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.

Contents

1 History

2 Hazards

3 References

4 External links


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History

Memory foam was originally developed by NASA to decrease the very high pressure caused by the extreme g-force occurring during the take-off of the space shuttle.[citation needed] It 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[citation needed], 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.[citation needed]

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.[citation needed]

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 or greater is considered high quality.

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.

References

^ Make your own memory foam bed

^ Anderson RC, Anderson JH, Respiratory toxicity of mattress emissions in mice, Archives of Environmental Health, Jan-Feb 2000

^ Memory Foam MSDS Sheet

^ California Bureau of Home Furnishings and Thermal Insulation

^ Arlene Blum The Fire Retardant Dilemma, 12 Oct. 2007

External links

Polyurethane Foam Association

Memory Foam Reviews and Guides

Categories: Polyurethanes | Foams | Non-Newtonian fluids | Bedding

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