Wear behavior of epoxy matrix composites filled with uniform sized sub-micron spherical silica particles
Introduction
Inorganic particulate filled epoxy matrix composites have been extensively studied during the last two decades due to their increasing applications in coatings, electronic packaging and dental restoratives [1], [2]. The particles in these composites are generally of micrometer size. Use of nanoparticles as fillers in epoxy matrix composites is nowadays attracting a great deal of attention from materials scientists, technologists and industrialists [3], [4], [5]. These new nanocomposite systems could have broader application potentials with their unique optical, electrical and magnetic properties. The success of their technical applications depends to a large extent on a good understanding of both the nature of the nanocomposites and the relationship between structures, properties and processing. Obviously, their mechanical response is essential to the understanding. In particular, an understanding of the wear properties of the composites is important in some applications.
The understanding of the wear behavior of inorganic nanoparticle filled epoxy matrix composites is still very limited [5], [6]. The wear resistance of the nanocomposites might be decreased or increased depending on the type of particles, particle size and size distribution, interfacial actions between particle and matrix resin, particle content, and state of dispersion of the particles in the composites, as well as wear test conditions, i.e. wear mode (pin-on-disc or another one), counterface, sliding velocity, sliding distance, applied load, test temperature and humidity.
In this study, we focused on the effect of particle size on the wear behavior of nanocomposites at low levels of filler content. Two distinct sizes of uniform sized sub-micron spherical silica were used as model fillers. Wear tests using pin-on-disc mode were carried out and the wear mechanisms were studied by scanning electron microscope (SEM) observations. The wear mechanisms were discussed based on the obtained results. This work will contribute to the better understanding of the nanoparticle filled epoxy matrix composites, which is fundamental in their applications.
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Materials
Uniform sized spherical silica particles were prepared in our laboratory via the sol–gel process [7] using a modified Stobe method [8]. Two distinct sizes of silica particles were prepared and used in this work. The diameter of the particles was 120±8 and 510±30 nm, respectively (Fig. 1). The silica particles were heated at 600 °C for 1 h in order to remove possible organic residues on the particle surface prior to use. Epoxy of bisphenol A type (Dow Chemicals, D.E.R 324) and isophonyl diamine
Wear rate
The wear rate, K, as defined by Eq. (1) for the composites was plotted against particle content in Fig. 2. The adding of uniform sized spherical silica particles with diameter of 120 or 510 nm reduced the wear rate of the unfilled epoxy significantly. The reduction of the wear rate could be up to 2–10 times. This was true for the particle content range 0.5–4.0 wt.%. A particle content of 2.0 wt.% seemed to be most effective.
The silica fillers with smaller size (i.e. 120 nm) seemed to be more
Discussion
The wear mechanisms of epoxy and particulate filled epoxy matrix composites under the pin-on-disc condition had been previously discussed by Durand et al. [10]. The mechanisms included formation of cracks, development from cracks to waves and production of debris. The presently studied epoxy matrix should undergo similar wear mechanisms, although the thickness of the material waves of the epoxy in this work was around 2–5 μm, which was much smaller than the material wave thickness of 15 μm
Conclusions
The effects of uniform sized sub-micron spherical silica particles on the wear behavior of epoxy matrix composites were studied. The particle diameters used were 120 and 510 nm, respectively. The wear rate of the composites was reduced dramatically by adding a small amount (i.e. 0.5–4.0 wt.%) of either type of silica filler (120 and 510 nm in diameter, respectively). The smaller sized particles seemed to be more effective in improving the wear resistance.
Acknowledgements
The authors would like to thank Dr. Patrick Wong (Department of Manufacturing Engineering and Engineering Management, City University of Hong Kong) for providing the wear testing facilities. The work described in this paper was supported by a grant from the Research Grants Council of the Hong Kong Special Administrative Region, China (RGC Ref. No. 9040719). XSX was supported by a Postgraduate Studentship provided by the City University of Hong Kong.
References (11)
- et al.
Integral passives for next generation of electronic packaging: application of epoxy/ceramic nanocomposites as integral capacitors
Microelectron. J.
(2001) - et al.
Effect of particle size on the optically transparent nano meter-order glass particle-dispersed epoxy matrix composites
Comp. Sci. Technol.
(2002) - et al.
Tribological behaviour of DLC coatings compared to different materials used in hip joint prostheses
Wear
(2001) - et al.
Role of reinforcing ceramic particles in the wear behaviour of polymer-based model composites
Wear
(1995) - C.A. May (Ed.), Epoxy Resins—Chemistry and Technology, 2nd ed., Marcel Dekker, New York,...