The Effect of Substrate Porosity and Method of Drying on Coating Gloss

This thesis involved the study of the effects on gloss, smoothness, sizing, and ink holdout of average pore size and drying method for styrene butadiene, polyvinyl acetate, and acrylic bound pigmented coatings. Average pore size was varied by using four different substrates. A mylar film with 0 micron average size and Millipore filter papers with .22, .45, and .80 micron average pore size were used. The three drying methods used were back drying on a hot plate, air drying, and blow drying with hot air. It was found that the styrene butadiene coating gave the best gloss development, the smoothest sheet, the best sizing, bu the worst ink holdout. The polyvinyl acetate coating gave the second best gloss, smoothness, and sizing but the best ink holdout. The uncalendered gloss increased linearly from 3-4% between .22 and .80 microns average pore size. The gloss of the calendered sheets increased from .22 to .45 microns then decreased similarly from .45 to .80 microns. Blow drying gave the highest gloss followed by air drying then back drying. The smoothness was unaffected by changing pore size for the uncalendered sheets. The Parker Print Surf smoothness tester results showed that smoothness increased as average pore size increased and smoothness increased after calendering. The Sheffield smoothness tester gave quite different results. The Sheffield smoothness decreased as average pore size increased and decreased after calendering. Back drying gave the smoothest sheet followed by air drying and blow drying. The only conclusions that can be drawn about sizing are that it decreased after calendering and polyvinyl acetate gave the best sizing followed by acrylic latex then styrene butadiene. The ink holdout slightly decreased until about .45 micron average pore size then increased at a similar rate back to the initial value. Back drying gave the best ink holdout and blow drying gave the worst. Polyvinyl acetate gave the best holdout and styrene butadiene gave the worst