Nonfoam Plastic Cushioning Systems

Not all plastic cushioning systems rely on the use of foam. Two major alternatives use air to provide resiliency, but are not foams. In bubble wrap, air bubbles of a defined size and pressure are sealed between two plastic sheets. These materials can be used as wrapping material, or as bags or envelopes. Several different sizes of bubbles are available. The larger sizes are intended for heavier duty applica- 

To select a cushioning system that will protect a product during transportation, it is necessary to know how fragile the product is and the distribution hazards it is likely to be exposed to, as well as the performance characteristics of the cushioning material. 

The information about cushion performance is most often transmitted in the form of characteristic cushion curves that relate the average deceleration to the static loading as a function of drop height, cushion thickness, temperature, and number of impacts (see Fig. 13.2). Computer programs that contain mathematical models of cushion curves for various types of foams, sometimes along with cost information, are also available. Relatively simple calculations then permit selection of an appropriate cushion thickness and load-bearing area that can reasonably be expected to provide adequate protection for a given product. 

In addition to impact forces, transmission of vibrations to the product can result in damage. Characteristic vibration transmissibility plots for foams are also available, which can be matched with the product s susceptibility to damage. Of course, the design process should be followed by the preparation of a model package and suitable testing of the producl/package system, or in case of a very expensive product, a mock-up used with accelerometers to determine actual performance. 

The following example illustrates selection of an appropriate cushion for a product  

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