Local heating and curing of carbon nanocomposite adhesives using radio frequencies

Abstract

Abstract Carbon nanoparticles are known to produce a strong, rapid heating response in the presence of a radio-frequency (RF) electromagnetic field. Here we show that this property can be used to selectively cure nanocomposite thermoset adhesives in plastic bonding applications without deforming the surrounding plastic components. A non-contact RF applicator was used to generate an electric field through a carbon-black-loaded adhesive, which then volumetrically heats and cures the adhesive that bonds two plastic substrates. Because this heat was selectively generated in the adhesive, plastic substrates maintained temperatures lower than the curing temperature of the adhesive. Substrate temperatures as low as 53 °C were observed while the adhesive cured at a target temperature of 85 °C; in contrast, substrate temperatures exceed the adhesive temperatures when using conventional heating methods, such as IR lamps or ovens. The strength of cure was confirmed by mechanical testing; lap shear strengths of RF-cured adhesive joints were 3.26 MPa on average, well above the generally accepted green strength value of 1 MPa required for handling. This RF heating technology offers unique opportunities in industrial manufacturing applications, particularly in the automotive sector where thermoset adhesive bonding is ubiquitous.