Evaluation of Two Simplified Methods for Determining Cushion Curves of Closed Cell Foams

Autores UPV
Año
Revista PACKAGING TECHNOLOGY AND SCIENCE

Abstract

Because of the negative environmental impact of using traditional polymeric materials for cushioning in protective packaging, the interest in optimization of cushion design resulting in replacement or reduction of the amount of cushioning materials has increased in recent years. It has been generally accepted that the shock absorbing characteristics for cushioning materials are presented as the so-called cushion curves, i.e. graphs of peak acceleration of shocks versus the corresponding static stress, presented over a range of static stress conditions for a specific material thickness and at a specific drop height. The cushion curves are mainly used to design and optimize cushion packaging. This information is specific to each packaging manufacturer, particular chemical formulation and manufacturing process. The traditional method to obtain cushion curves of a specific material is described in ASTM D1596, but this method requires enormous amounts of test data, is time consuming and expensive. For this reason, cushion curves provided by manufacturers are rarely updated and often are obsolete. In recent years, alternative methods have been developed to obtain cushion curves in a significantly shorter time required for testing. To achieve a wide use of these methods, it is necessary to know their accuracy in comparison with the ASTM D1596 method. The objective of this paper is to compare two of those alternative methods with the standard ASTM D1596 method, by applying them to obtain the cushion curves of two typical cushioning materials. More specifically, the single compression data method developed by Sek et al. and the stress-energy method (dynamic stress versus dynamic energy) developed by Burgess were applied to obtain cushion curves for expanded polystyrene with density 15 kg/m 3 and for polyethylene Ethafoam¿ (Modisprem S.A. Zaragoza, Spain) with density 29 kg/m 3 and are presented in this paper. The effectiveness of these alternative methods for developing cushion curves and their advantages, disadvantages and limitations are discussed. Copyright © 2011 John Wiley & Sons, Ltd.