Principles of developing physical test methods for disposable consumer products

Abstract Strength, softness, and absorbency have been identified as the key attributes for disposable consumer products such as tissue, towel and diapers. These attributes are generally evaluated subjectively by users. Although subjective evaluation may be necessary for developing such consumer products, it is time-consuming and expensive. More importantly, it seldom provides guidance or direction regarding process control or product development. The main reason is because subjective evaluation is performed after the fact (ex post facto), not before the event (not ex ante). Accordingly, it has been desirable to develop physical test methods to predict in-use performance of a consumer product. In developing physical test methods to link with subjective evaluation, reliable and relevant subjective data is necessary. Developing physical test methods for softness of hygiene paper has been extremely challenging. The objective of this paper is to demonstrate a feasibility of developing physical test methods which can be highly related to subjective evaluation. To this end, it is hypothesized that tissue softness mainly consists of bulk softness and surface softness. It is assumed that the bulk softness should be determined from bulk stiffness which is defined as the slope between the two specified points in a load-elongation curve from tensile testing. It is also assumed that the surface softness should be determined from the surface properties (roughness and friction) from a surface tester (e. g., Model: KES-SESRU. Kato Tech, Japan). It is suggested that the principles used here for developing physical test methods for tissue softness should be also applicable to other physical properties such as strength and absorbency.