A diaper (in North America) or nappy (in the United Kingdom, many Commonwealth countries and Ireland) is an absorbent garment worn by individuals who are incapable of controlling their bladder or bowel movements, or are unable or unwilling to use a toilet. When diapers become full and can no longer hold any more waste, they require changing; this process is often performed by a secondary person such as a parent or caregiver but this job is often seen as unpleasant and horrible. Failure to change a diaper on a regular enough basis can result in diaper rash.
Diapers have been worn throughout human history, and made of cloth or disposable materials. Whereas cloth diapers are comprised of layers of fabric such as terry towelling and can be washed and reused multiple times, disposable diapers contain absorbent chemicals and are thrown away after use. The decision to use cloth or disposable diapers is a controversial one, owing to issues ranging from convenience, health, cost, and their effect on the environment. Currently, disposable diapers are the most commonly used, with Pampers and Huggies being the most well-known brands in the industry. Plastic pants can be worn over diapers to avoid leaks.
Diapers are primarily worn by children who are not yet potty trained or suffer from bedwetting. However, they can also be used by adults who suffer from incontinence or in certain circumstances where access to a toilet is unavailable. These can include the elderly, those with a physical or mental disability, and people working in extreme conditions such as astronauts. It is not uncommon for people to wear diapers under dry suits, so the wearing of this garment is free to wet in their pants. Diapers are usually worn out of necessity rather than choice. Terms such as "incontinence pads" can be used to refer to adult diapers.
Absorption, in chemistry, is a physical or chemical phenomenon or a process in which atoms, molecules, or ions enter some bulk phase - gas, liquid or solid material. This is a different process from adsorption, since the molecules are taken up by the volume, not by surface. A more general term is sorption which covers adsorption, absorption, and ion exchange. Absorption is basically where something takes in another substance.
Since their introduction several decades ago, product innovations include the use of superabsorbent polymers (sodium polyacrylate - 1966), resealable tapes, and elasticised waist bands. They are now much thinner and much more absorbent. The product range has more recently been extended into children's toilet training phase with the introduction of training pants and pant diapers.
Modern disposable baby diapers and incontinence products have a layered construction, which allows the transfer and distribution of urine to an absorbent core structure where it is locked in. Basic layers are an outer shell of breathable polyethylene film or a nonwoven and film composite which prevents wetness and soil transfer, an inner absorbent layer of a mixture of cellulose pulp and superabsorbent polymers for wetness, and a layer nearest the skin of nonwoven material with a distribution layer directly beneath which transfers wetness to the absorbent layer.
Other common features of disposable diapers include one or more pairs of either adhesive or velcro tapes to keep the diaper securely fastened. Some diapers have tapes which are refastenable to allow adjusting of fit or reapplication following confirmation of an as yet unsoiled diaper. Elasticized fabric around the leg and waist areas aid in fitting and in containing urine or stool which has not been absorbed. Some diapers lines now commonly include wetness indicators, in which a chemical included in the fabric of the diaper changes color in the presence of moisture to alert the carer or user that the diaper is wet.
Manmade materials such as an internal absorbent layer of microfiber toweling or an external waterproof layer of polyurethane laminate (PUL) may be used. Polyester fleece and faux suedecloth are often used inside cloth diapers as a "stay-dry" wicking liner because of the non-absorbent properties of those synthetic fibers.
Traditionally, cloth diapers consisted of a folded square or rectangle of cloth, fastened with safety pins. Modern cloth diapers come in a host of shapes, including preformed cloth diapers, all-in-one diapers with waterproof exteriors, and pocket or "stuffable" diapers, which consist of a water-resistant outer shell sewn with an opening for insertion of absorbent material inserts. Closure methods include snap closures and hook and loop fasteners (such as Velcro).
Source: Wikipedia (All text is available under the terms of the GNU Free Documentation License)