Convoluted foam is a synthetic textile made from polyethylene that is used as protective packaging and lining material for a variety of products. It is initially produced in flat sheets that are anywhere from one to eight inches in thickness (2.54 cm to 20.32 cm), which are then saturated with a thermosetting resin, such as trimethylol melamine or benzoguanamine. The sheets are then passed through a machine that convolutes one side with special die cutters, creating the characteristic egg crate pattern. The sheets are then cut in half to obtain two sheets that are compressed with this pattern on only one side so that they may be nested in pairs. The nested pairs are then treated with ethylene-acrylic acid or butene-maleic anhydride, cross-linking copolymers that react with the thermosetting resin to produce enough rigidity that the foam may stand on its own.
This patterned foam is known by many other names since it has so many applications. For example, it is commonly referred to as acoustical convoluted foam because it is used to absorb sound. When affixed to walls and other surfaces, the unique hills and valleys in the machined pattern trap sound waves in the low-to-mid frequency range up to four times more effectively than regular flat foam. This makes convoluted foam very useful when noise reduction or privacy is desired. In fact, this foam can often be seen lining the interior of music studios, machine shops, offices, and computer labs.
Another common use of this material is in the manufacturing of bed pillows and mattress toppers. For one thing, the unique pattern provides more cushion than flat foam since the coned peaks absorb physical stress and provide for better weight distribution. The material also permits more air circulation, and many hospitals use medical grade convoluted foam as bedding material to reduce the risk of decubitus ulcers, or bedsores.
Convoluted foam is also a superior packing material. Due to its cone-shaped pattern and ability to nest, products can be completely encapsulated when wrapped for shipping to help resist movement during transport. Some manufacturers of convoluted polyethylene foam make an anti-static variety as packing material for computer and other electronic components. The foam can also be cut to custom fit any product, and is available in a variety of densities and colors.