Glassy polymer coatings characterised

Glassy polymer coatings were characterised using a quantitative method for quartz crystal microbalance (QCM). Source: Olivier-Fotolia.com

Researchers from Northwestern University, Illinois, together with partners from Ford Motor Company and Boeing describe in a technical paper a quantitative method for using the quartz crystal microbalance (QCM). The aim is to characterise the high frequency viscoelastic response of glassy polymer coatings with thicknesses in the 510 µm regime. Measuring the frequency and dissipation at the fundamental resonant frequency (5 MHz) and at the third harmonic (15 MHz), resulted in three independent quantities. For coatings with a predominantly elastic response, characterised by relatively low phase angles, these quantities are the mass per unit area of the coating, the density-shear modulus product, and the phase angle itself. The approach was demonstrated with a model polyurethane coating, where the evolution of these properties as a function of cure time was investigated. For fully cured films, data obtained from the QCM are in good agreement with results obtained from traditional dynamic mechanical analysis. The paper appeared in the "Langmuir" Journal, Vol. 27, 2011, pp. 9873-9879.