Physical and chemical properties of the fibers have obvious impact on the characteristics of the nonwoven products and their use performance. It is always worth it to be able to predict and quantify these relationships when selecting appropriate fiber raw materials and designing new products. There is much useful science behind this, which has been generated by specialists focused on specific areas of web-forming technologies. Sometimes however, it is helpful to tap into the existing knowledge in other areas. For example, some principles of fiber physics which are well known and commonly used in traditional paper-making may be of value to nonwovens structures produced via different forming techniques. For instance, one of basic equations in paper science and technology is Page formula (Fig. 4) describing the effect of individual fiber and fiber-to-fiber bond characteristics on the mechanical properties of paper. This equation is probably not well known among the nonwoven experts but may prove useful for example in the case of latex-bonded airlaids.
Fig. 4. Page equation for predicting tensile strength of paper (T) – can be used for some nonwovens.
The science of porous materials such as rocks and soil has been applied in various ways to an ostensibly remote area of fiber networks in order to quantify their pore size, porosity and permeability characteristics. This generated new knowledge proved to be of great importance for predicting the dynamics of fluid flow and fluid placement in absorbent materials in personal hygiene applications. In turn, this led to developing often simple mathematical equations helpful in assessing the effect of fiber geometry on the porous structure of loose or bonded fiber webs (Fig. 5).
Fig. 5. Fiber geometry – impact on porous characteristics of fiber network.