Effect of carbon nanofibers on mechanical and electrical behaviors of acrylonitrile‐butadiene rubber composites

Recently, carbon nanofibers have become an innovative reinforcing filler that has drawn increased attention from researchers. In this work, the reinforcement of acrylonitrile butadiene rubber (NBR) with carbon nanofibers (CNFs) was studied to determine the potential of carbon nanofibers as reinforcing filler in rubber technology. Furthermore, the performance of NBR compounds filled with carbon nanofibers was compared with the composites containing carbon black characterized by spherical particle type. Filler dispersion in elastomer matrix plays an essential role in polymer reinforcement, so we also analyzed the influence of dispersing agents on the performance of NBR composites. We applied several types of dispersing agents: anionic, cationic, nonionic, and ionic liquids. The fillers were characterized by dibutylphtalate absorption analysis, aggregate size, and rheological properties of filler suspensions. The vulcanization kinetics of rubber compounds, crosslink density, mechanical properties, hysteresis, and conductive properties of vulcanizates were also investigated. Moreover, scanning electron microscopy images were used to determine the filler dispersion in the elastomer matrix. The incorporation of the carbon nanofibers has a superior influence on the tensile strength of NBR compared with the samples containing carbon black. It was observed that addition of studied dispersing agents affected the performance of NBR/CNF and NBR/carbon black materials. Especially, the application of nonylphenyl poly(ethylene glycol) ether and 1‐butyl‐3‐methylimidazolium tetrafluoroborate contributed to enhanced mechanical properties and electrical conductivity of NBR/CNF composites.     

Thermal characterization of the effect of fillers and ionic liquids on the vulcanization and properties of acrylonitrile–butadiene elastomer

Different thermal analysis techniques were used to study the effect of fillers and ionic liquids (ILs) on the vulcanization process, thermal and dynamic mechanical properties of acrylonitrile–butadiene elastomer (NBR). The products of the studies were composites of NBR filled with hydrotalcite, nanosized silica or carbon black. ILs such as 1-butyl-1-methylpyrrolidinium (BMpyrrolBF₄), 1-butyl-4-methylpyridinium (BMpyrBF₄) or 1-butyl-1-methylpiperidinium (BMpipBF₄) tetrafluoroborates were applied to improve the dispersion degree of the curatives and filler particles in the elastomer and to increase the efficiency of vulcanization. The differential scanning calorimetry results indicated that ILs reduced the vulcanization temperature of NBR compounds and increased the homogeneity of cross-link distribution in the elastomer network. NBRs filled with carbon black or silica exhibited similar thermal stabilities, whereas hydrotalcite reduced the temperature of thermal decomposition. The lowest mechanical loss factors were determined for vulcanizates filled with nanosized silica.

     

Radiation effect on properties of carbon black filled NBR/EPDM rubber blends

Rubber blend of acrylonitrile butadiene rubber (NBR) and ethylene-propylene diene monomer (EPDM) rubber (50/50) has been loaded with increasing contents, up to 100 phr, of reinforcing filler, namely, high abrasion furnace (HAF) carbon black. Prepared composites have been subjected to gamma radiation doses up to 250 kGy to induce radiation vulcanization under atmospheric conditions. Mechanical properties, namely, tensile strength (TS), tensile modulus at 100% elongation (M₁₀₀), and hardness have been followed up as a function of irradiation dose and degree of loading with filler. On the other hand, variation of the swelling number as a physical property, as a function of same parameters, however, in car oil as well as brake oil has been undertaken. In addition, the electrical properties of prepared composites, namely, their electrical conductivity, were also evaluated. The thermal behavior of the prepared composites was also investigated. The results obtained indicate that improvement has been attained in different properties of loaded NBR/EPDM composites with respect to unloaded ones.     

Study on insulating thermal conductive BN/HDPE composites

Thermal conductivity of boron nitride (BN) reinforced high density polyethylene (HDPE) composites was investigated under a special dispersion state of BN particles in HDPE, i.e., BN particles surrounding HDPE matrix particles. The results indicated that the special dispersion of BN in matrix gives the composites high thermal conductivity at low filler content; moreover, the smaller BN particles can more easily form conductive chains of filler compared to the larger filler particles. Examining the dependence of electrical insulation and mechanical properties of the composites on BN content demonstrated that the reinforced composites containing 30% by volume of filler has good electrical insulation and mechanical properties.     

Cure characteristics and properties of NBR composites filled with co‐precipitates of black liquor and montmorillonite

Acrylonitrile‐butadiene rubber (NBR) composites filled with co‐precipitates of black liquor and montmorillonite (CLM) were prepared by mechanical mixing on a two‐roll mill. The cure characteristics, mechanical properties, thermal properties, and thermo‐oxidative aging properties of NBR/CLM composites were evaluated. Scanning electron microscopy and transmission electron microscopy showed that the filler particles were well dispersed in the NBR/CLM composites. The scorch time and optimum cure time increase with increasing filler loading. A remarkable enhancement in tensile strength, elongation at break, 300% modulus, and shore “A” hardness was also observed. When the loading of CLM was 40 parts per hundred rubbers, it showed about seven times increase in tensile strength, about 1.8 times increase in elongation at break, about three times increase in 300% modulus, and about 1.3 times increase in shore A hardness, respectively, as compared with those of pure cured NBR. Thermal properties and thermal oxidative aging properties, in general, were also improved with loading of this novel filler. Copyright © 2011 John Wiley & Sons, Ltd.     

玻璃纤维对聚甲醛基导电复合材料性能的影响

采用在转矩流变仪中熔融混合的方法制备了聚甲醛(POM)/多壁碳纳米管(MWCNTs)/玻璃纤维(GF)和POM/炭黑(CB)/GF复合材料,研究了GF的加入对复合材料的导电性能、结晶行为和动态力学性能的影响.采用场发射扫描电镜(FESEM)观察了复合材料中导电填料的分散状态,发现GF的加入对MWCNTs和CB的分散状态没有明显影响.虽然GF为导电惰性填料,但因其加入起到了占位作用,明显提高了导电填料的有效浓度,从而使复合材料的体积电阻率明显降低.采用示差扫描量热仪(DSC)研究了复合材料中POM的结晶行为,发现GF的加入对POM的结晶温度、熔点和结晶度均无明显影响.采用动态机械分析仪(DMA)对复合材料的动态力学性能进行了研究,表明GF的加入能够明显地提高复合材料的储能模量.     

Barium Titanate-reinforced Acrylonitrile-Butadiene Rubber: Synergy Effect of Carbon-based Secondary Filler

Acrylonitrile rubber(NBR) composites filled with barium titanate(BT) were prepared using an internal mixer and a two-roll mill. Also, a secondary filler, namely carbon nanotubes(CNT), was added in order to find a potential synergistic blend ratio of BT and CNT. The cure characteristics, tensile and dielectric properties(dielectric constant and dielectric loss) of the composites were determined. It was found that NBR/BT composites with CNT secondary filler, at a proper BT:CNT ratio, exhibited shorter scorch time(t_(s1)) and cure time(t_(c90)) together with superior tensile properties and reinforcement efficiency, relative to the one with only the primary filler. In addition, the NBR/BT-CNT composite with 80 phr BT and 1-2 phr CNT had dielectric constant of 100-500, dielectric loss of 12-100 and electrical conductivity below 10~(-4) S/m together with high thermal stability. Thus, with a proper BT:CNT mix and filler loading, we can produce mechanically superior rubber composites that are easy to process and low-cost, for flexible dielectric materials application.     

Formation of Network by Carbon Black，Silica and Their Mixing Fillers in Isoprene Rubber北大核心CSCD

The network formed by fillers has great influence on the mechanical properties of rubber materials. To understand the formation of network by carbon black,silica,and carbon black/silica mixing fillers in rubber and its influence on the properties of rubber,isoprene rubber/filler composites with different filler loadings are prepared and their micromorphology,rheological and tensile properties are investigated. It is found that the dispersion of fillers is better in rubber after cure than that in rubber before cure for all three rubber systems,and the filler size of silica is smaller than that of carbon black,but the aggregation is more severe in silica filled rubber system. In mixed filler system,the two fillers tend to aggregate separately, leading to the low modulus at small strain than that in single filler system. With the increase of the filler loading,the tensile strength increases first and then decreases,the elongation at break decreases,and the temperature rise in compression flexometer tests increases. Moreover,the temperature rise in mixed filler system is higher than that in single filler system at high filler loading. © 2022, Science Press (China). All rights reserved.     

Incorporation of carbon nanotubes into polyethylene by high energy ball milling: Morphology and physical properties

High energy ball milling (HEBM) was utilized, as an innovative process, to incorporate carbon nanotubes (CNTs) into a polyethylene (PE) matrix avoiding: high temperatures, solvents, ultrasonication, chemical modification of carbon nanotubes. Composites with 1, 2, 3, 5, and 10 wt % of carbon nanotubes were prepared. Films were obtained melting the powders in a hot press. Morphology and physical properties (thermal, mechanical, electrical properties) were evaluated. The used processing conditions allowed to obtain a satisfactory level of dispersion of CNTs into the PE matrix with a consequent improvement of the physical properties of the samples. The thermal degradation was significantly delayed already with 1–2% wt of CNTs. The mechanical properties resulted greatly improved for low filler content (up to 3% wt). The electrical measurements showed a percolation threshold in the range 1–3 wt % of CNTs. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 597–606, 2007     

Tensile,Electrical Conductivity,and Morphological Properties of Carbon Black–Filled Epoxy Composites

This work investigates the effect of carbon black content on the tensile, electrical, and morphological properties of epoxy matrix. Carbon black–filled epoxy composites were obtained by mixing the desired amount of carbon black from bamboo stem (BS-CB), oil palm empty fruit bunch (EFB-CB), and coconut shell (CNS-CB) with the epoxy resin. Tensile and electrical properties of carbon black from three different sources (BS-CB, EFB-CB, and CNS-CB) used to fill epoxy composite with 5% filler loading were measured and the results indicated improvement in tensile and electrical properties. The diffraction patterns of X-ray diffraction (XRD) indicated nonlinear crystalline amorphous structure of the CB.     

Dispersion of multiwalled carbon nanotubes in a rubber matrix using an internal mixer: Effects on rheological and electrical properties

The dispersion of multiwalled carbon nanotubes (CNTs) in an ethylene propylene rubber matrix was investigated using an internal mixer. Poly(ethylene‐co‐polyvinyl acetate) (EVA) statistic copolymer was used as a dispersing agent. The effects of the concentration of the dispersing agent and the matrix viscosity on the quality of the dispersion of 1 wt % of CNTs were studied by using microscopy and rheology in the melt state. It was demonstrated that the dispersion is governed principally by the viscosity of the matrix. As expected, better dispersion was observed when the matrix exhibited a lower viscosity. The influence of the filler content on the rheological and electrical properties is presented. A Cross model with a yield stress is proposed to describe the rheological behavior of these materials, which exhibit a viscoelastic solid behavior from 1 wt % CNT content. Electrical measurement data indicate that the electrical percolation threshold was 2.9 wt %. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1597–1604, 2011     

Effect of silane coupling agent on the polymer‐filler interaction and mechanical properties of silica‐filled NR

The effects of filler loading and a new silane coupling agent 3‐octanoylthio‐1‐ propyltriethoxysilane (NXT silane) on the polymer‐filler interaction and mechanical properties of silica‐filled and carbon black‐filled natural rubber (NR) compounds were studied. Silica (high dispersion silica7000GR, VN2, and VN3) and carbon black (N330) were used as the fillers, and the loading range was from 0 to 50 phr. The loading of NXT silane was from 0 to 6 phr. Experimental results show that the maximum and minimum torques of silica and carbon black‐filled NR increase with increasing filler loading. With increasing filler loading, the scorch time and optimum cure time decrease for carbon black‐filled NR, but increase for silica‐filled NR. The minimum torque, scorch time, and optimum cure time decrease because of the presence of NXT silane. For the carbon black and silica‐filled NR, the tensile strength and elongation at break have maximum values, but the hardness, M300, M100, and tear strength keep increasing with filler loading. The mechanical properties of silica‐filled NR were improved in the presence of NXT silane. With increasing filler loading, the storage modulus of filled NR increases, but the loss factor decreases. Carbon black shows the strongest polymer‐filler interaction, followed by VN3, 7000GR, and VN2. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 573–584, 2005     

Alteration of matrix curing characteristics and its role in extension of hydrodynamic equation for predicting viscoelastic properties of nitrile rubber/silica nanocomposites

Neglecting the alteration of matrix curing characteristics in a filled rubber nanocomposite, as a result of possible interactions between the nano filler and curing agent ingredients, leads to inaccurate properties prediction using conventional hydrodynamic equations. In the current work, we present a new empirical extended version of hydrodynamic equation and examine its capability in predicting the viscoelastic properties of NBR/nanosilica system in which the negative influence of the filler on the curing process of the NBR matrix was confirmed through various analyses such as tensile test, rheometry, swelling experiments, and dynamic mechanical analysis. The results showed that the proposed empirical extended model is able to account the contribution of alteration of matrix curing characteristics in changing the composite properties below the filler percolation threshold. It was demonstrated that the extended model provides more accurate prediction of viscoelastic properties of silica‐filled cured NBR nanocomposites above glass transition temperature.     

Electrically conductive composites of polyethylene filled with polyamide particles coated with silver

New types of electrically conductive polymeric composites were prepared on a base of high-density polyethylene (HDPE) matrix filled with silver-coated polyamide (PA) particles. The electrical, mechanical and adhesive properties of those composites are reported in this paper. The percolation concentration of the filler within a matrix was found to be 4 vol.%. Composites filled with high filler content were highly electrically conductive; their electrical conductivity reached the value of 6.8 × 10² S cm⁻¹. Mechanical properties and rheology of these composites were discussed. The adhesive properties of the composites to metal sharply increased with an increase in the filler content.     

多壁碳纳米管/聚乙烯复合材料的制备及其导电行为

多壁碳纳米管/聚乙烯复合材料的制备及其导电行为;碳纳米管;高密度聚乙烯;渗流阈值;导电行为;V-PTC特性     

In situ polymerization of methyl methacrylate/multi-walled carbon nanotube composites using cationic stearyl methacrylate copolymers as dispersants

Novel water-soluble amphiphilic copolymers (poly[(stearyl methacrylate)-stat-([2-(methacryloyloxy)ethyl] trimethyl ammonium iodide)]) for dispersing multi-walled carbon nanotubes (MWCNTs) were used to carry out in situ methyl methacrylate (MMA) polymerization. The morphology of the poly(methyl methacrylate)/MWCNT composites and the dispersion of the MWCNTs were analyzed by transmission electron microscopy. The dispersion of multi-walled carbon nanotubes in the composites was excellent for cationic SMA (stearyl methacrylate) copolymers, even at high MWCNT loading (6.0 wt.%). The mechanical properties and electrical and thermal conductivities of the composites were also analyzed. Mechanical properties were improved by MWCNTs; the strain at break values remained stable up to 6.0 wt.% MWCNT loading. Both electrical and thermal conductivities were improved by the addition of MWCNTs.     

Highly enhanced electrical and mechanical properties of methyl methacrylate modified natural rubber filled with multiwalled carbon nanotubes

Developing conductive networks in a polymer matrix with a low percolation threshold and excellent mechanical properties is desired for soft electronics applications. In this work, natural rubber (NR) functionalized with poly(methyl methacrylate) (PMMA) was prepared for strong interfacial interactions with multiwalled carbon nanotubes (MWCNT), resulting in excellent performance of the natural rubber nanocomposites. The MWCNT and methyl methacrylate functional groups gave good filler dispersion, conductivity and tensile properties. The filler network in the matrix was studied with microscopy and from its non-linear viscoelasticity. The Maier-Göritze approach revealed that MWCNT network formation was favored in the NR functionalized with PMMA, with reduced electrical and mechanical percolation thresholds. The obvious improvement in physical performance of MWCNT/methyl methacrylate functionalized natural rubber nanocomposites was caused by interfacial interactions and reduced filler agglomeration in the NR matrix. The modification of NR with poly(methyl methacrylate) and MWCNT filler was demonstrated as an effective pathway to enhance the mechanical and electrical properties of natural rubber nanocomposites.     

Dispersion evaluation of microcrystalline cellulose/cellulose nanofibril-filled polypropylene composites using thermogravimetric analysis

Microcrystalline cellulose-filled polypropylene (PP) composites and cellulose nanofiber-filled composites were prepared by melt blending. The compounded material was used to evaluate dispersion of cellulose fillers in the polypropylene matrix. Thermogravimetric analysis (TG) and mechanical testing were conducted on composites blended multiple times and the results were compared with single batch melt blended composites. The residual mass, tensile strength, and coefficient of variance values were used to evaluate dispersion of the microcrystalline cellulose fillers in the PP matrix. The potential of using TG to evaluate cellulose nanofiber-filled thermoplastic polymers was also investigated and it was found that the value and variability of residual mass after TG measurements can be a criterion for describing filler dispersion. A probabilistic approach is presented to evaluate the residual mass and tensile strength distribution, and the correlation between those two properties. Both the multiple melt blending and single batch composites manufactured with increased blending times showed improved filler dispersion in terms of variation and reliability of mechanical properties. The relationship between cellulose nanofiber loading and residual mass was in good agreement with the rule of mixtures. In this article, the authors propose to use a novel method for dispersion evaluation of natural fillers in a polymer matrix using TG residual mass analysis. This method can be used along with other techniques such as scanning electron microscope (SEM), transmission electron microscope (TEM), and X-ray diffraction (XRD) for filler dispersion evaluation in thermoplastic composites.     

The use of surfactants for dispersing carbon nanotubes and graphene to make conductive nanocomposites

Applications of composites based on carbon nanotubes and graphene require their exfoliation and dispersion in a polymer matrix. One of the main approaches to disperse and exfoliate carbon nanotubes and graphene is based on the use of surfactants. Here we review the surfactants utilized for dispersing carbon nanotubes and graphene, the mechanisms of filler stabilization and the methods for composite preparation based on the use of surfactants to get conductive polymer composites with minimum nanofiller loading.     

Preparation and mechanical properties of water-dispersible hyperbranched polymer grafted carbon black/natural rubber composites by latex blending method

In order to improve the mechanical properties of rubber-matrix composites, carboxyl-terminated hyperbranched poly (2-hydroxypropane-1,2,3-tricarboxylic acid) grafted carbon black (CB-g-CTHBP) was prepared, and it could be stably dispersed in water for up to 90 days. CB-g-CTHBP dispersion and natural rubber latex were blended to obtain NR/CB-g-CTHBP, and the effect of CB-g-CTHBP content on the mechanical properties of composites was discussed. The results show that the dispersibility and wettability of CB-g-CTHBP to composites are significantly improved after grafting hyperbranched polymer onto the surface. Compared with the composite filled with NR/CB, when the amount of filler is 30 phr, tensile strength, tear strength, and shore A hardness of NR/CB-g-CTHBP increase by 54.78%, 55.13%, and 20.96%, respectively. Moreover, CB-g-CTHBP could disperse more evenly in the natural rubber-matrix, and the interaction between CB-g-CTHBP and rubber-matrix could further enhance in the composite.