SWNT-filled polystyrene (SWNT-PS) and styrene−isoprene (SWNT-SI) composites prepared by miniemulsion polymerization showed distinctive physical features such as uniform black coloration, high solubility in toluene as well as in tetrahydrofuran (THF), and semiconductor to ohmic electrical behavior. Raman spectra for both hybrid materials suggested a reduced vibrational freedom of the polymer chains as a consequence of the nanotube incorporation. An adsorbed polymer layer on the nanotube bundles contributes to a better dispersion of the inorganic nanoreinforcement.

The effects of flow rate and post-fill cure pressure, i.e., packing pressure, on the mechanical properties of resin transfer molded disks are experimentally investigated. An experimental molding setup is constructed to fabricate fiber-reinforced, center-gated, disk-shaped composite parts. Disks are molded at different flow rates and packing pressures in order to observe the effects of these parameters on the mechanical properties and void content of the final parts. Specimens are cut from three different locations in the molded disks for testing. Specimens from the first two locations are tensile tested to obtain strength and stiffness properties, and the third location is used for microscopic analysis to determine void content and void properties. Increased injection rate is found to reduce both the strength and stiffness of the molded parts due to more voids induced by the faster moving fluid front. Packing pressure is also found to have a significant effect on specimen properties. At higher packing pressures fewer voids and improved strength and stiffness are observed. Mechanical properties are correlated with total void fraction for disks molded at different packing pressures. Exponential decrease in both tensile strength and elastic modulus is observed with increasing void fraction. Doubling the void volume fraction from 0.35 to 0.72% results in a 15% decrease in strength and a 14% decrease in stiffness. The results demonstrate that selection of suitable injection rate and addition of packing pressure to resin transfer molding (RTM) process can improve mechanical properties of molded parts considerably.

Advancing contact angles in the order of 70°to 80°were measured for Newtonian fluids at relatively high capillary numbers using a system of parallel glass plates. The transient height attained by the fluids between the plates was fitted to an averaged-flow Navier-Stokes model in order to indirectly estimate the value of the dynamic advancing angle. Subsequently, using a highly nonlinear approximation for the contact angle, it was possible to describe the entire relaxation phenomena during the capillary rise at low meniscus rates (e.g., high viscosity fluids), as well as at front velocities on the order of a hundred millimeters per second (e.g., low viscosity fluids). Contact angles obtained by the parallel plates method agree well with experimental observations and phenomenological correlations put forward in recent literature, but cannot be explained in terms of the proportionalities between dynamic angle and velocity predicted by the classical hydrodynamic and molecular theories in the nonwetting case.

Interfacial properties of glass fibers coated by admicellar polymerization with a styrene−isoprene copolymer thin film have been investigated. Advancing and receding contact angles on single glass fibers as small as 6.2 μm in diameter were measured at slow meniscus velocities (2.0 μm/s) by using the Wilhelmy method with probe liquids of various hydrophobic/hydrophilic characteristics. Distinctly different contact angles were obtained from the dynamic wetting of fibers with different surface treatments. In water, the average advancing contact angle for admicellar-modified fibers was high (θadv ≈ 65−75°), suggesting an increased hydrophobicity as compared to that of the fully wettable desized fibers. Furthermore, it was found that both fibers with silane coupling agents and admicellar-coated fibers are chemically heterogeneous on their surfaces. Contact line pinning behavior induced by regions of different surface energy, as well as high hysteresis values, indicates that the ultrathin styrene−isoprene film is not uniform throughout the glass on a macroscopic length scale. However, when assessed with an epoxy resin (e.g. EPON 815C), the admicellar polymerization treatment produced fibers with statistically identical wetting characteristics to those of fibers containing a proprietary sizing. Good adhesional wetting of the elastomer-modified fibers by an epoxy resin may be indicative of an adequate interaction between fiber and matrix in large-scale composite fabrication.

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