Nanocomposites from styrene–butadiene rubber (SBR) and multiwall carbon nanotubes (MWCNT) part 2: Mechanical properties

doi:10.1016/j.polymer.2014.11.006

Polymer

Volume 56, 15 January 2015, Pages 443-451

https://doi.org/10.1016/j.polymer.2014.11.006 Get rights and content

Highlights

•
Uncoiling of curved discreet MWCNT resulted in higher values of elongation and tensile stresses at break.
•
Enhanced tear energy for MWCNT filled SBR-CB composites is due to crack bridging mechanism.
•
Good interfacial adhesion between MWCNT and SBR caused the reduction in swelling ratios in toluene.

Abstract

Due to their high aspect ratio, strength, and modulus, multiwall carbon nanotubes (MWCNT) have attracted interest as a reinforcing filler in the automotive tire industry. In part 1 of this study, we demonstrated that styrene–butadiene rubber (SBR) composites containing up to 15 wt. % of well-dispersed, discreet MWCNTs can be prepared using MWCNTs with a specific surface modification and controlled aspect ratios. The melt rheology of the composites with discreet MWCNT was best described in terms of an effective aspect ratio and by considering the discrete MWCNT to be flexible rather than rigid rods. In this work, the effect of tensile strains, up to values of 6, for cured SBR composites containing discreet MWCNT concentrations up to 12% by weight were investigated. The deformation behavior indicates good adhesion between these MWCNT and the SBR. Mooney–Rivlin plots derived from the composite tensile stress–strain data displayed a dramatic change in mechanical behavior as the MWCNT loading exceeded about 5 wt. % attributed to a combined reinforcing effect of tubes on SBR plus overlap of curved or coiled MWCNT. Beyond tensile strains of about 1.7, strain hardening increases dramatically at MWCNT loading greater than 5 wt. % that is attributed straightening of the initially curved nanotubes such that they behave as rigid rods or fibers. Mechanical hysteresis and swelling in toluene on cured composites samples revealed that MWCNTs are in fact well bonded to the SBR. Studies with SBR and a combination of carbon black and discreet MWCNT demonstrate dramatically improved resistance to fracture by tearing.

Graphical abstract

Introduction

Styrene–butadiene rubber, SBR, is widely used as one of the components of the elastomeric matrix for automotive tires [1], [2], as well as for wire and cable applications, and sporting goods. For enhanced performance of tires, SBR composites should possess good mechanical properties including improved wear and tear resistance. SBR is most often blended with other rubbers such as natural rubber and poly(cis-butadiene) for specific applications. Various combinations of conventional fillers with low aspect ratios such as carbon black, silica, and clays, etc., have been employed to enhance mechanical [1], [3], [4], [5], [6], [7], [8], barrier [9], [10], [11], [12], [13] and tear properties. Typically, such composites contain high loadings of these conventional fillers up to 60 parts per hundred of rubber, phr [14]. It is also well recognized that polymer-filler composites with such loadings invariably involve some agglomeration of particles due to poor interaction between the polymer and the particle surface plus strong interparticle interactions [15]. These agglomerates can cause deterioration of properties such as wear resistance.

When a tire tread undergoes cyclic loading and strains in actual use, nano-sized voids form at stress concentration locations at and between filler–elastomer interfaces. Under repetitive loading, these voids can coalesce and grow in size to form micron-sized cracks; this eventually leads to failure of the tire. A number of crack propagation mechanisms have been proposed in the literature for elastomers [16], [17], [18], [19], [20] demonstrating how cracks form in elastomer composites loaded with conventional fillers such as carbon black (CB) and/or silica. Multiple efforts have been made to prevent the propagation of nano-sized voids into micron-sized cracks and to further enhance the mechanical properties of the composite by adding a small amount of multiwall carbon nanotubes (MWCNT) [21], [22], [23]. The MWCNTs are anticipated to act as crack bridging elements due to their high aspect ratios and their inherent high tensile modulus (1 TPa) and strength (50–500 GPa) [24], [25], [26], [27]. The basic requirements for the MWCNT to act as crack initiation and growth inhibitors include being well-dispersed and having good adhesion or being bonded to the matrix. However, since rubbers such as SBR may be deformed to high strains, the fillers have to accommodate these high strains without causing premature failure within the rubber phase.

In previous studies, even though MWCNT-filled elastomers exhibit some improvement in tensile properties, they generally do not reach their expected performance based on the properties of the tubes themselves. This may be attributed primarily to lack of discrete MWCNT, poor MWCNT dispersion and weak tube-to-matrix surface adhesion [28].

Part 1 of this series reported a process for making masterbatches containing up to 15 wt. % of discreet, well-dispersed MWCNTs in a SBR matrix using an emulsion coagulation technique [29]. The concentrated masterbatches could be diluted with SBR to give lower MWCNT loadings while preserving excellent tube dispersion. A key to this technology is proper surface functionality and controlling tube aspect ratio at an optimum level to achieve rheological properties that permit processing while preserving good mechanical properties. In particular, the carbon nanotubes were observed to be highly curved or coiled and as such, an effective aspect ratio determined from the overall tube contour length to end–end distance was found to be a more relevant parameter to relate to the composite rheology under various strain rates. The changes in effective aspect ratio with dilution indicates that the tubes are best considered as being flexible rather than rigid rods.

In this study, composites made by curing nanocomposites formed by dilution of such a masterbatch will be used to investigate the tensile and tear properties. Mechanical hysteresis experiments on these cured composites are performed to understand the interactions between MWCNT and SBR. These results are further supported by swelling studies in toluene. These studies form a basis for future work on MWCNT composites based on blends of rubber of the type used in commercial tires; further papers will discuss the mixing rules of various masterbatches, rheology, and various mechanical properties.

Section snippets

Materials

The multiwall carbon nanotube/SBR composites studied here were prepared from a MWCNT/SBR masterbatch prepared by a coagulation process followed by melt mixing in a high shear twin-screw extruder. The masterbatch was then diluted to various carbon nanotube concentrations with additional SBR plus curing additives by melt compounding in a Haake batch mixer. These mixed masterbatches were pressed into sheets and cured as described previously [29]. The pure MWCNTs and CB had specific surface areas

Results and discussion

Tensile stress–strain curves for cured SBR composites containing from 1 to 12.3 wt. % MWCNT are shown in Fig. 2a and compared with cured SBR. As expected, the stress levels of the composites increase with MWCNT loading at all strains. From a loading of 4–5 wt. % MWCNT and above, the stress vs. strain curves become more linear compared with those at lower MWCNT concentrations. To further understand these tensile results, the data are recast in the form of a reduced stress, σ_r, versus reciprocal

Conclusions

Tensile stress–strain measurements were performed on cured SBR samples containing various loadings of MWCNT. The elongation at break remained at the level of SBR (∼460%) until about 7.5 wt. % MWCNT and then decreased slightly while the stress at break increased by 210% up to 7.5 wt. % MWCNT reflecting the reinforcing effect of MWCNT and its interactions with SBR. Mooney–Rivlin plots derived from the tensile stress–strain curves show that the curves shift towards higher reduced stress values

Acknowledgments

The authors would like to thank Dr. M.F. Finlayson for preparing the initial masterbatch and Macon Leighton for helping with the tear testing. The authors also like to thank Molecular Rebar Design, LLC for funding this project and instrumentation support.

References (57)

B.B. Boonstra
Polymer
(1979)
G. Heinrich et al.
Curr Opin Solid State Mater Sci
(2002)
M. Alexandre et al.
Mater Sci Eng R-Rep
(2000)
A. Allaoui et al.
Compos Sci Technol
(2002)
Y.-L. Lu et al.
Compos Sci Technol
(2007)
R. Stephen et al.
Polymer
(2006)
Z.F. Wang et al.
Polymer
(2005)
M. Bhattacharya et al.
Polymer
(2011)
G. Previati et al.
Int J Fatigue
(2012)
A. Das et al.
Polymer
(2008)

S. Bhattacharyya et al.

Carbon

(2008)

N.J.S. Sohi et al.

Carbon

(2011)

X.-L. Xie et al.

Mater Sci Eng R Rep

(2005)

R. Byron Pipes et al.

Compos Sci Technol

(2003)

S.K. Peddini et al.

Polymer

(2014)

F. Li et al.

Polymer

(2013)

B. Meissner et al.

Polymer

(2000)

B. Meissner

Polymer

(2000)

K. Sakulkaew et al.

Polym Test

(2011)

H. Ambacher et al.

Kautsch Gummi Kunstst

(1991)

J.S. Bergstrom et al.

Rubber Chem Technol

(1999)

M. Biswas et al.

Recent progress in synthesis and evaluation of polymer-montmorillonite nanocomposites

T. Ramanathan et al.

J Polym Sci Part B-Polym Phys

(2005)

L.D. Perez et al.

Polym Eng Sci

(2009)

L. Bokobza et al.

J Appl Polym Sci

(2002)

C.R. Herd et al.

Rubber Chem Technol

(1991)

H. Aglan et al.

Int J Fract

(1990)

R.S. Rivlin et al.

J Polym Sci

(1953)

Cited by (85)

Impact of fiber coating with hydrophobic nanoparticles polymer on the physicomechanical properties of Pisum sativum L. fibers/ styrene butadiene rubber ecofriendly composites
2024, Industrial Crops and Products
Hydrophobic nanoparticle copolymers of vinyl acetate and different ratios of veova10 were used to coat Pisum sativum L. fibers (PSF). The impact of coating process on the reinforcement efficiency of PSF of styrene butadiene rubber (SBR) was investigated. The morphology study, indicated that, the coating with hydrophobic nanoparticle copolymers improved the interfacial adhesion between the PSF and SBR. The tensile strength (TS) of the composites containing coated fibers recorded the highest tensile properties, the lowest Mullins effect and the highest resistance to water absorption. The coating process improved the TS of PSF/SBR composite up to 35.3% after incorporation of 10 phr of coated PSF. The PSF/SBR composite containing 20 phr of coated fibers recorded water uptake of 14.18% compared to 23.24% for composites containing uncoated fibers. The PSF/SBR composites exhibited more biodegradation rate than that of neat SBR. The results indicated that the PSF coated with the prepared hydrophobic polymers had a beneficial impact on the physicomechanical properties of the PSF/SBR composites.
Green synthesized Al-metal complex to reduce the crystalline phase and improve the optical properties of CS based polymer blends
2022, Optical Materials
Citation Excerpt :
The other cause is the stronger light adsorption between functional groups of the host polymer and metal complex particles, leading to a lowering of the functional groups vibrational intensity [35,38]. The previous work on the Al3+-polyphenol complex was conducted by Aziz et al. [5] and other studies on metal complexation have confirmed that caffeine and polyphenols possess strong affinity for metal ions [30,39]. Table 1 presents Catechins as the major component of polyphenols in black tea.
In the present study, a green coordination chemistry technique is used for the preparation of Aluminum complexes (Al³⁺-polyphenol complex) by using black tea extract solution. Chitosan: Poly(2-ethyl-2-oxazoline) (CS: POZ) composite samples loaded with Al³⁺-complex was arranged by solution casting technique. Various techniques were used to characterize the films, such as UV–Visible spectroscopy, fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD). The shifting of the peaks and their reduction in intensity in both XRD and FTIR confirmed the amorphous development with the loading of the Al³⁺-complex and the production of strong interaction between functional groups of the CS: POZ with the Al³⁺-complex, respectively. The insertion of the Al³⁺-complex into the host polymer matrix resulted in the creation of a polymer composite with controlled optical properties and improved optical parameters, including dielectric constant ( $ε_{r})$ , dielectric loss ( $ε_{i}$ ) and refractive index (n). The complex dielectric constant's real and imaginary components as a function of photon wavelength were explored to derive various high-frequency characteristics. This includes extracting dielectric constant at short wavelength $(ε_{\infty})$ , optical resistivity ( $ρ_{o p t}$ ), localized charge density values (N/m*), plasma angular frequency ( $ω_{p}$ ), optical mobility ( $μ_{o p t}$ ), and relaxation time ( $τ$ ) of electrons, in which all these optical parameters are important for choosing suitable materials for optoelectronic applications. In accordance with (45 ml of Al³⁺-complex insertion), both $ω_{p} a n d$ N/m* magnitudes are enlarged up to 10-times, while the optical band gap is remarkably dropped (4.8–1.65 eV), which is calculated using Tauc's relation, and the electronic transition mode was identified by using optical dielectric loss ( $ε_{i}$ ). Moreover, the Wemple–DiDomenico single oscillator model was applied to study the dispersion behavior of their refractive index and estimate the oscillator dispersion energy ( $E_{d}$ ) and average oscillator energy ( $E_{o}$ ) and parameters. The polymer composite with absorption performance in the visible region and other superior optical properties is fundamental for photo cells and commercialization in optoelectronic devices.
Antimicrobial studies in rubber nanocomposites—A mini review
2022, Industrial Crops and Products
Infectious diseases are considered as a significant threat to human health as well as environment. Due to the increasing microbial diseases, researchers are trying to find out new materials with superior antimicrobial properties. Insertion of various nanofillers into rubber matrices will result in the production of advanced rubber nanocomposites with improved mechanical, electrical, thermal and barrier properties. However, improvement in antimicrobial properties of rubber nanocomposites is still remaining as an unexplored area. But the existing studies show that, the addition of antimicrobial nanofillers can introduce antimicrobial properties into the final rubber nanocomposites and thus can be used in various biomedical applications. Thus the present review tries to bring together all the available antimicrobial works in the area of rubber nanocompositses.
Impact of gamma radiation and multi-walled carbon nanotubes on the mechanical and acoustical properties of reinforced sisal fiber/polyester resin composites
2021, Radiation Physics and Chemistry
Citation Excerpt :
The elongation at break decreased dramatically with higher MWCNT loadings. The MWCNT has high aspect ratio which permits a high degree of load transfer between the polyester matrix and MWCNT that prevents failure at low stresses (Peddini et al., 2015). Also, the crosslinking induced by gamma radiation restricts the segmental motion and consequently decrease the elongation at break (Abdel-Hakim et al., 2019).
In this work, the effect of exposure to 5 kGy of Gamma radiation and the addition of Multi-walled carbon nanotubes (MWCNT) in different concentration 0, 0.2, 0.4 and 0.6 wt% to sisal fiber/unsaturated polyester resin (SF-UP) composites (40/60) on the mechanical and acoustical properties was investigated. An enhancement in the mechanical properties was achieved by addition MWCNT up to 0.4%, and then decreased at 0.6%. Also, irradiation of the composite manifested an enhancement in the mechanical properties more than unirradiated ones. The tensile strength and flexural strength of irradiated SF-UP composite which contains 0.4% MWCNT were higher than unirradiated SF-UP composite which contains 0% MWCNT by 73.2 and 91.9%, respectively. The addition of MWCNT and exposure to 5 kGy of gamma radiation increased both the storage modulus and the Tg while the damping factor (tan δ) decreased. Increasing the MWCNT % enhanced the sound absorption at the higher frequencies (0.6% MWCNT (unirradiated)∼0.9 within 5000–6300 Hz), while the irradiation shifted the highest absorption toward lower frequencies (0.6% MWCNT (irradiated)∼0.63 within 2500–3150 Hz). The produced composite displayed appreciable mechanical and acoustical properties which makes it as a new partner for many advanced industrial applications.
Prediction of mechanical properties of graphite nanoflake/polydimethylsiloxane nanocomposites as affected by processing method
2021, Composites Part B: Engineering
Citation Excerpt :
In addition, almost no model has estimated the mechanical properties in consideration of interior voids, which inevitably come about when the liquid-state solution of filler-reinforced nanocomposites is formed to shape. Most of the previous studies focused on quantitatively characterizing the dependence of mechanical properties on the rudimentary factors such as the intrinsic properties of individual constitutes, the size, shape (or aspect ratio) [20,75], and content of a filler [38,75,76], the interface adhesion between filler and matrix [77,78], etc. Changes in the dispersion and orientation of filler induced by manufacturing processes were also addressed as dominant factors for determining the mechanical properties.
Porosity is suppressible but unavoidable in manufacturing nanocomposites, therefore affecting their mechanical properties like intrinsic properties and other filler-related factors. Despite all the efforts, it is still regarded as challenging to develop theoretical models for mechanical properties of filler-reinforced nanocomposites which consider void defects created during manufacturing process. Here, graphite nanoflake/polydimethylsiloxane (GnF/PDMS) nanocomposites for paint-on applications are manufactured with different processing methods (i.e., solvent casting, hand lay-up, and spray lay-up) to address imperfections involved in each process and their implication to mechanical properties. The manufacturing processes were found to have almost no alternation on filler-related features (i.e., size, orientation, and distribution) except porosity. The evolution of a porosity is best modeled with the logistic function. We establish a set of prediction models for elastic modulus, fracture strength, and elongation at break by combining the previous models (i.e., Tsai-Hahn, Piggott-Leidner, and Landel-Nielsen models) with the logistic function on porosity. The proposed models are in good agreement with the experimental data on GnF/PDMS nanocomposites. The effect of process method on surface morphology is also discussed.
Temperature impact on the mechanical and fatigue behavior of a non-crystallizing rubber
2021, International Journal of Fatigue
Temperature is one of the main parameters affecting the mechanical behavior of rubbers. The impact of this parameter is particularly important in the case of cyclic loads. In this study the mechanical and fatigue behavior of a carbon filled acrylonitrile butadiene rubber (NBR) was investigated. Tensile tests revealed a general decrease of the ultimate properties with temperature. Moreover, the maximum chain extensibility, evaluated through Mooney-Rivlin plots, showed a similar trend and a minimum at intermediate temperature. The dynamic properties of the material were investigated through DMA measurements. Temperature sweep revealed an Arrhenius dependence of the dynamic moduli for temperatures above T_g + 30 °C. Master curves of the dynamic properties were generated through the application of the time-temperature superposition principle, by shifting horizontally the isothermal frequency sweeps. The fatigue behavior at different temperature was assessed through the crack growth approach and a lower crack growth resistance was found at higher temperatures. Finally, a new procedure for building fatigue master curves has been investigated by exploiting the temperature dependence of the loss modulus.

View all citing articles on Scopus

View full text

Nanocomposites from styrene–butadiene rubber (SBR) and multiwall carbon nanotubes (MWCNT) part 2: Mechanical properties

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Materials

Results and discussion

Conclusions

Acknowledgments

Polymer

Curr Opin Solid State Mater Sci

Mater Sci Eng R-Rep

Compos Sci Technol

Compos Sci Technol

Polymer

Polymer

Polymer

Int J Fatigue

Polymer

Carbon

Carbon

Mater Sci Eng R Rep

Compos Sci Technol

Polymer

Polymer

Polymer

Polymer

Polym Test

Kautsch Gummi Kunstst

Rubber Chem Technol

Recent progress in synthesis and evaluation of polymer-montmorillonite nanocomposites

J Polym Sci Part B-Polym Phys

Polym Eng Sci

J Appl Polym Sci

Rubber Chem Technol

Int J Fract

J Polym Sci