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Memory foam was originally developed by NASA to ease the pressure of extreme G-force during space shuttle take off. It was never used in the space program, but was subsequently used in medical applications, for example with patients suffering from pressure sores or bed-bound for a long period.
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 applications are mattresses, pillows and mattress toppers (also known as mattress pads). It remains useful in medical-related 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 are also helpful to some pain sufferers, who find the added warmth helps alleviate pain.
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 than traditional mattresses but they last longer.
When new, memory foam often gives off a distinct chemical odor which many people find unpleasant. This fades with airing, but some people remain sensitive to it.
The hardness or softness of memory foam plays an important role in ensuring comfort. Its firmness is determined by its IFD rating. Indentation Force Deflection measures the amount of force, in pounds, required to indent a 50 inch disc into a 15"x15"x4" viscoelastic foam sample and make a 1" indentation. This is commonly known as IFD @ 25% compression. IFD ratings for memory foam range between super soft (10) and semi-rigid (120). Most memory foam mattresses are 12-16 IFD firm.
This article was copied from Memory foam :From Wikipedia