Designing of biodegradable polycaprolactone: Binary and ternary coatings to minimize the defects and cost of solvent(s)

Abstract

AbstractCoatings of polycaprolactone (PCL) in methylene chloride and toluene were prepared using solution casting method. Coatings of two different polymer mass percentages (5% and 10%), and thicknesses (800 and 1600 μm) were prepared. A drying study on PCL‐methylene chloride‐toluene coatings was carried out. The binary coatings of PCL‐methylene chloride and PCL‐toluene served as control cases. The results showed that the drying behavior was external mass transfer controlled for the binary coatings but diffusion controlled for the ternary coatings for most of the drying period. The drying rate enhanced but residual solvent increased with the progressive increase in initial concentration of methylene chloride and decrease in initial concentration of toluene. This shows that the drying rate can be enhanced by partially replacing the costly solvent with cheaper one, that is, toluene with methylene chloride. The coatings were characterized by scanning electron microscopy to understand the surface morphology. The scanning electron microscopy results further indicate that replacing toluene with methylene chloride caused disappearance of cracks, wrinkles, and phase‐separation. The coatings with high initial content of methylene chloride were smooth and dense, and more residual solvent content does not manifest in coating defects. Hence, replacement of toluene with methylene chloride leads to savings on material and energy costs for drying along with better quality coatings.