Rubber foams are divided into two basic types depending on the distribution of gas through the polymer matrix. Closed cell foams are those where the gas bubbles are roughly spherical with polymer walls separating the bubbles. In open cell structures the bubbles are interconnected and a fluid can pass through the material.
Closed Cell Foams
Closed cell foams have characteristics such as buoyancy, water resistance, thermal insulation against extremes of heat and cold. They are resistant to chemicals, oil, petrol and ultra violet light. – Polystyrene foam is one of the most widely used closed cell foams for thermal insulation to coffee cups. It is very buoyant and is used to make life rafts and swimming aids. When applied as part of the substrate under roads it can prevent soil disturbances and surface damage from freezing and thawing. It is stocked generally in sheet thickness between 10mm and 100mm but other thickness can be supplied to order.
– Ethylene vinyl acetate (EVA) is commonly called foam, or expanded, rubber. It is used as padding in sports equipment such as bicycle saddles, ski boots and lightweight sandals. The fishing industry uses it for floats whilst the energy sector uses EVA in photovoltaic cell manufacture to enclose silicon chips.
– Neoprene has a better physical, thermal and chemical resistance than natural foam rubber. It is used widely for wet suits, gaskets and in corrosion resistant coating. Open Cell Foams
Open cell foams are compressible and soft materials that have insulating properties by trapping air inside the gas bubble but allow water and air to pass through them. They work best where a lightweight and soft product is required. Their earliest application was as artificial sponges for personal use and in cleaning vehicles. – Polyurethane foams is used in cushions, seating and carpet underlay. It can also be stocked for use in commercial quality mattresses and shaped pieces of upholstery such as bolsters, backrest, invalid cushions and surface finishes. This foam is produced in different grades. The softest grade is polyether foam. Polyester foams have a more controlled cell structure and can be used for air and gas filtration. Some polyesters are used in water filters in ponds, aquariums and sewage tanks.
– Melamine foams are another type of versatile open cell foam that has a high chemical, abrasion and acoustic resistance. Their physical properties remain constant at a wide range of temperatures and, unlike many plastics, melamine foams remain flexible and do not shatter at very low temperatures. They are used as ceiling tiles and baffles in recording studios. Conclusion
Rubber foams can be manufactured from a wide variety of plastic materials. Foam shapes can be custom built and layered to suit any particular need. They can be designed to have a wide range of physical properties like thermal and acoustic insulation, buoyancy and chemical resistance. AUTHOR BIO
Helen Sharp is a chemical engineer with 25 years of professional experience. She writes widely on the plastics industry for a wide range of websites and blogs. Click here to know more about foam products.