compounded rubber. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2272–2278, 2003     

Reinforcing mechanisms of carbon nanotubes and high structure carbon black in natural rubber/styrene‐butadiene rubber blend prepared by mechanical mixing − effect of bound rubber

The reinforcing effect of high structure carbon black (HSCB) and multi‐walled carbon nanotubes (MWCNTs) on natural rubber/styrene‐butadiene rubber blend processed using mechanical mixing was comparatively investigated. In‐depth analysis by dynamic mechanical analysis, the Eggers ? Schummer model and Medalia's relationship showed that HSCB aggregates provided large internal pores leading to significant immobilized macromolecules in filled rubber. Additionally, a tubular immobilized rubber layer with a thickness of 8 nm was estimated for the rubber/MWCNT system based on dynamic mechanical analysis data. The mechanical performance of the HSCB filled blend was higher than that of the MWCNT filled blend at the same loading which was correlated to its higher bound rubber content. Both bound rubber content and filler anisotropy were found to govern the overall mechanical properties of rubber/MWCNT composites. Stress softening was correlated with rupture energy suggesting hysteretic failure mechanisms in both MWCNT and HSCB filled rubbers. © 2015 Society of Chemical Industry     

新型橡胶补强填料的研究开发现状

概述了橡胶补强填料的发展状况，并对国内外新近出现的橡腔补强填料作了详细的介绍。目前，国内外橡胶补强填料的研究主要集中在硅酸盐矿物、固体废弃物以及纳束材料等领域。新型橡胶补强填料的出现减少了橡胶工业对炭黑、白炭黑的过度依赖，并降低石油消耗和橡胶加工成本，为橡胶工业的发展做出了很大的贡献。     

Improving the crack resistance of bulk molding compounds and sheet molding compounds

Fiber-reinforced plastics exhibit two types of mechanical failure: gross fracture and microcracking. Gross fracture involves both matrix and fiber failures. Principal resistance to crack propagation derives from partial decoupling of fibers and then stressing, remove finite volumes of them to fracture. Classical concepts of fracture mechanics can be applied to such composites, though modifications of methodology to treat anisotropy and other special effects are required. Microcracking occurs principally in the matrix phase and usually accompanies cyclic fatigue, drop impact, bending, or rapid cooling from molding temperatures. It lowers composite stiffness, environmental resistance and may reduce strength. Matrix resins require high fracture toughness to minimize or eliminate microcracking. This paper discusses cracking in bulk molding compounds and sheet molding compounds, complex materials containing high percentages of glass fibers and calcium carbonate filler. Microcracking can be greatly reduced by tire addition of small amounts of a rubber to the polyester matrix. Various tests such as impact, bending, acoustic emission and crack propagation demonstrate the improved toughness properties which result. No sacrifice of original strength characteristics occurs, and markedly improved resistance to damage has been noted with rubber modified epoxy and polyester matrix resins.     

The impact of a fullerene-like concept in carbon black science

A discussion on the role of fullerene-like structure in carbon black has been presented. Starting from the definition of fullerene-like structure, from the experimental detection of these sites and from general properties of fullerenes, it is shown the electron affinity of fullerene-like structures in carbon black should exceed that of C₆₀ fullerene. Therefore the fullerene-like sites in carbon black should act as free radical acceptor sites where the rubber chain macroradicals formed by chain scission or hydrogen abstraction during mixing could add in competition with other known sites, to form chemical bonds, grafting the rubber on the carbon black surface. Fullerene-like structures in carbon black play a crucial role in bound rubber formation. Techniques to increase their concentration in order to improve the carbon black reinforcing effect and to reduce the mechanical hysteresis of the rubber compound containing the modified carbon black are briefly discussed.     

Bound rubber in elastomers: Analysis of elastomer-filler interaction and its effect on viscosity and modulus of composite systems

Bound rubber measurement may be very misleading as a measure of elastomer–carbon black interaction because sometimes only part of the apparently bound rubber is truly adsorbed on the carbon black surface. A theory is proposed which utilizes bound rubber measurements, but separates truly adsorbed rubber from other insoluble gel and enables calculation of the adsorbed elastomer layer thickness, a numerical value of interaction. Measurements of interaction were obtained for many different rubbers, including polybutadienes, styrene–butadienes, EPDMs, and butyl, with several different furnace blacks. An equation for viscosity of a rubber–carbon black composite is proposed, based on the degree of interaction obtained from the theory and the possible varying degree of orientation of the composite as the rate of shear is changed. This has been applied experimentally both to soluble elastomers and to an elastomer containing a nonrigid gel. The modulus of a vulcanized composite is shown to be related to the effective volume fraction of filler, which is equivalent to the volume fraction of filler plus adsorbed rubber, at temperatures above the glass transition temperature, regardless of the type of rigid filler. Below the glass transition temperature, the modulus depends only on the filler volume concentration.     

Recyclability of a continuous e-glass fiber reinforced polycarbonate composite

Fiber reinforced plastics are multi-component materials for which physical properties are strongly dependent on fiber and resin structure. Despite the disruptive nature of recycling methods on such structures, these materials nevertheless can be recycled. In this report, the recyclability of a fiber-reinforced cyclic BPA polycarbonate has been studied. It is found that ground up composite is recyclable and possesses properties as good as or better than a comparable commercial composite. The processing techniques investigated herein are injection, extrusion compression, and compression molding. As expected, processing technique and parameters are important in determining the mechanical properties of the molded regrind. Our results show that injection and extrusion compression molding yield recycled composites with good tensile properties, though the impact strengths are relatively low. This is due to high fiber orientation and fiber bundle dispersion. On the other hand, compression molded samples, which show random fiber orientation and low fiber bundles dispersion have relatively low tensile properties, but excellent impact strength. Results are discussed in terms of microstructural details, which include resin molecular weight and fiber length and orientation.