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The effect of dispersants on particle dispersion and flexural properties of SiC/vinyl ester nanocomposites was studied by factorial and response surface designs. The results show that the coupling agent 'gamma-methacryloxy propyl trimethoxy silane (MPS)' has no adverse side effect on the flexural properties as illustrated by the good correlation between maximizing the flexural strength and minimizing the agglomerates. However, the dispersant 'BYK-W 966' has a slight adverse side effect on the flexural properties although it improves dispersion at higher dosage. With an optimal dosage of MPS and W966, a small amount of SiC in 0.5 wt% results in 8% increase in strength and 14% increase in modulus. The flushing operation using the dispersant '1-octanol/decane' achieves an excellent SiC dispersion but it does not result in improved flexural properties. This confirmed that a better state of nanoparticle dispersion does not necessarily lead to improved flexural properties. A good dispersion coupling with a strong filler/matrix interfacial bonding is the key to obtain enhanced flexural properties.

The feasibility of improving polymer composites was investigated using 30 nm SiC nanoparticles in a vinyl ester resin. Even when the particle loading was less than 4% by weight, the viscosity of the nanoparticle suspension was found to increase much higher than that of microparticle suspension. This phenomenon may be the result of association between nanoparticles and polymer molecules, effectively making the nanoparticles larger. The resulting reduction in the mobility of polymer molecules also led to delayed curing. Ultrasonic mixing did not fully disperse the particles. As a result, the composite strength did not improve although the modulus increased. The use of a dispersant, methacryloxy propyl trimethoxy silane (MPS), improved the dispersion quality and hence the composite strength. The paper discusses the issues involved with processing, characterization and properties of SiC/vinyl ester nanocomposites. Methods of improving the nanocomposite quality are proposed in the paper as well.

Flexible high-loading nanoparticle-reinforced polyurethane magnetic nanocomposites fabricated by the surface-initiated polymerization (SIP) method are reported. Extensive field emission scanning electron microscopic (SEM) and atomic force microscopic (AFM) observations revealed a uniform particle distribution within the polymer matrix. X-ray photoelectron spectrometry (XPS) and differential thermal analysis (DTA) revealed a strong chemical bonding between the nanoparticles and the polymer matrix. The elongation of the SIP nanocomposite under tensile test was about four times greater than that of the composite fabricated by a conventional direct mixing fabrication method. The nanocomposite shows particle-loading-dependent magnetic properties, with an increase of coercive force after the magnetic nanoparticles were embedded into the polymer matrix, arising from the increased interparticle distance and the introduced polymer?particle interactions.