Polymers foams are widely used in a variety of applications, e.g. heat/water/air insulation, impact cushion, vibration absorption. Major foam materials are polyurethane (PU), polystyrene (PS), polyethylene (PE), polypropylene (PP), poly(vinyl chloride) (PVC), polycarbonate (PC); the order is roughly based on the amount of annual consumption.
They can be categorized into open cell and close cell foams as shown in the following Figure.
The comparison between open cell and close cell is shown in the following Table.
Extrusion is the major process to make polymer foams.
Among the manufacturing parameters, the foaming gas is one the critical factors. The following table compares the advantages and disadvantages of different foaming gases.
Reference: Lee L. J. Et al. Composites Science and Technology 65 (2005) 2344-2363