Date of Award

12-1973

Degree Name

Bachelor of Science

Department

Paper Science and Engineering

Abstract

Numerous works have been done on the investigation of coat weight variations by various researchers. The mechanism of the variation, in a given base stock, is explained by the two models - the hydrodynamic pressure which is a strong function of the web speed, and the visco-elastic or normal force. For a given coating color, viscosity is a function of the web speed which causes the shearing action to take place. Increasing the speed will cause an increase in hydrodynamic pressure as well as visco-elasticity, which tend to lift up the blade and thus a higher coat weight will be obtained. However, speed will alter the time interval available for coating penetration and this acts to reduce the coating weight. The combination of these two effects governs the coat weight variation almost entirely. It is found that at low blade pressure, the increase in coat weight with respect to speed is rapid and great. However, the increase is lowered with higher blade pressure. At extremely high speed and low pressure, the coat weight is found to be decreased somehow. The relationship between the coat weight and the speed of web is so important that it enables one to predict the effect of one on the other.

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