Baby Diapers
The Center for Baby and Adult Hygiene Products is the only U.S.-based organization dedicated to advancing the personal absorbent hygiene products industry in North America
How Diapers Are Made
Disposable diapers are made from common materials that have a long history of safe use in a variety of everyday consumer products. An average diaper weighs between 1.4 and 1.8 ounces and is primarily made of cellulose, polypropylene, polyethylene and a super absorbent polymer, as well as minor amounts of tapes, elastics and adhesive materials. Advances in each of these materials have enabled diapers to become lighter, thinner and more effective – with less of an impact on the environment.
Since becoming broadly available in the 1960s, disposable diapers have gone through a number of changes in materials used for diaper construction to improve their performance, fit, and skin comfort. In recent years these advances have also reduced diapers’ environmental impact.
Parts of a diaper
Each diaper has two primary parts:
Diaper core – the middle of the diaper where urine and liquid stool are absorbed and stored.
Diaper chassis – the shell of the diaper holds the core together, attaches the diaper onto the baby, and creates a proper fit around the legs.
Diaper Core
The core is primarily composed of polypropylene, cellulose and a superabsorbent polymer.
Topsheet
The topsheet is the part of the diaper which comes in contact with the baby’s skin. It has been specially designed to quickly transfer fluids to the core while remaining soft and dry to the touch. Some topsheets include a skin-care lotion, such as those found in diaper skin-care products, which can protect the skin from over hydration and reduce irritation.Acquisition/Distribution Layer
This layer is immediately under the topsheet of the diaper. It moves liquid away from the baby’s skin and distributes it more evenly across the entire diaper core for better absorbency. The biggest design improvement was the development, in the 1980s, of superabsorbent polymers that can absorb many times their weight in fluids. Children’s skin health has improved because these polymers lock moisture away where it cannot irritate skin. The severity and frequency of diaper rash has declined dramatically. As technology has improved, less and less cellulose has been needed. This allows major reductions in diaper weight and volume, resulting in a reduced environmental impact.Absorbent Core
The absorbent core is the inner-most layer of the diaper. It typically consists of a blend of cellulose fluff pulp and polyacrylate granules. The cellulose portion quickly absorbs and transfers urine to the polyacrylate superabsorbent material, where it is trapped. This keeps the baby’s skin dry, even if he or she sits on a full diaper.
The biggest design improvement was the development, in the 1980s, of superabsorbent polymers that can absorb from several tens to several hundred times their weight in fluids. Children’s skin health has improved because these polymers lock moisture away where it cannot irritate skin. The severity and frequency of diaper rash has declined dramatically. As technology has improved, less and less cellulose has been needed. This allows major reductions in diaper weight and volume, resulting in a reduced environmental impact.
Diaper Chassis
The chassis is made up of the backsheet plus additional features that ensure the diaper fits well. These features can include stretch side panels, fastening systems and tapes, and leg cuffs.
Backsheet
The backsheet is the water-resistant outer layer of the diaper and it prevents liquids from passing through the diaper and leaking onto the baby’s clothing or surrounding environment. The polyethylene backsheet can be made with a structure that allows water vapor and air (but not liquids) to pass through, reducing moisture and keeping the skin drier.
Fit and Comfort Features
Materials and specific designs that help diapers fit well vary according to manufacturer, but they all perform the same basic functions. Important design elements often include stretch side panels and fastening systems that enable the diaper to be pulled snug against the baby’s torso to prevent leakages top. Elastics and cuffs on the diaper’s sides ensure improved fit around the legs and prevent leakage.
Additional Materials
In both the diaper core and chassis, small amounts of adhesives are used to bond component parts together to ensure performance, fit, and overall integrity. In some products, features such as designs or scents may be added.
Colors in Diapers
Colors are frequently added to disposable diapers to enhance the diapering experience. This could include their use to indicate the diaper’s orientation, highlight the diaper’s functional areas, drive consumer or child interest, or convey diaper wetness. General consumer concerns related to the use of colors in diapers has often been associated with disperse dyes, some of which are known sensitizers. The facts are: Disperse dyes are not used in the disposable diapers manufactured by BAHP member companies. The colors in use are non-irritating and non-sensitizing pigments with favorable safety profiles. Numerous safety tests of pigments used in diapers, such as skin patch tests, have confirmed their safety and have shown no evidence of skin irritation or sensitization. These pigments are commonly- and safely-used in a wide range of products including textiles, toys, school chalk and crayons, and food packaging. Through pigment selection and product design, the colors in use are intended to remain bound to the diaper and to provide their intended design and function whether the diaper is wet or dry.
Where are the Colors in the Diaper?
Diapers can have designs on the Outside (Exterior, or Diaper Chassis) and/or the Inside (Interior, or Diaper Core), which may also help designate the superabsorbent areas. Some diapers feature wetness indicators based on colors in the shape of strips or designs that undergo a change in color or fade when the diapers are wet. To help illustrate the difference, refer to the Parts of a Diaper information on this website, as also highlighted in the picture below:
Outside Use of Colors:
Colors on the exterior of the Diaper Chassis are most often printed on the waterproof breathable backsheet, or the polypropylene nonwoven fiber web that covers the backsheet, which typically is the external-most layer of the diaper. Colors may be printed directly on the front or back surface of the nonwoven web.
Inside Use of Colors:
Like colors applied to the outside layers, colors on the interior of the Diaper Core are bound to the applied fibers. As such, they do not release from the nonwoven polymeric material. Even when the diapers are full, pigments remain bound with the polymeric material and are not expected to release.
All colors used in the disposable diapers manufactured by BAHP member companies are non-irritating and non-sensitizing pigments that are evaluated for safety according to the same principles as all other materials which comprise the diaper. The colors also are tested both wet and dry to assure color-fastness, which determines their inability to come off the diaper and potentially transfer to the skin.
Safety of Colors in Diapers
Colors used in diapers have a very favorable safety profile and are not considered skin sensitizers. Diaper colors undergo comprehensive safety evaluations including human skin patch tests. Even after repeated direct topical applications within such safety studies, the colors have not demonstrated human skin irritation or sensitization.
Additional Information on Colors in Diapers
For more information about the safety of colors in disposable diapers go to clinical pediatrics article Evans, Eric B., et al. “Colors in Disposable Diapers Addressing Myths.” Clinical pediatrics (2014): 0009922814540379.
Innovative Materials & Design
Specific materials in modern disposable diapers are designed to control the main factors which cause diaper rash.
Materials Used in Diapers
| Material | Where Used in Diapers |
|---|---|
| Polypropylene (PP) | Primarily used for the topsheet, the part of the diaper next to baby’s skin, tapes and fastening system |
| Polyethylene (PE) | Primarily used for the backsheet, the outer cover, tapes, and fastening systems |
| Cellulose fluff pulp | Absorbent core and core tissue |
| Superabsorbent polymer | Absorbent core |
| Elastics | Along leg opening and waist to improve fit. |
| Adhesives | Throughout the diaper to bond various other materials together |
Superabsorbent Polymers
Historically, diapers used fluff pulp, made of cellulose derived from wood, as the sole absorbent material in the core. Fluff pulp was good at absorbing wetness, but not good at keeping it away from the baby’s skin. It is also easily saturated, making it unable to absorb additional urine.
Today, superabsorbent materials are used in most of the diapers sold throughout the world. These superabsorbent polymers can absorb from several tens to several hundred times their weight in fluids. Typically 1 gram of superabsorbent material in a diaper can absorbs at least 35g of urine. By contrast, 1 gram of pulp absorbs approximately 10g of urine.
A small amount of modified fluff pulp is used in the diaper core to initially absorb the urine, and pull it into to the polymer material for final storage. Once absorbed the wetness cannot be squeezed back out towards the skin by the pressures exerted by a sitting or moving infant. Over time, superabsorbent materials have been designed to absorb more urine and absorb it more quickly, minimizing the time that wetness contacts the skin.
Topsheets
The topsheet is the layer that comes in contact with the child’s skin. It is specially designed to quickly pass fluids through to the superabsorbent layer, while remaining soft and dry to the touch. Some topsheets may include a lotion, similar to those found in diaper skin-care products, to further protect the skin from over-hydration and irritation.
*All information on this page is a general description and may not precisely reflect the products of our member companies.*