Why Diapers Are Amazing
A disposable diaper’s quality is so important that hygiene and comfort depends on it to provide both baby and mom with a happy disposition. It is so compact and efficient, a mother can’t help wonder:
What’s in a diaper?
1) Polyethylene or cloth-like film: This is used as the back sheet, that prevents the liquids from leaking out of the diaper.
2) Tissue: A special tissue paper that is different from the regular bathroom tissue and has a higher elasticity and wet strength is another important component of a diaper. The tissue essentially serves as a carrier for the pad (the pad is the absorbent core of the diaper) and helps reduce the pin holes created during the compression process carried out by continuous drum forming systems.
3) Adhesives: Three types of adhesives are used: a construction adhesive, for the back sheet and the non-wovens, an elastomeric adhesive, for the leg and waist foam elastics, and a specialty adhesive known as “pad integrity adhesive” is also used to add strength to the diaper core when it is wet.
4) Hydrophobic Non-woven: It is used as a top sheet for the leg cuffs; it prevents water from passing through. It is made of polypropylene resin without any added surface surfactants. The hydrophobic non-woven prevents leakage out of diaper.
5) Hydrophilic Non-woven: It is the main top sheet, the top surface that is in contact with the baby’s skin. It allows the liquids to flow into the diaper core. The difference between the two non-wovens (philic and phobic) is the surfactant treatment used in the process. The surfactant treatment reduces the surface tension of the non-woven, reduces the contact angle with the liquid and allows it to pass. Flow dynamics within the diaper core prevent liquids from returning to the surface. Non-wovens used in diapers are made with the spun bonding process, which makes the diaper core soft, lofty, and resistant.
6) Elastics: Used to improve the fit of the diaper, usually made of polyurethane or polyester foam, synthetic rubber or Lycra® (also known with the generic name Spandex). They are used in cuffs, for the waist and the legs; they can also be used as lateral side panels and in tape construction. Most gasket cuffs use spandex to provide a seal with the baby’s legs. Spandex can stretch as much as 400% of its original length before it breaks, however it is typically used at less than 300% stretch. New generations of softer and stronger elastic materials are reportedly in the pipeline.
7) Lateral Tapes: In premium diapers, Velcro type materials have been used to provide mechanical grip, it is also known as the “hook tape”. There are new versions of elasticized Non-woven Velcro Tapes.
8) Frontal Tapes: This is used to facilitate multiple repositioning of the lateral tape without tearing the back-sheet, it is made of polypropylene film and attached to the front of the diaper with adhesive. Its use has helped to reduce the thickness of the poly film without the risk of potential tears associated with the opening of the lateral tapes from the backsheet. In premium diapers, a special loop system has been developed in order to use of Velcro type fasteners (also called the “hook and loop” system). This loop tape can use a “locked loop” or a “brushed loop” in order to provide a softer texture or a stronger grip.
9) Cellulose: Used in the construction of the pad, it gives integrity and absorbing capacity to the diaper. The capacity of normal cellulose pulp is around 10 cc of water per gram of pulp when the diaper is in “free swell” but less than 2 cc when subjected to 5 KPa of pressure; that is why a super absorbent material is also needed to hold the liquids under pressure.
10) Acquisition and Distribution Layer: Also known with its abbreviation ADL, it is a sub layer used between the top sheet and the absorbent core. Sometimes used in full length but mostly preferred as a patch near the target zone where urine is most likely to be deposited. This sub layer is specially needed when the absorbent core is very thin -the sub layer quickly moves liquids into the absorbent core and reduces potential leakage. The ADL is very important to provide a sense of dryness to the skin, providing additional separation between the wet pad and the skin. ADL’s should be used whenever the mix of SAP in the absorbent core exceeds about 15% by weight or when the liquid penetration time requires a boost in order to avoid diaper leakage due to liquid accumulation inside the diaper.
11) Sodium Polyacrylate: Also known as super-absorbent or “SAP” (super absorbent polymer), Kimberly Clark used to call it SAM (super absorbent material). It is typically used in fine granular form (like table salt). It helps improve capacity for better retention in a disposable diaper, allowing the product to be thinner with improved performance and less usage of pine fluff pulp. The polymer has cross-links, which effectively leads to a three-dimensional structure. It has high molecular weight of more than a million; thus, instead of getting dissolved, it solidifies into a gel.