Portions of these chemical "ropes" are designed to interact with water molecules. Other parts of the polymer have the ability to chemically link with different polymer molecules in a process known as cross linking. When a large number of these polymeric chains are cross linked, they form a gel network that is not water soluble but that can absorb vast amounts of water.
Polymers with this ability are referred to as hydrogels, superabsorbents, or hydrocolloids. Depending on the degree of cross linking, the strength of the gel network can be varied.
This is an important property because gel strength is related to the tendency of the polymer to deform or flow under stress. If the strength is too high the polymer will not retain enough water. If it too low the polymer will deform too easily, and the outermost particles in the pad will absorb water too quickly, forming a gel that blocks water from reaching the inner pad particles. This problem, known as gel blocking, can be overcome by dispersing wood pulp fibers throughout the polymer matrix.
These wood fibers act as thousands of tiny straws which suck up water faster and disperse it through the matrix more efficiently to avoid gel blocking. Manufacturers have optimized the combinations of polymer and fibrous material to yield the most efficient absorbency possible. The absorbent pad is at the core of the diaper. It is held in place by nonwoven fabric sheets that form the body of the diaper.
Nonwoven fabrics are different from traditional fabrics because of the way they are made. Traditional fabrics are made by weaving together fibers of silk, cotton, polyester, wool, etc. Nonwovens are typically made from plastic resins, such as nylon, polyester, polyethylene, or polypropylene, and are assembled by mechanically, chemically, or thermally interlocking the plastic fibers. There are two primary methods of assembling nonwovens, the wet laid process and the dry laid process.
A dry laid process, such as the "meltblown" method, is typically used to make nonwoven diaper fabrics. In this method the plastic resin is melted and extruded, or forced, through tiny holes by air pressure. As the air-blown stream of fibers cools, the fibers condense onto a sheet.
Heated rollers are then used to flatten the fibers and bond them together. Polypropylene is typically the material used for the permeable top sheet, while polyethylene is the resin of choice for the non-permeable back sheet.
There are a variety of other ancillary components, such as elastic threads, hot melt adhesives, strips of tape or other closures, and inks used for printing decorations. The bottom of the conveyor is perforated, and as the pad material is sprayed onto the belt, a vacuum is applied from below so that the fibers are pulled down to form a flat pad.
At least two methods have been employed to incorporate absorbent polymers into the pad. In one method the polymer is injected into the same feed stock that supplies the fibers.
This method produces a pad that has absorbent polymer dispersed evenly throughout its entire length, width, and thickness. The problems associated with method are that loss of absorbent may occur because the fine particles are pulled through the perforations in the conveyor by the vacuum.
It is therefore expensive and messy. This method also causes the pad to absorb unevenly since absorbent is lost from only one side and not the other. A second method of applying polymer and fiber involves application of the absorbent material onto the top surface of the pad after it has been formed.
This method produces a pad which has absorbent material concentrated on its top side and does not have much absorbency throughout the pad. Another disadvantage is that a pad made in this way may lose some of the polymer applied to its surface. Furthermore, this approach tends to cause gel blocking, since all the absorbent is on the outside of the pad. The moisture gets trapped in this outer layer and does not have a chance to diffuse to the center.
This blockage holds moisture against the skin and can lead to discomfort for the wearer. These problems are solved by controlling the mixture polymer and fibrous material. Multiple spray dispensers are used to apply several layers of polymer and fiber. As the fiber is drawn into the chamber and the bottom of the pad is formed, a portion of the polymer is added to the mix to form a layer of combined polymer and fiber. Then more pure fiber is pulled on top to give a sandwich effect.
This formation creates a pad with the absorbent polymer confined to its center, surrounded by fibrous material. Gel blockage is not a problem because the polymer is concentrated at core of pad. It also solves the problem of particle loss since all the absorbent is surrounded by fibrous material.
Many nappies that contain a wetness indicator seem to use a chemical called bromophenol blue. Bromophenol blue is a pH indicator — that is, it changes colour depending on the surrounding acidity or alkalinity. In nappies, bromophenol blue appears yellow when the nappy is dry, but the slightly alkaline pH of urine causes its colour to change to blue when the nappy is wet. Given this potential environmental impact, turning to reusable nappies might seem like a no-brainer.
However, the same study cautioned that taking into account the impacts of laundering reusable nappies, their carbon emissions impact was comparable to that of disposable nappies. This was based on a few assumptions, and the study identified that air drying instead of tumble-drying, reusing nappies with a second child, and several other factors could all bring down the impacts of reusables.
Regardless of the debate of the benefits of reusables versus disposables, disposable nappies remain the more popular of the two. To try and combat the quantities of waste sent to landfill, some companies have started to investigate how the materials in used nappies can be recycled.
One such plant near Venice in Italy aims to turn plastics from nappies into bottle caps and clothing. If enthusiasm for disposable nappies continues, perhaps this is the answer to the waste problem they pose — though it will need to be carried out at a much larger, worldwide scale.
Consider supporting Compound Interest on Patreon! And we mean all. In our research, we were not able to find credible, evidence-based studies which prove that SAP is either toxic or dangerous to humans. To the contrary, we have found some presumably tree-hugging green diaper companies who have concluded that the SAP they use is safe and non-toxic including but not limited to:. On the whole, we're left to conclude, somewhat anxiously , that the body of evidence or lack thereof suggests that SAP appears to be safe.
Perhaps as a testament to the apparent safety of SAP, our founder, Dr. Though Dr. Spurrier notes, emphatically, that if she knew then what she knows now about disposable diapers, she would have chosen cloth diapering for daytime use, and used a green disposable for overnight. However, most experts feel the SAP itself was not the cause. The use of SAP allowed the Rely tampon to absorb an entire menstrual flow, encouraging women to use the product for a prolonged period without replacement.
By , the popular Rely tampon was linked to an uptick in Toxic Shock Syndrome incidents and was recalled. As a result, the use of SAP in tampons was discontinued. Several companies have stated an intention to manufacture plant-based biodegradable SAP. Similar to the processes used for creating biodegradable trash bags, a combination of cellulose from wood or wheat, and starch from corn, potato, yams or other starch-rich plants, can be used to make a plant-based SAP which has similar absorbency to its petroleum-based cousin, but with improved biodegradability.
To our knowledge, plant-based SAP is not currently being used by any diaper manufacturer that we are aware of, but we are optimistic that it will be in the near future. Because these materials are relatively new, they have not undergone any significant testing.
However, the use of natural and sustainable materials and increased biodegradability are a virtuous combination. In disposable diapers, chlorine is used as a bleach to whiten diaper material. The problem with chlorine is that it emits small traces of known toxic chemicals called dioxins during the bleaching process.
The desire to keep baby from being exposed to dioxins is the primary motivation for using chlorine-free diapers. This type of chlorine is not the same chlorine you find in your laundry room, but a gas form of the chemical with a different chemical makeup.
Based on animal studies, dioxins have the potential to "cause reproductive and developmental problems, damage the immune system, interfere with hormones and also cause cancer.
While dioxins are only found in trace quantities in chlorine-bleached diapers, we prefer "none" to "trace" when it comes to babies, particularly newborns because their skin is so thin. That's why we advocate going with a chlorine-free diaper.
Also, upon further investigation , we aren't sure that this conviction is as useful as we once thought as dioxins are present everywhere. And while the goal would be to eliminate or limit your baby's exposure to dioxins, studies indicate it is hard to get away from dioxins with the largest culprit being the food we eat.
In fact, while trace amounts of dioxins are found in disposable diapers, the study we read indicated dioxins were also present on cloth diapers making it virtually impossible to find or choose a dioxin-free diaper option. This information makes it more difficult than we originally thought to find a truly dioxin free option no matter what the production method is.
However, before you assume it doesn't matter, the bleaching process of diapers does create dioxins that end up in the environment and eventually find their way into our food supply chain. These dioxins accumulate in our bodies and can be passed to a baby through breastmilk.
So, while it may be less important what is in the diaper, it still matters what ends up in the environment. So going chlorine free means you are doing good things for the environment, and in the long run, this translates to good things for all the babies.
Happily, going chlorine-free does not need to pinch your pocketbook. Perfume fragrances are sometimes used in disposable diapers, presumably to mask poop's distinctive stench. However, an infant's rapidly evolving organ systems are both immature and exquisitely sensitive to chemical insults. The scents found in many diapers are strong and chemical-laden, harboring unnecessary irritants with the potential to cause health issues like diaper rash and respiratory symptoms.
Equally concerning, manufacturers are not required to disclose the chemicals used in fragrances as the FDA allows them to consider their fragrances "trade secrets. Our recommendation is simple: choose a perfume-free diaper.
You don't need it, so it's not worth the risk. And, like avoiding chlorine in diapers, avoiding perfume in diapers is easy and painless. A lot of great diapers are perfume-free, and let's be honest, the fragrance doesn't mask or improve the smell of a dirty diaper.
If a diaper is stinky, you should change it, not mask it. Dyes in diapers can be found in the colored patterns on the outside of the diaper, in the leg cuff and back elastic, and in the wetness indicator.
These dyes can cause skin rash, as they may cause allergic reactions in some babies where the dye touches baby's skin. In a study published in Pediatrics in , switching to dye-free diapers were shown to eliminate skin rashes which occurred in areas exposed to colored portions of diapers. Other diaper companies, like BAMBO and Honest Diapers, use dye pigments that do not contain heavy metals, which they believe are safe and hypoallergenic. To make things even more confusing or difficult to understand or compare from one diaper to another is the terminology that each manufacturer uses.
We would like to include information on dyes in our review for choosing diapers, however, we are finding it very difficult to do so. With words like dye, disperse dye, pigments, colorants, and inks floating around depending on which diaper you are reviewing it became difficult to understand. When we tried to delve deeper to sort it out, we found even more confusing information. There seems to be no clear or consistent use of any of the words.
What one manufacturer calls a pigment, might be called a colorant by another. With no agreed-upon definitions or governing body to regulate the use of the words, it is hard to say what is in each diaper. What we found were some diapers that said dye-free had obvious prints.
When we looked at their websites for more information, we found the words pigments, inks, and colorants to describe the prints. Our take on it: we like dye-free and recommend it.
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