Memory foam

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How memory foam reacts to heat

Memory foam is made from polyurethane with additional chemicals that increase its viscosity level, thereby increasing its density. It is often referred to as visco-elastic polyurethane foam. Depending on the chemicals used and its overall density, it is firmer in cool temperatures and softer when warm. Higher density memory foam reacts to body heat which allows it to mould itself to the shape of a warm body within a few minutes. A lower density memory foam is pressure-sensitive and will mould more quickly to the shape of the body. The example often used to demonstrate its properties is that a hand pressed into the foam and then removed will leave a clear impression in the foam.

History

Memory foam was originally developed in 1966 under a contract by NASA's Ames Research Center as a way to improve the safety of aircraft cushions. Ames scientist Chiharu Kubokawa and Charles A. Yost of the Stencel Aero Engineering Corporation were major contributors to this project. Yost named the temperature-sensitive memory foam 'temper foam'.

Yost later founded Dynamic Systems Inc. in collaboration with NASA to commercialize the foam, including it both medical equipment such as X-ray table pads and sports equipment such as football helmet liners. After Dynamic Systems sold its line of memory foam products to the Edmont-Wilson division of Becton, Dickinson & Co. in 1974, this company expanded to an even wider range of products.

When NASA released memory foam to the public domain in the early 1980s, Fagerdala World Foams was one of the few companies willing to work with the foam, as the manufacturing process remained difficult and unreliable. Their 1991 product, the "Tempur-Pedic Swedish Mattress" eventually led to the international mattress and cushion company, Tempur World. Other companies now based on the foam include Advanced Comfort and Contour-Pedic Sleep Inc.

Memory foam was never used in the space program but was subsequently used medically, for example by patients who used to lie in bed on hard or very firm mattresses for long periods of time without regularly moving such as being bed-bound after a paralyzing stroke. The pressure over some of their bony regions decreased or stopped the blood flow to the region causing pressure sores and/or gangrene. Memory foam mattresses helped hugely to decrease such events.

Memory foam was initially too expensive for general use, but in recent years it has become cheaper to produce and is now widely available. Its most common domestic uses are mattresses, pillows, and mattress toppers. It still has medical uses, such as wheelchair seat cushions, hospital bed pillows and padding for persons suffering long-term pain or postural problems; for example, a memory foam cervical pillow may alleviate chronic neck pain. Its heat-retaining properties may help some pain sufferers who find the added warmth helps to decrease the pain.

Properties

A memory foam mattress is usually denser than an ordinary foam mattress. This makes it more supportive but also heavier. It is often seen as a good compromise between the comfort of a soft mattress and the supportiveness of a firm one. Memory foam mattresses often sell for more money than traditional mattresses but they may last longer due to their resistance to parasites such as dust mites.

The property of firmness (hard to soft) of memory foam is used in determining comfort. Firmness is measured by a foam's IFD (Indentation Force Deflection) rating.

IFD measures the force (in pounds) required to make a dent 1 inch into a foam sample 15" x 15" x 4" by a 8 inch diameter (50 sq in) disc - known as IFD @ 25% compression. IFD ratings for memory foams range between super soft (IFD 10) and semi-rigid (IFD 12). Most memory foam mattresses are firm (IFD 12 to IFD 16).

Some report that IFD is a poor way to measure softness of memory foam, and that foam density as a measure of quality is more important . Foam density of 5 lbs per cubic foot (80 kg/m3) or greater is considered high quality. Although most standard memory foam is 1-3 lbs per square inch

Hazards

When new, some memory foams give off a distinct chemical odor which many people find unpleasant which some say is akin to the smell of paint. This odor decreases with airing, but some people remain sensitive to it. Emissions from memory foam mattresses may cause more respiratory irritation than other mattresses. Mildew and house dust mites may not occur as frequently so asthma attacks may be less frequent and severe

Memory foam, like other polyurethane products, can be combustible. State and US Federal Laws have been enacted in the USA to require all bedding, including memory foam items, be resistant to ignition from an open flame such as a candle or cigarette lighter. There has been some concern that high levels of the fire retardant PBDE, commonly used in memory foam, could cause health problems for users of memory foam bedding products.

External links

• memory foam mattress topper
• Polyurethane Foam Association
• Memory Foam Reviews and Guides
• U.S. Memory Foam Mattress Toppers & Pillows

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