Preparation and characterization of exfoliated graphite and its styrene butadiene rubber nanocomposites

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Abstract

Nanocomposites consisting of styrene butadiene rubber (SBR) reinforced with the modified-graphite and natural-graphite with concentrations of 5 wt% were fabricated. Processing techniques such as acid treatment, thermal shock, sonication were employed in the fabrication of modified-graphite.

The graphite platelets oxidized using sulfuric and nitric acids were analyzed by the Raman scattering, Fourier transformed infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The FT-IR results indicate the presence of acid groups in the treated samples, and Raman spectroscopy of acid-graphite platelets further corroborate the formation of surface defect due to the introduction of functional groups. However, the structure of XRD peaks did not change irrespective of processing techniques.

The SBR-based nanocomposites were characterized using the scanning electron microscopy (SEM), rheometer, Instron tensile machine, thermal and electrical analyser.

The results showed that nanocomposites onto acid-graphite platelets enhanced mechanical properties and fatigue properties of nanocomposites compared to those containing natural-graphite due to the increase in the interaction between the polymer and the modified-graphite. And the dynamic properties of nanocomposites had no influence according to the processing techniques. Also, thermal and electrical properties of nanocomposites using acid-graphite platelets were enhanced due to the broadened specific surface by the acid treatment.

Introduction

In recent years researches both in industry and in academia have focused their interest on polymeric nanocomposites, which represent a radical alternative to conventional filled polymers or polymer blends. In contrast to conventional systems, the reinforcement in the nanocomposites has at least one dimension in the nanometer range. This characteristic enables the nanoreinforcements whether inorganic, i.e., clay or organic, i.e., carbon nanotube, to enhance overall material performance by synergistically producing unique material properties.

The nanomaterials are more effective reinforcements than their conventional counterparts because smaller amount of nanomaterials causes a lager improvement of the matrix properties leading to lightweight composites with lower cost and easier processability. In addition, the stress transfer from the matrix to the reinforcement is more efficient in case of nanocomposites due to the increased surface area, assuming good adhesion at the interface. Also, the crack propagation length at the interface becomes longer, improving the strength and toughness.

A new nanoreinforcement, graphite-like nanoplatelets have recently attracted attention as a visible and inexpensive filler in composite materials [1] that can be used in many engineering applications, given the excellent in-plane mechanical, structural, thermal, and electrical properties of graphite. These excellent properties may be relevant at the nanoscale if graphite can be exfoliated into thin nanoplatelets, and even down to the single graphene sheet level [2].

Graphite nanoplatelets have often been made from expanded graphite, which in turn was produced from graphite intercalation compounds via rapid evaporation of the intercalant at elevated temperatures. For example, rapid thermal expansion of sulfuric and nitric acid-intercalated graphite, followed by a suitable treatment to produce platelets/nanoplatelets from the expanded material (ball milling or exposure to ultrasound) has been recently demonstrated [3], [4], [5], [6], [7]. Aylsworth [8], [9] developed and proposed exfoliated graphite as a reinforcement of polymers in 1910s. Lincoln and Claude [10] in 1980s proposed the dispersion of intercalated graphite in polymeric resins by conventional composite processing techniques. Since that time, research has been conducted on exfoliated graphite-reinforced polymers using graphite flakes of various dimensions and a wide range of polymers. Kalaitzidou et al. [11] have demonstrated the use of exfoliated graphite platelets to enhance the thermal and mechanical properties of polymeric resins. They concluded that composites made by in situ processing have better dispersion, prevention of agglomeration and stronger interaction between the reinforcement and the polymer. Debelak and Lafdi [12] dispersed exfoliated graphite flakes in an epoxy resin and studied the thermal and electrical properties of the composites. The increase in thermal conductivity was reported for the 20% graphite flakes composite compared to the pure resin.

With respect to the prior work reviewed above, in this study we chemically treat the graphite flakes and study the mechanical, thermal and electrical properties of the resultant composites.

The main goals of this work are to: (1) fabricate nanocomposites that contain natural-graphite, modified-graphite and carbon black in SBR matrix; (2) determine the mechanical properties of the nanocomposites, i.e., modulus, tensile strength, elongation and fatigue properties; (3) investigate the morphology of the modified-graphite and nanocomposites and (4) evaluate thermal and electrical properties according to the fillers.

Section snippets

Materials

The matrix material was a styrene butadiene rubber (SBR) from Kumho Petrochem Co. Ltd., Korea. The SBR1500 was consisted of 23% styrene and 77% butadiene. The reinforcing particles were pristine graphite supplied by Timcal. The properties of the as-received graphite platelets are summarized in Table 1. These graphite platelets consist of thin hexagonal plates or distorted clusters of flaky plates from SEM image.

The coupling agent is bis-(3-triethoxysilylpropyl)tetrasulfane that has

Materials characterization

Table 3 shows the Raman spectroscopy of natural-graphite and acid-graphite. The main features in the Raman spectroscopy of graphite are the so-called G- and D-bands, which lie at around 1560 and 1360 cm−1, respectively. G-band of the acid-graphite appeared almost the same as that of the natural-graphite, but the acid-graphite demonstrated an increased D-band. In other words, I(D)/I(G) ratio of acid-graphite is higher than that of natural-graphite. Since, the D-band is proportional to the defects

Conclusions

In the present work, we produced exfoliated graphite platelets through the rapid thermal expansion of sulfuric and nitric acid-intercalated graphite, followed by the ultrasonic treatment and also fabricated the nanocomposites that contain natural-graphite, modified-graphite and coupling agent in SBR matrix. It has been recently demonstrated the effects of those were investigated on the mechanical, fatigue, thermal and electrical properties of SBR composites with different modified fillers.

References (17)

  • G. Chen et al.

    Eur. Polym. J.

    (2003)
  • G. Chen et al.

    Polymer

    (2003)
  • G. Chen et al.

    Carbon

    (2004)
  • J.W. Aylsworth, US Patent 1,137,373,...
  • B. Debelak et al.

    Carbon

    (2007)
  • W. Zheng et al.

    Polymer

    (2002)
  • A. Yasmin et al.

    Compos. Sci. Technol.

    (2006)
  • K. Fukuda et al.

    J. Power Sources

    (2006)
There are more references available in the full text version of this article.

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