Hybrid fillers effects

So far, utilization of as-prepared clay-CNTs hybrid in polymer composites exhibits good properties, especially mechanical properties. However, the versatile structure of this hybrid synthesized by different processing conditions lead to different composites properties. So the effect of fabrication method and process parameters on final properties of polymer composites should be investigated more systematically. For example, the density and length (or diameter) of CNTs on clay platelets may affect the properties of hybrid. It is interesting to enhance the connection between clay and CNTs in order to obtain higher mechanical properties for the hybrid filler and composites. 

A method of incorporating simultaneously hybrid fillers of CB and MWNTs into a polymeric matrix has also been used to enhance the electrical conductivity of composites because the CB particles link the gaps between the unconnected MWNTs thus improving the formation of connected structures (51,52). In fact the synergistic effects arising between the two different fillers improve the dispersion of MWNTs in the polymer matrix. 

This PANl-MWCNT hybrid filler was solution blended with PS matrix (10-30 wt.% loading) resulting in absorption dominated total shielding effectiveness (SE.j.) of -45.7 dB (Figure 9.21a) in the 12.4-18.0 GHz range and at a sample thickness of 2.0 mm. The enhanced SE.j. was ascribed to optimization of electrical conductivity, skin depth, complex permittivity... 

A synergistic effect was also found between clay and CB N330 from Cabot, in NR based nanocomposites prepared by emulsion compounding.It was observed that both fillers were dispersed at nanoscale and randomly in the NR matrix the space between the clay layers was filled with CB particles. The mechanical properties of the nanocomposites, such as moduli at 100% and 300% elongation, tensile strength and tear strength were much improved, at the same total filler level, by the hybrid filler system, with respect to composites containing only one filler. 

Jong et prepared NR composites reinforced with hybrid filler consisting of defatted soy flour (DSF) and CB. Aqueous dispersions of DSF and CB were first mixed, and then blended with NR latex and sulfur dispersion, respectively. The homogenous composite mixtures were quickly freeze-dried and compression moulded to offer the NR composites. They found that the NR composites reinforced with 40% of hybrid filler (the ratio of DSF to CB was 1 1) exhibited a 90-fold improvement in the rubber plateau modulus compared with unfilled NR, showing a significant reinforcement effect by the hybrid filler. 

Another promising approach to preparation of novel NR composites and nanocomposites with excellent properties is to adopt hybrid fillers because each reinforcing agent can retain its inherent advantages, which imparts a synergistic effect between hybrid fillers to reinforce NR nanocomposites. 

Figure 8.21 Filler-filler network (Payne effect) in hybrid filler filled NR composites.

Effects of Hybrid Fillers on Mechanical Properties of Natural Rubber Composites... 

Effect of Hybrid Fillers on the Non-Linear Viscoelasticity of Rubber Composites and Nanocomposites... 

Polymer/mbber nanocomposites exhibit enhanced mechanical, thermal stability, toughness, stiffness, and gas-barrier properties compared to those of conventional composites at same filler volume fraction [11-15]. The interaction between the filler and polymer matrix of nanocomposites at the nanometer scale enables the formation of molecular bridges in the polymer matrix. This is the basis for the enhanced mechanical properties of nanocomposite as compared to conventional microcomposites [16, 17]. Nanocomposites containing hybrid fillers add a new dimension to the above enhanced properties. These composites show more advantages to composites containing single filler as the property of the hybrid filler composite depends upon the combined effect of individual filler. The nonlinear viscoelastic behavior of nanocomposites can be influenced differently by hybrid fillers than single filler. 

This chapter focuses on the non-linear viscoelastic behavior of rubber composites and nanocomposites. Here, we have discussed about the effect of individual fillers (mineral fillers, nanotubes, carbon nanofillers, fibrous nanofiUers, biofillers, special structured fillers viz. nanorods, nanowires, nanoflowers etc.) on the linear/ nonlinear viscoelastic behavior of rubber composites. Moreover, as this chapter is more concerned on the non-linear viscoelastic behavior, we have also discussed the effect of hybrid fillers on the nonUnear viscoelastic behavior of rubber composites in more detail. 

Yu L, Park JS, Lim Y-S, Lee CS, Shin K, Moon HJ, Yang C-M, Lee YS, Han JH (2013) Carbon hybrid fillers composed of carbon nanotubes directly grown on graphene nanoplatelets for effective thermal conductivity in epoxy composites. Nanotechnology 24 155604... 

Park DH, Lee YK, Park SS, Lee CS, Kim SH, Kim WN (2013) Effects of hybrid fillers on the electrical conductivity and EMI shielding efficiency of polypropylene/conductive filler composites. Macromol Res 21(8) 905... 

Yoo TW, Lee YK, Lim SJ, Yoon HG, Kim WN (2014) Effects of hybrid fillers on the electromagnetic interference shielding effectiveness of polyamide 6/conductive filler composites. J Mater Sci 49 1701... 

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