A HIGH AIRFLOW DRYING EXPERIMENTAL SET-UP TO STUDY DRYING BEHAVIOR OF POLYMER SOLVENT COATINGS

Abstract

A High Airflow Drying Experimental Set-up (HADES) has been constructed to simulate conditions encountered in industrial dryers. In this experiment the drying gas flows parallel to the coating in a narrow gap (6 × 10⁻³ cm). Measured heat transfer coefficients (HTCs) on HADES range from 7 W/m² K at 0.072 m/s to 26 W/m² K at 0.72 m/s. The range of HTCs could easily be extended by using higher gas flow rates or narrower gap. The drying results obtained in HADES compare well with model predictions for poly (vinyl acetate)/toluene and show expected trends for changes in drying temperature and flow rate. Experimental drying results for poly (methyl methacrylate)/acetone show an anomalous drying behavior where residual solvent content is minimized at intermediate drying gas flow rate. This phenomenon is likely due to formation of a glassy skin at the surface of the drying coating.

Keywords:

• Coatings
• Drying
• Polymers
• Skinning

ACKNOWLEDGMENTS

We thank 3M and Avery Denison for their financial support for this project. Thanks are also due to Dan Luu and George Carenzo for their ideas in the design of drying chamber of HADES.