No abstract

The efficiency of radiative powder coatings curing depends both on the coating radiative properties and the spectral emissivities of the infrared emitters. This investigation is structured to develop a mathematical model using the radiative properties of the coating to describe precisely the coating temperature and deduce the degree of polymerization conversion during the cure. The reflectance measurements results obtained with a FTIR equipped with an integrating sphere are analyzed and implemented in a thermal model. These results show that reflectance values vary with the chemical composition, the pigment nature, and are influenced by the powder coatings cure. The thermal model, solved with the finite volume method, permits to compute the varying temperature within the thickness of the powder-coated metal sample and provides a good prediction of the temperature within the ''coating + substrate'' system. The experimental cure of powder coatings supporting this study was performed in a small test oven equipped with electrical infrared emitters.Heat capacity (J kg -1 K -1 ) e Thickness (m) E Activation energy (J mole -1 ) hConvective exchange coefficient DH 0 Total specific heat of the polymerization reaction (W m -2 K -1 ) kArrhenius parameter (J s) k 0Pre-exponentiel factor (J kg -1 ) m, nOrder of reaction (s -1 ) Q reaction Energy released by the exothermal polymerization reaction R Universal gas constant (W m -2 ) T Temperature (J mol -1 K -1 ) xConversion degree (K)Greek symbols a Absorption coefficient e Emissivity / Radiative flux (W m -2 ) k c Thermal conductivity (W m -1 K -1 ) k Wavelength (lm) q à Hemispherical reflectance q Density (kg m -3 ) sTransmission coefficient r Stefan-Boltzmann constant (W m -2 K -4 )Subscripts em Infrared emitter surf Surface