Influence of ionic liquid on the polymer–filler coupling and mechanical properties of nano‐silica filled elastomer

The natural rubber (NR) nanocomposites were fabricated by filling ionic liquid (1‐allyl‐3‐methyl‐imidazolium chloride, AMI) modified nano‐silica (nSiO₂) in NR matrix through mechanical mixing and followed by a cure process. Based on the measurements of differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), solid state nuclear magnetic resonance spectroscopy, and Raman spectroscopy, it was proved that AMI could interact with nSiO₂ through hydrogen bonds. With the increase of AMI content, the curing rate of nSiO₂/NR increased. The results of bound rubber and dynamic mechanical properties showed that polymer–filler interaction increased with the modification of nSiO₂. Morphology studies revealed that modification of nSiO₂ resulted in a homogenous dispersion of nSiO₂ in NR matrix. AMI modified nSiO₂ could greatly enhance the tensile strength and tear strength of nSiO₂/NR nanocomposites. Compared to unmodified nSiO₂/NR nanocomposite, the tensile strength of AMI modified nSiO₂/NR nanocomposite increased by 102%. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44478.     

Synergistic effect of carbon black and carbon–silica dual phase filler in natural rubber matrix

In this article, the synergistic effects of carbon black (CB) and modified carbon–silica dual phase filler (MCSDPF) on the properties of natural rubber (NR) were investigated. MCSDPF was prepared by modifying carbon–silica dual phase filler (CSDPF) with bis(3‐triethoxysilylpropyl)tetrasulphane (Si‐69). Fourier transform infrared spectroscopy and thermogravimetric analyzer analyses revealed that Si‐69 was successfully grafted to CSDPF. NR‐based compounds containing various combinations of MCSDPF and CB were prepared through a mechanical mixing. Investigations of mechanical properties, ageing resistance, abrasion resistance, dynamic mechanical properties, and morphology of tear fractured surface of MCSDPF/CB/NR vulcanizates were conducted. Our study shows that adding MCSDPF led to significant improvement in the tear resistance, fatigue life, and elongation at break of MCSDPF/CB/NR vulcanizates. Optimum stoichiometric combination of MCSDPF and CB inside the NR matrix was derived (ratio of MCSDPF and CB in wt% = 15/50), which showed synergistic effects of MCSDPF upon CB that was ultimately reflected in their tensile strength, wet skid resistance, and rolling resistance. POLYM. COMPOS., 35:1466–1472, 2014. © 2013 Society of Plastics Engineers     

New approach for preparation of dry natural rubber nanocomposites through acid‐free co‐coagulation: Effect of organoclay content

Natural rubber (NR) vulcanizates exhibit good mechanical properties compared to vulcanizates of synthetic rubbers. Incorporation of a conventional filler at higher loadings to NR enhances its modulus, while reduction in tensile strength and elongation. This paper presents a new strategy for development of a NR‐clay nanocomposite with enhanced mechanical properties by incorporation of lower loadings (2–8 phr) of cetyl trimethyl ammonium bromide modified montmorillonite clay (OMMT‐C) under acid‐free environment. The effect of OMMT‐C loading on cure characteristics, rubber‐filler interactions, crosslink density, dynamic mechanical thermal properties, and mechanical properties were evaluated. Incorporation of OMMT‐C accelerated the vulcanization process and enhanced mechanical properties. X‐ray diffraction analysis and scanning electron microscopy images revealed that the formation of intercalated clay structures at lower OMMT‐C loadings, and clay aggregates at higher loadings. A nanocomposite at OMMT‐C loading of 2 phr exhibited the best balanced mechanical properties, and was associated with highest crosslink density and rubber–filler interactions. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46502.     

Fatigue resistance of silica‐filled natural rubber vulcanizates: comparative study of the effect of phosphorylated cardanol prepolymer and a silane coupling agent

The fatigue resistance of silica‐filled natural rubber (NR) mixes modified with phosphorylated cardanol prepolymer (PCP) was studied in comparison with similar compositions without PCP and with those containing the same dosage of a silane coupling agent (Si‐69). Considerable improvement in the fatigue resistance was observed for the PCP‐modified NR vulcanizate containing 20 phr of silica compared with the unmodified and Si‐69 modified vulcanizates. In addition, the tear strength of the PCP‐modified NR vulcanizate was higher than that of the others. Atomic force microscopy and the scanning electron microscopy of the vulcanizates showed better dispersion of silica particles in the NR matrix in the presence of PCP than in the unmodified and Si‐69‐modified NR vulcanizates. It is assumed that, at a dosage of 5 phr, PCP functions as a coupling agent between NR and the silica particles thereby improving the filler dispersion and consequently the mechanical properties of the vulcanizate. Copyright © 2005 Society of Chemical Industry     

Cardanol grafted natural rubber: A green substitute to natural rubber for enhancing silica filler dispersion

Natural rubber (NR) usage is wide‐spread from pencil erasers to aero tyres. Carbon black and silica are the most common reinforcing fillers in the rubber industries. Carbon black enhances the mechanical properties, while silica reduces the rolling resistance and enhances the wet grip characteristics. However, the dispersion of polar silica fillers in the nonpolar hydrocarbon rubbers like natural rubber is a serious issue to be resolved. In recent years, cardanol, an agricultural by‐product of the cashew industry is already established as a multifunctional additive in the rubber. The present study focuses on dispersion of silica filler in natural rubber grafted with cardanol (CGNR) and determination of its technical properties. The optimum cure time reduces and the cure rate increases for the CGNR vulcanizates as compared to that of the NR vulcanizates at all loadings of silica varying from 30 to 60 phr. The interaction between the phenolic moiety of cardanol and the siloxane as well as silanol functional groups present on the silica surface enhances the rubber–filler interaction which leads to better reinforcement. The crosslink density and bound rubber content are found to be higher for the silica reinforced CGNR vulcanizates. The physico‐mechanical properties of the silica reinforced CGNR vulcanizates are superior to those of the NR vulcanizates. The CGNR vulcanizates show lower compression set and lower abrasion loss. The dynamic‐mechanical properties exhibit less Payne effect for silica reinforced CGNR vulcanizates as compared to the NR vulcanizates. The transmission electron photomicrographs show uniform dispersion of silica filler in the CGNR matrix. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43057.     

Effect of carbon black/nanoclay hybrid filler on the dynamic properties of natural rubber vulcanizates

In this study, natural rubber (NR) nanocomposites based on carbon black (CB) and two poly(ethylene glycol) (PEG)‐modified clay hybrid filler were fabricated. The morphology and mechanical properties were studied. The dynamic properties of NR vulcanizates were investigated over a range of strain amplitude at two temperatures. It was found that NR with hybrid filler exhibits superior mechanical properties over that with CB as single phase filler. The hybrid filler causes a significant alteration in the dynamic properties of rubber. The Payne effect becomes more pronounced in rubber with modified clay. A decrease in loss factor (tanδ) was observed for rubber with hybrid filler also. The results revealed that the inclusion of nanoclay (NC) could induce a stronger and more developed filler network. Because of the anisotropy of the nanolayers, NC would depress the reconstruction of filler network, or lower the reformation rates when broken down under deformation, giving rise to lower tanδ value at broad temperature range as well as strain amplitude. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Role of lignin filler in stabilization of natural rubber–based composites

The stabilizing effect of a natural filler, sulfur‐free lignin, on the thermal degradation of natural rubber (NR) was examined. Lignin was incorporated into NR in amounts of 10–30 phr (parts per hundred parts of rubber). It was shown that the lignin preparation used improved the physicomechanical properties of the rubber vulcanizates. Thermogravimetric analysis and differential scanning calorimetry were used to study the thermal degradation of unfilled and lignin‐filled vulcanized natural rubber. Measurements were carried out under atmospheric conditions. It was revealed that lignin used as filler increased the resistance of NR vulcanizates to thermooxidative degradation in air. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1226–1231, 2007     

Fly ash particles and precipitated silica as fillers in rubbers. I. Untreated fillers in natural rubber and styrene–butadiene rubber compounds

In this study, we investigated the effects of untreated precipitated silica (PSi) and fly ash silica (FASi) as fillers on the properties of natural rubber (NR) and styrene–butadiene rubber (SBR) compounds. The cure characteristics and the final properties of the NR and SBR compounds were considered separately and comparatively with regard to the effect of the loading of the fillers, which ranged from 0 to 80 phr. In the NR system, the cure time and minimum and maximum torques of the NR compounds progressively increased at PSi loadings of 30–75 phr. A relatively low cure time and low viscosity of the NR compounds were achieved throughout the FASi loadings used. The vulcanizate properties of the FASi‐filled vulcanizates appeared to be very similar to those of the PSi‐filled vulcanizates at silica contents of 0–30 phr. Above these concentrations, the properties of the PSi‐filled vulcanizates improved, whereas those of the FASi‐filled compounds remained the same. In the SBR system, the changing trends of all of the properties of the filled SBR vulcanizates were very similar to those of the filled NR vulcanizates, except for the tensile and tear strengths. For a given rubber matrix and silica content, the discrepancies in the results between PSi and FASi were associated with filler–filler interactions, filler particle size, and the amount of nonrubber in the vulcanizates. With the effect of the FASi particles on the mechanical properties of the NR and SBR vulcanizates considered, we recommend fly ash particles as a filler in NR at silica concentrations of 0–30 phr but not in SBR systems, except when improvement in the tensile and tear properties is required. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2119–2130, 2004     

Natural rubber vulcanizate reinforced by modified coal‐shale‐based fillers

Coal shale is considered a waste material in coal mining and washing processes. It comprises both inorganic and organic components. In this study, two kinds of coal shale were microcracked, burned, modified by enoxidation natural rubber (ENR), and then used as reinforcing fillers for natural rubber (NR). The NR vulcanizates reinforced with this modified filler were characterized by bounded rubber content, apparent crosslink density, and various mechanical property tests. The results show that the ultramicro coal‐shale powder was a good filler for NR. It could be mixed quickly, and it dispersed well in NR, which resulted in a significant enhancement. After modification by ENR, the reinforcement properties were improved further. The results suggest that this new type of filler could be used as a semireinforcing filler to replace or partially replace carbon black. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1397–1400, 2004     

Effect of organoclay loading level on mechanical properties,thermomechanical behavior,and heat build‐up of natural rubber/organoclay nanocomposites

Sodium‐montmorillonite nanoclay was modified with octadecylamine and compounded with natural rubber (NR) by dry mixing method. The effects of organoclay loading level on mechanical properties, thermal–mechanical behavior, and heat build‐up of NR/organoclay nanocomposites were investigated. Temperature scanning stress relaxation technique was used to characterize the thermal–mechanical behavior of the composites. The morphological properties were assessed by X‐ray diffraction and transmission electron microscopy. Loading levels of organoclay below 5 phr gave improved mechanical properties and heat build‐up, along with exfoliated clay structure in the nanocomposites. On the other hand, with loading levels above 7 phr the organoclay tended to agglomerate, and X‐ray diffraction revealed an intercalated structure. In these cases, the excess residual organoclay caused significantly increased stress relaxation and heat build‐up. Unmodified sodium‐montmorillonite as filler did not significantly affect the mechanical and heat build‐up properties of NR vulcanizates. POLYM. COMPOS., 37:1735–1743, 2016. © 2014 Society of Plastics Engineers     

环氧化天然橡胶共交联改性EPDM/NR共混物的性能

将三元乙丙橡胶(EPDM)与环氧化天然橡胶(ENR)共交联改性后,再与天然橡胶(NR)共混,考察了ENR共交联改性EPDM/NR共混胶的硫化特性、硫化胶的物理机械性能、溶胀指数和耐热空气老化性能,并对该硫化胶进行了差示扫描量热分析。结果表明,EPDM经过ENR共交联改性后与NR共混,ENR共交联改性EPDM/NR共混胶的交联程度明显提高,各相达到了同步交联,硫化胶的综合性能得到了显著改善。     

On the potential of organoclay with respect to conventional fillers (carbon black,silica) for epoxidized natural rubber compatibilized natural rubber vulcanizates

Onium modified montmorillonite (organoclay) was compounded with natural rubber (NR) in an internal mixer and cured by using a conventional sulfuric system. Epoxidized natural rubber with 50 mol % epoxidation (ENR 50) in 10 parts per hundred rubber (phr) was used as a compatibilizer in this study. For comparison purposes, two commercial fillers: carbon black (grade N330) and silica (grade vulcasil‐S) were used. Cure characteristics were carried out on a Monsanto MDR2000 Rheometer. Organoclay filled vulcanizate showed the lowest values of torque maximum, torque minimum, scorch, and cure times. The kinetics of cure reaction showed organoclay could behave as a cocuring agent. The mechanical testing of the vulcanizates involved the determination of tensile and tear properties. The improvement of tensile strength, elongation at break, and tear properties in organoclay filled vulcanizate were significantly higher compared to silica and carbon black filled vulcanizates. In terms of reinforcing efficiency (RE), organoclay exhibited the highest stiffness followed by silica and carbon black filled vulcanizates. Scanning electron microscopy revealed that incorporation of various types of fillers has transformed the failure mechanism of the resulting NR vulcanizates compared to the gum vulcanizates. Dynamic mechanical thermal analysis (DMTA) revealed that the stiffness and molecular relaxation of NR vulcanizates are strongly affected by the filler–rubber interactions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2438–2445, 2004     

Mechanical and dynamic mechanical properties of rice husk ash–filled natural rubber compounds

A laboratory‐sized two‐roll mill was used to incorporate rice husk ash into natural rubber (NR). A conventional vulcanization system was used for curing and cure studies were carried out on a Monsanto rheometer. Physical testing of the NR vulcanizates involved determining tensile and tear resistances and hardness. Swelling behavior of NR compounds and scanning electron microscopy were used to investigate the interaction between rice husk ash and natural rubber. Also, dynamical mechanical thermal analysis was used to assess filler–rubber interactions in terms of storage modulus (E′) and loss tangent (tan δ). For comparison purposes, two commercial fillers, precipitated silica (Zeosil‐175) and carbon black (N774), were also used. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2331–2346, 2002     

Natural rubber–ethylene‐propylene‐diene rubber covulcanization: Effect of reinforcing fillers

Filled covulcanizates of elastomer blend comprising natural rubber (NR) and ethylene‐propylene‐diene rubber (EPDM) of commercial importance were successfully prepared by using a multifunctional rubber additive; namely, bis(diisopropyl)thiophosphoryl disulfide (DIPDIS). A Two‐stage vulcanization technique further improved the physicochemical properties of the blend vulcanizates by restricting, through the formation of polar rubber bound intermediates, the migration of curative and filler from lower to highly unsaturated rubber. Scanning electron microscopy studies indicate homogeneity and coherency in the morphology of the two‐stage vulcanizates. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1001–1010, 2002; DOI 10.1002/app.10361     

Interfacial Interactions of Silica and Natural Rubber Enhanced by Hydroxyl Telechelic Natural Rubber as Interfacial Modifier

The incompatibility between hydrophilic silica and hydrophobic rubber is an important problem on using silica in nonpolar rubber. In this study, hydroxyl telechelic natural rubber (HTNR) that contains hydroxyl‐terminated groups was introduced into silica‐reinforced natural rubber (NR) in order to improve the bonding strength between rubber and silica. The properties of silica‐reinforced NR compounds and vulcanizates as a function of varying silica contents were evaluated at a fixed HTNR concentration at 8% wt/wt of silica content. The results show that the improvement of silica dispersion and decreasing of filler–filler interactions (Payne effect) were obtained in the NR compounds and vulcanizates with HTNR addition. The enhancements in tensile properties, crosslink density, abrasion resistance, heat build‐up, and thermal properties of the silica‐reinforced NR vulcanizates with added HTNR confirmed that HTNR performed good as interfacial modifier of silica. In the study, the optimum properties of silica‐reinforced NR vulcanizate were achieved at 30 phr silica with 2.4 phr HTNR. However, HTNR still showed poorer efficiency than the synergy between commercial silane coupling agent, bis [3‐(triethoxysilyl) propyl] tetrasulphide (TESPT) and diphenylguanidine (DPG) when used in silica‐reinforced NR vulcanizate. J. VINYL ADDIT. TECHNOL., 26:291–303, 2020. © 2019 Society of Plastics Engineers     

Studies on blends of natural rubber and ethylene propylene diene rubber modified with phosphorylated cardanol prepolymer: Processability,physico‐mechanical properties,and morphology

The melt processability and physico‐mechanical properties of blends of natural rubber (NR) and ethylene propylene diene rubber (EPDM) containing different dosages (0–10 phr) of phosphorylated cardanol prepolymer (PCP) were studied in unfilled and china‐clay‐filled mixes. The plasticizing effect of PCP in the blends was evidenced by progressive reduction in power consumption of the mixing and activation energy for melt flow with an increase in the dosage of PCP. The PCP‐modified blend vulcanizates showed higher tensile properties and tear strength despite a decrease in the chemical crosslink density (CLD) index. This is presumably due to the formation of a crosslinked network structure of PCP with the rubbers and improved dispersion of the filler particles in the rubber matrix, as evidenced by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Thermogravimetric analysis showed an increase in thermal stability of the blend vulcanizate in presence of 5 phr of PCP. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5123–5130, 2006     

甲基丙烯酸固态原位接枝改性炭黑对天然橡胶和顺丁橡胶性能的影响

考察了固态原位接枝改性制备的甲基丙烯酸接枝改性炭黑对天然橡胶(NR)和顺丁橡胶。(BR)静态力学性能、动态力学性能的影响。结果表明。甲基丙烯酸改性炭黑比普通商品炭黑填充的NR硫化胶具有更好的静态力学性能;甲基丙烯酸改性炭黑曼有利于降低NR和BR硫化胶的滚动阻力。同时,有利于提高NR硫化胶的抗湿滑性。     

Research on Payne effect of natural rubber reinforced by graft‐modified silica

Silica (SiO₂) modified by in situ solid‐phase grafting was used for natural rubber (NR) reinforcement. The physical mechanical properties and Payne effect of natural rubber reinforced by SiO₂ and graft‐modified silica (G‐SiO₂) were analyzed systematically. The results showed the comprehensive performance of NR/G‐SiO₂ was better than that of NR/SiO₂. There was a proportional relationship between the filler loading and Payne effect. NR/G‐SiO₂ presented weaker Payne effect in comparison with NR/SiO₂. A qualitative analysis on the correlation of filler 3D network structure and filler loading was carried out according to the relationship between the bound rubber content and the shear modulus. The Payne effect mechanisms of rubber compounds differed according to the different filler loading. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43891.     

Influence of polymer–filler interactions on retraction behaviors of natural rubber vulcanizates reinforced with silica and carbon black

In general, silica‐filled rubber compounds contain a silane coupling agent to improve the filler dispersion and polymer–filler interactions. The silane coupling agent modifies the silica surface and makes crosslinks between the rubber and the silica. Influence of the modification of silica on the retraction behaviors of natural rubber (NR) vulcanizates reinforced with silica and carbon black was studied. Variation of the retraction behaviors of NR vulcanizates with filler composition was also investigated. The vulcanizates containing the silane coupling agent were recovered faster than those without the silane coupling agent. The recovery difference between the vulcanizates without and with the silane coupling agent increased with increased silica content. For the vulcanizates containing the silane coupling agent, the retraction behaviors were nearly the same, irrespective of filler composition. But, for the vulcanizates without the silane coupling agent, the vulcanizate was recovered more and more slowly as the silica content increased. The experimental results are explained with the polymer–filler interactions, modification of silica surface, and formation of crosslinks between silica and rubber. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 691–696, 2006     

炭黑对橡胶增强机理的研究现状

介绍了目前炭黑增强橡胶的一些理论,如分子链滑动理论、结合胶理论、填料网络理论、炭黑表面结构理论和范德华网络理论,分析了这些理论存在的合理性与局限性,指出了橡胶增强理论新的研究方向。