Ideality of pressure-sensitive paint. III. Effect of the base-coat permeability on the luminescence behavior of the sensing layer

Abstract

The response time and temperature dependence of a pressure-sensitive paint (PSP) based on platinum tetra(pentafluorophenyl)porphine (PtTFPP) in the fluoroacrylic polymer FIB significantly increases for bilayer paint systems that include a base coat made of different polymers with solid TiO2 added as scattering agent, compared to the single-layer sensor paint. The temperature dependencies at vacuum are the same in the various bilayer coatings (paint/base coat) as compared to monolayer paint, roughly −0.53%/oC. With FIB base coat the percent of TiO2 is adjusted to reduce photodegradation, in which case only a slight increase in response time (0.6 → 0.8 s) is caused by the base coat and there is almost no change in temperature dependence at 1 atm. However, in the cases of the less permeable polymers, poly(methylmethacrylate) (PMMA) and poly(vinyl acetate) (PVA), there is increased response time of the bilayer coating (rising, respectively, to 15 and 7 s) and significantly greater temperature dependence at 1 atm. The highly impermeable polyacrylonitrile (PAN) as base coat shows little effect on response time but a somewhat higher temperature dependence at 1 atm compared to vacuum. For the highly permeable polydimethylsiloxane (PDMS), adjustment of the TiO2 concentration is needed to prevent an increase in temperature dependence but both PDMS base coats tested have response times < 2 s and low-temperature dependence. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2815–2823, 2000