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This paper reports a study on the effect of silica nanoparticles on the adhesion strength of steel-glass/epoxy composite joints bonded with two-part structural acrylic adhesives. The introduction of nano-silica in the two-part acrylic adhesive led to a remarkable enhancement in the shear and tensile strength of the composite joints. The shear and tensile strengths of the adhesive joints increased with addition of the filler content up to 1.5 wt%, after which decreased with addition of more filler content. Also, addition of nanoparticles caused a reduction in the peel strength of the joints. Differential scanning calorimeter analysis revealed that T g values of the adhesives rose with increasing the nanofiller content. The equilibrium water contact angle was decreased for adhesives containing nanoparticles. Scanning electron microscope micrographs revealed that addition of nanoparticles altered the fracture morphology from smooth to rough fracture surfaces.

Thin flexible double‐layer microwave absorbers have been fabricated based on polypyrrole (PP)/natural rubber (NR) nanocomposites and their reflection loss characteristics were studied in the range of 8–18 GHz. The PP‐NR matrix was prepared from PP and NR in the ratio of 15:85. The polymers used in this work not only serve as the matrix but also improve the microwave absorption properties. The first layer or impedance matching layer which is comprised of graphite, Fe3O4, and TiO2 nanoparticles in PP‐NR transmits the electromagnetic (EM) wave without reflection. The second layer which is made up of PP‐NR filled with Fe3O4 disperses the EM wave energy. The design of a double‐layer nanocomposite is a method to match the wave impedance, enhance wave absorption ability, and broaden the absorption frequencies. In order to achieve high absorption properties, the EM parameters such as permittivity, permeability, and thickness were controlled precisely according to quarter‐wave plate. The morphology, absorption properties, scattering parameters, thermal and wetting characteristics of double‐layer nanocomposites were investigated. The minimum reflection loss (RL) was −32 dB at 12.1 GHz and the absorbing bandwidth in which the RL < −10 dB was 9 GHz for optimum specimen with 2 mm thickness. For this specimen, the contact angle was equal to 118.7° with water as the liquid. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46565.

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