The fundamental absorbency mechanisms of hygiene paper

A hygiene paper is characterized by having low density and low basis weight (i.e., weight per area). Its main constituent is cellulose fiber, known as pulp. Since hygiene paper including tissue (i.e., bathroom- and facial-tissue), paper towel, and napkins has low density and low basis weight, it is thin like a paper sheet. A hygiene paper requires good softness, strength, and absorbency. With regards to absorbency. a hygiene paper should be able to pick up liquid spills as fast as possible before it is disposed of. In short, its lifetime is extremely short, lasting only for a few seconds. The Lucas-Washburn theory has been validated from the absorbency data of some com-mercial tissue products available in the patent literature. The theory suggests that absorbency amount (Q) should be proportional to the square root of time. t1/2, in a plot of Q against t,/2. Such a plot is referred to as the Lucas-Washburn plot and the slope is known as the Lucas-Washburn slope, K. A higher value of K indicates a higher speed of absorption. The slope. K. is a function of the surface tension and the viscosity of the liquid, the wettability of the solid surface by the liquid, and the porous structure of the product. The wettability depends on the surface roughness (or profile) and the surface heterogeneity. It is recognized that the absorbency should depend on the absorbency measurement methods employed. Although many absorbency measurement methods have been implemented, only a few have been standardized. The standardization of absorbency test methods is necessary to compare the products objectively without ambiguity.