A study on residual solvent, crystallinity and thermal properties of poly(styrene)-poly(methyl methacrylate)-toluene coatings

Abstract

Drying of poly(styrene)-poly(methyl methacrylate)-toluene coating system has been investigated. The effect of coating composition and initial thickness on the residual solvent, average polymer/solvent concentrations, and coating thickness were studied. The findings revealed that by adjusting the mass fractions of polymers and solvents, the residual solvents and final coating thickness could be reduced to a reasonable level. The residual solvent concentration in poly(styrene)–poly(methyl methacrylate)-toluene coatings did not vary significantly when the concentration of poly(styrene) was altered, but it changed when the concentration of poly(methyl methacrylate) was changed. Additionally, raising the mass percentage of both the polymers had no influence on the glass transition temperature of the coating but significantly limited the diffusion mass transfer. The average concentration of solvent and polymer in these coatings were in agreement with Fickian diffusion over a long period of the total drying time. The findings showed that thick coatings lost the residual solvent at a slower rate for sufficiently long time than the thinner ones. The glass transition temperature of the coatings decreased with the increase in the coating thicknesses. Coating 4 had the highest Tg, i.e., 74.08 °C. No noticeable change was observed in crystallinity of the coatings with the change in the thickness of the coatings. Major crystalline peak with intensity of 100 % in all the coatings were observed in the range 28.8931°–29.3518°. The amorphous nature of the coatings was observed as a broad peak at 20°.