Plasma polymerization of acetylene onto silica: an approach to control the distribution of silica in single elastomers and immiscible blends

Surface modification of silica by acetylene plasma polymerization is applied in order to improve the dispersion in and compatibility with single rubbers and their blends. Silica, used as a reinforcing filler for elastomers, is coated with a polyacetylene (PA) film under vacuum conditions. Water penetration measurements show a change in surface energy due to the PA‐film deposition. The weight loss measured by thermo‐gravimetric analysis (TGA) is higher for the PA‐coated silica compared to the untreated filler, confirming the deposition of the PA film on the silica surface. Time of flight‐secondary ion mass spectrometry (ToF‐SIMS) shows the well‐defined PA cluster peaks in the high mass region. Scanning electron microscopy (SEM) measurements show silica aggregates, coalesced by the coating with smooth and uniform surfaces, but without significant change in specific surface area. Elemental analysis by energy dispersive X‐ray spectroscopy (EDX) measurements also confirms the deposition of the polymeric film on the silica surface, as the carbon content is increased. The performance of single polymers and their incompatible blends based on S‐SBR and EPDM, filled with untreated, PA‐ and silane‐treated silica, is investigated by measurements of the bound rubber content, weight loss related to bound rubber, cure kinetics, reinforcement parameter, Payne effect, and mechanical properties. The PA‐ and silane‐modified silica‐filled pure S‐SBR and EPDM samples show a lower filler–filler networking compared to the unmodified silica‐filled elastomers. Decrease in the reinforcement parameter (α_F) for the plasma‐polymerized silica‐filled samples also proves a better dispersion compared to silane‐modified and untreated silica‐filled samples. On the other hand, the PA‐silica‐filled samples show a higher bound rubber content due to stronger filler–polymer interactions. Finally, the PA‐silica‐filled pure EPDM and S‐SBR/EPDM blends show high tensile strength and elongation at break values, considered to be the result of best dispersion and compatibilization with EPDM. Copyright © 2008 John Wiley & Sons, Ltd.     

The effect of alkanolamide loading on properties of carbon black-filled natural rubber (SMR-L), epoxidised natural rubber (ENR), and styrene-butadiene rubber (SBR) compounds

The effect of Alkanolamide (ALK) loading on properties on three different types of carbon black (CB)-filled rubbers (SMR-L, ENR-25, and SBR) was investigated. The ALK loadings were 1.0, 3.0, 5.0 and 7.0 phr. It was found that ALK gave cure enhancement, better filler dispersion and greater rubber–filler interaction. ALK also enhanced modulus, hardness, resilience and tensile strength, especially up to 5.0 phr of loading in SMR-L and SBR compounds, and at 1.0 phr in ENR-25 compound. Scanning electron microscopy (SEM) proved that each optimum ALK loading exhibited the greatest matrix tearing line and surface roughness due to better rubber - filler interaction.     

Aging properties of styrene-butadiene rubber nanocomposites filled with carbon black and rectorite

To better understand the effect of rectorite and carbon black (CB) on the aging performance of styrene-butadiene rubber (SBR), SBR/CB, SBR/CB/rectorite and SBR/rectorite nanocomposites with the same total filler loading were prepared. The microstructure of the three SBR nanocomposites was characterized by XRD, TEM and SEM. After thermal aging, oxygen-containing molecules were found to be formed in the SBR nanocomposites, as verified by FTIR analysis. The SBR/rectorite nanocomposite showed the highest aging coefficient and the lowest change rate of tensile strength and stress at 100% strain among the three SBR nanocomposites, indicating that the introduction of nano-dispersed rectorite layers can enhance the thermal aging resistance of the nanocomposites. For the SBR/CB/rectorite nanocomposite, the addition of CB helped to improve the interfacial compatibility between the filler and matrix, resulting in the best crack resistance as the aged SBR/CB/rectorite nanocomposite always demonstrated the least cracks on the surface during either stretching or bending experiments.     

Filler‐polymer interactions of styrene and butadiene units in silica‐filled styrene–butadiene rubber compounds

Styrene–butadiene rubber (SBR) is a copolymer of styrene and butadiene, and the butadiene unit is composed of cis‐1,4‐, trans‐1,4‐, and 1,2‐components. Filler‐polymer interactions of each component of SBR in silica‐filled SBR compounds were examined by microstructure analysis of the bound and unbound rubbers. The composition ratio of butadiene and styrene units (butadiene/styrene) of the bound rubber was higher than that of the compounded rubber. Of the butadiene units, the 1,2‐component of the bound rubber was more abundant than the cis‐1,4‐ and trans‐1,4‐components. The filler‐polymer interaction of the butadiene unit with silica was stronger than that of the styrene unit, and the interaction of the 1,2‐component was stronger as compared with the others. The butadiene–styrene ratio of the bound rubber of the compounds containing the silane coupling agent was lower than for the compounds without the silane. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 577–584, 2004     

Nonlinear rheological behavior of silica filled solution‐polymerized styrene butadiene rubber

The reinforcement and nonlinear viscoelastic behavior have been investigated for silica (SiO₂) filled solution‐polymerized styrene butadiene rubber (SSBR). Experimental results reveal that the nonlinear viscoelastic behavior of the filled rubber is similar to that of unfilled SSBR, which is inconsistent with the general concept that this characteristic comes from the breakdown and reformation of the filler network. It is interesting that the curves of either dynamic storage modulus (G′) or loss tangent (tan δ) versus strain amplitude (γ) for the filled rubber can be superposed, respectively, on those for the unfilled one, suggesting that the primary mechanism for the Payne effect is mainly involved in the nature of the entanglement network in rubbery matrix. It is believed there exists a cooperation between the breakdown and reformation of the filler network and the molecular disentanglement, resulting in enhancing the Payne effect and improving the mechanical hysteresis at high strain amplitudes. Moreover, the vertical and the horizontal shift factors for constructing the master curves could be well understood on the basis of the reinforcement factor f(φ) and the strain amplification factor A(φ), respectively. The surface modification of SiO₂ causes a decrease in f(φ), which is ascribed to weakeness of the filler–filler interaction and improvement of the filler dispersion. However, the surface nature of SiO₂ hardly affects A(φ). © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2594‐2602, 2007     

Structure and properties of styrene-butadiene rubber (SBR) with pyrolytic and industrial carbon black

To evaluate the performance of pyrolytic carbon black (pCB), we filled styrene-butadiene rubber (SBR) with pCB and N330 industrial carbon black (CB). We used two ratios of pCB and N330: 1/9 and 1/1. N330 was selected because its specific surface area was close to that of pCB. The overall CB content in the mixes was 0, 30, 45 and 60 part per hundred rubber (phr). We studied the effects of types and amounts of CB on the dispersion, cure behavior, dynamic mechanical thermal behavior, tensile mechanical and fracture mechanical properties of the filled rubbers. Dispersion of pCB was poorer than that of N330 CB. With respect to tensile mechanical properties – except tear strength – N330 outperformed pCB. The tear strength and fracture mechanics characteristics (J-integral at crack tip opening, and trouser tear strength) of SBR were higher with pCB than with N330. This can be attributed to the broader dispersion of pCB than N330. The combined use of N330 and pCB resulted in intermediate values, reflecting the actual N330/pCB ratio for all measured parameters. We wanted to correlate the mechanical performance with the apparent molecular weight between crosslinks (M_c), and found reasonable correlations for the Payne effect, tensile strength and critical J-integral. On the other hand, we only found a tendency for tear characteristics; this was ascribed to additional effects of (p)CB dispersion.     

Influence of Carbon Black and Silica Filler on the Rheological and Mechanical Properties of Natural Rubber Compound

Rubber compounds are reinforced with fillers such as carbon black and silica. In general, filled rubber compounds shows smooth rheological behavior and mechanical properties. Variation in rheological behavior and mechanical properties was studied in terms of the filler composition using natural rubber compounds filled with both carbon black and silica CB/Si = 0/60, 20/40, 30/30, 40/20 and 60/0 phr (parts per hundred rubber is parts of any non-rubbery material per hundred parts of raw gum elastomer (rubbery material)). The rheological behaviour can be showed in measurement of Mooney viscosity and cure time. The Mooney viscosity of rubber compounds increase with the increasing the carbon black in the compounds. The compound filled with CB/Si of 30/30 and 60/0 showed abnormal rheological behaviour in which the cure time decreased suddenly and the increased at certain ratio during the measurement. The mechanical properties such as hardness, abrasion resistance and tensile stress at 300% elongation were studied. In the hardness and abrasion resistance measurement, the higher ratio CB/Si decrease contribution of silica, which resulting smaller of hardness value. Ratio CB/Si 40/20 gives an optimum filler blended. It is also clearly understood that higher abrasion resistance mainly due to the lower hardness value under the same condition. The tensile stress at 300% elongation of rubber compound increased with the increasing carbon black filler.     

Determination of bound rubber composition of filled SBR/BR blend compounds by analysis of the unbound rubber composition and bound rubber content

Analytical method for determination of the bound rubber composition of a filled SBR/BR blend compound was developed using measurement of the bound rubber content and microstructural analysis of the unbound rubber composition. Various filled SBR/BR blend compounds with different blend ratios were prepared using SBRs with different microstructures. This method included measurement of the bound rubber content, extraction of the unbound rubber, microstructural analysis of the unbound rubber composition, and process for determination of the bound rubber composition. Composition of the unbound rubber was analyzed using liquid proton nuclear magnetic resonance spectroscopy (H-NMR) and transmission Fourier transform infrared spectroscopy (FTIR). It was found that the analytical results using H-NMR had less experimental errors than those using transmission-FTIR. The raw SBR/BR blends were also analyzed in order to evaluate level of the experimental errors. Average SBR/BR ratios of the unbound rubbers were obtained using the 1,2- and 1,4-unit contents determined by the H-NMR analysis. The bound rubber compositions were obtained using the bound rubber contents and the average unbound rubber compositions. It was found that most of the bound rubbers had higher SBR ratios than the formulation value.     

Structure and properties of star‐shaped solution‐polymerized styrene‐butadiene rubber and its co‐coagulated rubber filled with silica/carbon black‐I: morphological structure and mechanical properties

The morphological structure and mechanical properties of the star‐shaped solution‐polymerized styrene‐butadiene rubber (SSBR) and organically modified nanosilica powder/star‐shaped SSBR co‐coagulated rubber (N‐SSBR) both filled with silica/carbon black (CB) were studied. The results showed that, compared with SSBR, silica powder could be mixed into N‐SSBR much more rapidly, and N‐SSBR/SiO₂ nanocomposite had better filler‐dispersion and processability. N‐SSBR/SiO₂/CB vulcanizates displayed higher glass‐transition temperature and lower peak value of internal friction loss than SSBR/SiO₂/CB vulcanizates. In the N‐SSBR/SiO₂/CB vulcanizates, filler was dispersed in nano‐scale resulting in good mechanical properties. Composites filled with silica/CB doped filler exhibited more excellent mechanical properties than those filled with a single filler because of the better filler‐dispersion and stronger interfacial interaction with macromolecular chains. N‐SSBR/SiO₂/CB vulcanizates exhibited preferable performance in abrasion resistance and higher bound rubber content as the blending ratio of silica to CB was 20:30. Copyright © 2008 John Wiley & Sons, Ltd.     

Understanding the reinforcement and dissipation of natural rubber compounds filled with hybrid filler composed of carbon black and silica

The performance of reinforced rubber compounds depends on the filler composition while the reinforcement and dissipation mechanisms still remain unclear.Herein linear and nonlinear dynamic rheological responses of carbon black/silica hybrid filler filling nature rubber compounds are investigated.The rheological contributions of dynamically retarded bulk phase and filler network are revealed to be crucial at high and low frequencies,respectively,and the bulk phase is shown to be of vital importance for the occurrence of nonlinear Payne effect at mediate frequencies.A framework for simultaneously solving reinforcement and dissipation varying with filler composition and content is suggested,providing a new perspective in understanding the filling effect for manufacturing high-performance rubber materials.     

Difference in bound rubber formation of silica and carbon black with styrene‐butadiene rubber

Formation of bound rubber is affected by the physical structure and surface chemistry of filler and the property of rubber. Variation of the bound rubber formation in styrene‐butadiene rubber compounds filled with silica and/or carbon black was studied. Influence of temperature on extraction of loosely bound rubber was also investigated. For the both silica and carbon black‐filled compounds, the bound rubber content increases with increase in the silica content ratio. The bound rubber content decreases with increasing the extracting temperature. The loosely bound rubber content of the silica‐filled compound is higher than that of the carbon black‐filled one. Activation energy for the extraction of the unbound and loosely bound rubbers becomes higher as the total filler content increases. The activation energy of the silica‐filled compound is higher (almost double the value) than for the carbon black‐filled one. Copyright­© 2002 John Wiley & Sons, Ltd.     

橡胶-填料相互作用对丁苯橡胶/白炭黑复合材料性能的影响

本文研究了硅烷偶联剂原位改性白炭黑对溶聚丁苯橡胶(SSBR)性能的影响,结果表明,通过哈克转矩流变仪对含有偶联剂的SSBR/白炭黑混炼胶进行原位热处理后可明显减弱混炼胶的Payne效应,改善白炭黑在橡胶基体中的分散.原位热处理方法能够明显提高硫化胶的300%定伸应力,降低动态压缩温升,同时可使硫化胶在0℃附近具有较高的损耗因子(tanδ),60℃附近具有较低的tanδ.对不同聚合方式得到的丁苯橡胶,即溶聚丁苯橡胶与乳聚丁苯橡胶(ESBR)/白炭黑复合材料的力学性能及动态力学性能进行了研究,结果表明,白炭黑在SSBR2305中分散效果优于在ESBR1502中;采用偶联剂原位改性白炭黑可以使SSBR2305硫化胶获得与ESBR1502硫化胶相当的物理机械性能,更理想的动态力学性能,从而得到力学性能、抗湿滑性、滚动阻力及耐磨性更加均衡的理想轮胎材料.通过对具有不同偶联效率的SSBR/白炭黑体系的微观结构与性能研究发现,随偶联效率的增加,其结合橡胶含量增加,Payne效应减弱;高偶联效率的S-SBR具有较低的动态压缩温升及较好的耐磨性.     

Influence of filler type and content on properties of styrene‐butadiene rubber (SBR) compound reinforced with carbon black or silica

Rubber compounds are filled with reinforcing fillers to improve their physical properties. Carbon black and silica have different surface chemistries to each other. Differences in properties of carbon black‐ and silica‐reinforced styrene‐butadiene rubber (SBR) compounds were studied. Variation of properties of carbon black‐ or silica‐filled compounds with the filler content was also investigated. The silica‐filled compounds without any coupling agent and dispering agent were prepared to investigate the influence of polar materials‐adsorption on the silica surface. Viscosity and crosslink density increased with increase of the filler content. Hardness, modulus, tensile strength, and wear property were improved more and more by increasing the filler content. Viscosity of the silica‐filled compound was higher than that of the carbon black‐filled one. Cure rate of the silica‐filled compound became slower as the filler content increased, while that of the carbon black‐filled one became faster. Difference in properties between the carbon black‐ and silica‐filled compounds were explained by the poor silica dispersion and the adsorption of cure accelerator on the silica surface. Copyright © 2004 John Wiley & Sons, Ltd.     

Synergistic effect by high specific surface area carbon black as secondary filler in silica reinforced natural rubber tire tread compounds

The partial replacement of silica by high specific surface area and high structure Carbon Black (CB) N134 as secondary filler, keeping the same total filler content at 55 phr, shows a clear synergistic effect on overall performance. At low content of CB, i.e. in the range of 0–36 wt% of CB relative to total filler amount, the Payne effect and tan delta at both 0 °C and 60 °C change marginally, but thereafter gradually increase. Cure times are shortened in the presence of CB, facilitating an increase of productivity. Bound rubber content and mechanical properties show an optimum at 18 wt% of CB relative to total filler amount or at a ratio of silica/CB 45/10 phr. With regard to tire performance as indicated by the laboratory test results, the abrasion resistance, wet grip and ice traction can therefore be enhanced while maintaining the tire rolling resistance at the optimum level for this silica/CB ratio.     

Polymer-Filler Interphase Dynamics and Reinforcement of Elastomer Nanocomposites

The effect of polymer-filler interaction on interphase dynamics between filler particles in elastomer nanocomposites and the mechanisms of rubber reinforcement by carbon black (CB) are investigated with different techniques. To determine how polymer-filler interface influences the properties of the system, CB black was modified with the ionic liquid (IL) 1-allyl-3-methylimidazolium chloride (AMIC) and mixed with different, more or less, polar elastomers. For typical diene-elastomers (EPDM, SBR), this modification leads to a decreased polymer-filler coupling strength due to the coverage of active sites at the CB surface by AMIC. This is demonstrated by evaluating the energy site distribution from static gas adsorption isotherms with the polymer analogues gas 1-Butene. However, an improvement of polymer filler coupling was determined in the case of saturated, polar rubbers (HNBR) due to attractive dipolar interactions between the polar units of the polymer and the strongly adsorbed IL at the CB surface. The different couplings affect the polymer-filler interphase dynamics between filler particles, which determines the properties of the filler network and filler-filler bonds. To describe the effect of CB surface modification quantitatively, the Dynamic Flocculation Model (DFM) has been used to calculate polymer- and filler-specific material parameters from cyclic stress-strain measurements. The fitted data deliver a coherent picture of filler-filler- and polymer-filler couplings showing a characteristic dependence on rubber polarity. A confirmation of the effect of surface modification on the strength of filler-filler bonds is obtained by nonequilibrium molecular dynamics (MD) simulations of bond rupture under tension. They also provide indications for a glassy-like behavior of strongly confined polymer layers between attractive walls.     

Understanding the effect of filler shape induced immobilized rubber on the interfacial and mechanical strength of rubber composites

Styrene butadiene rubber (SBR) composites with silica, halloysite nanotubes (HNTs) and montmorillonite (MMT) were prepared and the interfacial and mechanical properties were compared to understand the reinforcing behaviours of these fillers based on the results of SEM, DSC, DMA, etc. Due to the formation of interparticle domain, HNTs immobilized more rubber approaching their surface than silica and MMT. Interestingly, only tightly immobilized rubber chains made contribution to the enhancement of interfacial and mechanical strength of SBR composites. This was because the tightly immobilized rubber acted as a bridge in the filler-rubber interface and induced the formation of stretched rubber chains linked filler network when the composites were loaded in tension, while loosely immobilized rubber were easy to slip off from filler surface, causing the separation between filler and bulk rubber. Therefore, silica with more tightly immobilized rubber approaching its surface showed better reinforcing effect on rubber than HNTs and MMT.     

Open spaces and molecular motions in carbon‐black‐ and silica‐loaded SBR investigated using positron annihilation

Lifetime spectra of positrons were measured for styrene–butadiene rubber (SBR) vulcanizates filled with carbon black (CB) or silica. At temperatures between 10 and 420 K, no large difference between the size of the open spaces in the CB/SBR vulcanizate and that in the specimen without the filler was observed. Above the glass‐transition temperature (T_g = 230 K), the same was true for the silica/SBR vulcanizate. Below T_g, however, the size of the open spaces was reduced by the incorporation of silica as a result of the suppression of local molecular motions in the SBR. The density of the open spaces was reduced by the incorporation of the fillers. However, above 400 K it started to increase in the silica/SBR vulcanizate. For the CB/SBR vulcanizate, the introduction of open spaces was well suppressed, even at 420 K. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 835–842, 2001     

纳米微晶纤维素对炭黑补强天然橡胶力学性能和动态性能的影响

采用酸水解工业微晶纤维素(MCC)制备纳米微晶纤维素(NCC),将其与天然胶乳共凝沉,混炼时加入炭黑(CB),制备了天然橡胶(NR)/NCC/CB复合材料,研究了NR/NCC/CB和NR/NCC/CB/RH(间苯二酚-六亚甲基四胺络合物)复合材料的力学性能和动态性能,并与NR/CB体系的性能进行对比.结果表明NCC可以均匀分散在天然橡胶基体中,且依拉伸方向取向,随着NCC替代炭黑的份数增加,Payne效应减弱,说明NCC本身并不构成强的填料网络,NR/NCC/CB与NR/CB比较,前者整体的网络化程度减弱,体系的损耗因子变化不大,NCC的加入改善了NR/CB的力学性能和抗屈挠龟裂性能,降低压缩疲劳温升和压缩永久形变,当NCC取代5～20 phr CB后,仍然保持高耐磨炭黑补强天然橡胶的耐磨耗性能.动态力学性能显示NR/NCC/CB的玻璃化转变温度较NR/CB变化不大,0℃的tanδ略有下降的同时60℃的tanδ明显降低.NR/NCC/CB/RH体系的Payne效应较NR/NCC/CB明显减弱,力学性能、抗屈挠龟裂性能和耐磨耗性能进一步改善,体系的压缩疲劳温升和压缩永久形变更小.     

Improvement of properties of silica-filled styrene-butadiene rubber (SBR) compounds using acrylonitrile-styrene-butadiene rubber (NSBR)

Since silica has strong filler–filler interactions and adsorbs polar materials, a silica-filled rubber compound wil have poor dispersion of the filler and a poor cure characteristic. Improvement of properties of silica-filled styrene-butadiene rubber (SBR) compounds has been studied using emulsion SBR-based acrylonitrile-styrene-butadiene rubber (NSBR). The silica dispersion is improved by adding NSBR to the compound. The bound rubber content increases with increase in the NSBR content. The scorch time and cure rate become faster as the NSBR content increases. The crosslink density also increases by increasing the NSBR content. The wear property is improved by adding the NSBR. Copyright © 2003 John Wiley & Sons, Ltd.     

Influence of Liquid Isoprene Rubber on Strain Softening of Carbon Black Filled Isoprene Rubber Nanocomposites

The reinforcement of rubbers by nanoparticles is always accompanied with enhanced dissipation of mechanical energy upon large deformations. Methods for solving the contradiction between improving reinforcement and reducing energy dissipation for rubber nanocomposites have not been well developed. Herein carbon black(CB) filled isoprene rubber(IR)/liquid isoprene rubber(LR) blend nanocomposites with similar crosslink density(ν_e) are prepared and influence of LR on the strain softening behaviors including Payne effect under large amplitude shear deformation and Mullins effect under cyclic uniaxial deformation is investigated. The introduction of LR could improve the frequency sensitivity of loss modulus and reduce critical strain amplitude for Payne effect and loss modulus at the low amplitudes.Meanwhile, tuning ν_e and LR content allows reducing mechanical hysteresis in Mullins effect without significant impact on the mechanical performances. The investigation is illuminating for manufacturing nanocomposite vulcanizates with balanced mechanical hysteresis and reinforcement effect.