Memory foam

This effect is generated by the deformed porous material pushing outwards to restore its structure against an applied pressure.

Smaller pores lead to higher internal surface area and reduced air flow, increasing the adhesion and pneumatic effects.

Denser cell structure can also resist the penetration of water vapor, leading to reduced weathering and better durability and overall appearance.

[4] Memory foam was developed in 1966 under a contract by NASA's Ames Research Center to improve the safety of aircraft cushions.

[5] Created by feeding gas into a polymer matrix, it had an open-cell solid structure that matched pressure against it, yet slowly returned to its original shape.

It has medical uses, such as wheelchair seat cushions, hospital bed pillows and padding for people suffering long-term pain or postural problems.

Heat retention can be a disadvantage when used in mattresses and pillows, so in second-generation memory foam, companies began using open cell structure to improve breathability.

Gel-infused memory foam was next developed with what were described as "beads" containing the gel which, as a phase-change material, achieved the desired temperature stabilization or cooling effect by changing from a solid to a liquid "state" within the capsule.

Aloe vera, green tea extract and activated charcoal have been combined with it to reduce odors and even provide aromatherapy while sleeping.

Rayon has been used in woven mattress covers over memory foam beds to wick moisture away from the body to increase comfort.

Polyethylene terephthalate, one such polymeric material, provides certain benefits over polyurethane, such as recyclability, lightness, and thermal insulation.

[14] Laws in several jurisdictions have been enacted to require that all bedding, including memory foam items, be resistant to ignition from an open flame such as a candle or cigarette lighter.

[15] There is concern that high levels of the fire retardant PBDE commonly used in memory foam could cause health problems for some users.

Manufacturers caution about leaving babies and small children unattended on memory foam mattresses, as they may find it difficult to turn over and may suffocate.

The effects of chronic (long-term) exposure to methylene chloride in humans involve the central nervous system, and include headaches, dizziness, nausea, and memory loss.