Gases and Vapor Permeability to Carnauba and Shellac Coatings

Abstract

Study on gases and vapor permcahility to carnauha and shellac using tangerines as tested fruit showed that Oxygen and carbon dioxide permeated to carnauha readily. The internal gas composition as well as ethanol content of tangerine juice were only slightly altered. However. the permeability of the gases were restricted in shellac resulting in accumulation of ethanol. On the opposite, water vapor permeated to shellac better than earnauba. Shellac reduced water loss only upto 30% at 20% shellac concentration, while carnauha reduced water loss by as much as 60% at 15% carnauba concentration. The properties of mixed coating were in between the properties of each material alone. However, shellac had stronger influence than carnauba on the vapor permmeability of the mixture. Study for gases and vapor permeability, by coating both materials on silk-screen revealed that permeability depended also on the adhesion of the waxes to the coating surface.