Disposable diapers are made from everyday materials with a long history of safe use in various standard consumer products. It is primarily made of cellulose, polypropylene, polyethylene, a super absorbent polymer, and minor amounts of tapes, elastics, and adhesive materials. Advances in these materials have made diapers lighter, thinner, and more effective. The most recent advances in disposable diapers have been in the area of reducing their environmental impact by using renewable resources and creating biodegradable brands that can be disposed of with your regular trash.
Disposable diapers have been around for a long time, but modern disposable diapers have undergone several improvements in materials and construction to improve their performance, fit, and skin comfort. In recent years, these advances have also reduced the environmental impact of disposable diapers.
Parts of a Diaper
A diaper is made up of two primary parts: the diaper core and chassis.
- Diaper core. The core is the middle of the diaper, where urine and liquid feces are absorbed and stored. It’s usually made of a soft material that draws moisture away from the baby’s skin, preventing rashes and other infections.
- Diaper chassis. The chassis is the part of the diaper that holds everything together, attaches it to your baby, and creates a proper fit around their legs. It also helps you determine if your baby needs new diapers at any point in time.
The diaper core, also known as the absorbent core or the absorbent media, is made up of a combination of polypropylene, cellulose, and superabsorbent polymer. It’s designed to absorb liquid and trap it within the diaper. This keeps your baby dry, comfortable, and healthy while they’re wearing it.
- Top sheet. Top sheets are the part of a diaper that comes into contact with the baby’s skin. They have been specially designed to be soft and dry, while also transferring fluids quickly to the core of the diaper. This helps keep the baby’s skin hydrated and reduces irritation. Some top sheets include moisturizers, such as those found in diaper skin-care products, which can protect the baby’s skin from overhydration and reduce irritation.
- Distribution Layer. In the 1980s, researchers developed superabsorbent polymers that can absorb many times their weight in fluids. As a result, children’s skin health has improved because these polymers lock moisture away so it cannot irritate the skin. As a result, the severity and frequency of diaper rash have declined dramatically. In addition, as technology has improved, less and less cellulose has been needed. This allows significant diaper weight and volume reductions, resulting in a reduced environmental impact.
- Absorbent Core. The absorbent core is the innermost layer of the diaper, and it typically consists of a blend of cellulose fluff pulp and polyacrylate granules. The cellulose portion quickly absorbs and transfers urine to the superabsorbent polyacrylate material, where it is trapped. This keeps the baby’s skin dry, even if they sit on a full diaper. The superabsorbent material can hold up to 10 times its weight in liquid, which means it can soak up to 10 times its weight in fluid throughout the day!
The chassis of a diaper is where the back sheet and additional features that ensure the diaper fits well are joined together. These features include stretch side panels, fastening systems, tapes, and leg cuffs.
- The back sheet is the water-resistant outer layer of the diaper, preventing liquids to penetrate the diaper and spreading on the baby’s clothes or in the surrounding environment. The polyethylene backrest can be made with a structure that allows water vapor and air (but not liquids) to pass through, reducing moisture and keeping skin drier. The back sheet is made of polyethylene, which has many advantages over natural materials such as cotton. It’s lightweight and breathable, which means it won’t weigh down your baby or cause them to feel confined. It’s also extremely durable—so much so that it can withstand repeated washing without losing its shape or elasticity.
- Fit and Comfort Features. Diapers are designed to fit snugly against the baby’s body. The three most important parts of a diaper for this purpose are the stretch side panels, the fastening system, and the elastics on either side of the diaper. The stretch side panels should be wide enough for the diaper to form a good seal around the baby’s torso, but not so wide that they will cause discomfort or chafing. The fastening system should allow for easy adjustment so that it fits snugly around the waist without being too tight. The elastics on either side of the diaper should be large enough to prevent leakage but small enough that they do not cut into babies’ skin or cause irritation when they pull them up.
Raw Materials Used in Diapers
|Polypropylene (PP)||Primarily used for the top sheet, the part of the diaper next to the baby’s skin, tapes, and fastening system.|
|Polyethylene (PE)||Mainly used for back sheets, outer covers, tapes, and fastening systems.|
|Cellulose Fluff Pulp||Absorbent core and central fabric.|
|Superabsorbent Polymer||Absorbent core.|
|Elastics||Along the leg opening and waist to improve fit.
|Adhesives||Throughout the diaper to bond various other materials together.|
- Polypropylene (PP).PP is a non-woven fabric that gives the diaper a comfortable shape and helps prevent leaks. PP fabric is used for the top sheet which is the layer that sits on the skin. PP is a hydrophobic material that lets liquid in, but not back out (helps keep babies’ skin dry).
- Polyethylene (PE). Polypropylene is widely used in diapers and sanitary products owing to its higher water absorption capacity. In addition, PP nonwoven fabric has been increasingly gaining acceptance due to its superior physical qualities, such as lightweight, reusability, toughness, and flexibility, compared to other nonwoven materials.
- Cellulose Fluff Pulp. It is cellulose used as the diaper’s core to absorb liquids. It gives an excellent absorbing capacity to the diaper. In addition, the pulp has qualities such as a high ratio of fibers to weight, lower coarseness, and shorter fiber length.
- Superabsorbent Polymer. Superabsorbent polymers are primarily used as water absorbents and aqueous solutions for diapers, and similar applications. These superabsorbent polymers can absorb several tens to several hundred times their weight in fluids. For example, 1 gram of superabsorbent material in a diaper typically absorbs at least 35g of urine. By contrast, 1 gram of pulp absorbs approximately 10g of urine.
- Elastics are a crucial component of making an effective diaper. Without them, you don’t have the adjustability or containment needed.
- Adhesives help prevent leaks by keeping the fluffy, absorbent fibers and superabsorbent powder in the middle (core) of the traditional diaper, pull-on pant diaper, or pad. Adhesives are also used to hold the many strands of elastic around the diaper or pants’ legs and waist areas.
How Disposable Diapers are Made?
Forming the Absorbent Pad
Forming a pad is an important step in the process of creating an absorbent diaper.
- The absorbent pad is made by drawing a long conveyer belt through a forming chamber filled with pressurized nozzles. The underside of the conveyor belt punctures and a vacuum pulls the fibers down to form a flat pad.
- An absorbent material is applied onto the pad’s top surface after it has been formed. This approach sometimes results in blockage where moisture is trapped in the outer layer and does not spread to the center. This will hold water against the skin and cause discomfort.
- Different sprayers apply different layers of polymer and fiber to the pad. After the fiber has been drawn towards the center and the bottom pad has formed, the polymer is added to the mixture to form a combined layer of polymer and fiber. This creates an absorbent polymer pad with fibrous materials surrounding it at the center.
- The pad then advances along the conveyor belt to a leveling roller near the forming chamber exit. The leveling roller removes some of the fiber at the top of the pad to ensure uniform thickness. The pad then continues along the conveyor belt.
Forming the Nonwoven Fabric
- After forming the nonwoven fabric, manufacturers can use guiding web systems to make their products quickly and efficiently. Plastic resin from the meltdown process forms nonwoven sheets, and the guiding system’s wide web rolls cut the fabric to the appropriate width. This process occurs for both the top and bottom sheets. It’s important to note that these sheets form in a different location than pads, so this step doesn’t necessarily occur after pad formation.
- Stretched rubber bands attach to the backing sheet with adhesive. These bands contract and come together to ensure a snug fit and prevent leaks.
- The final step in the diaper manufacturing process is cutting and folding. At this stage, there are three main diaper parts: the absorbent pad, the top sheet, and the bottom sheet. The absorbent pad and bottom sheet go through a conveyor belt to align them in place. The top sheet is pushed into place and the filled parts are glued, heated or ultrasonically welded. These come out as a long strip or roll.
- The long roll is cut into individual diapers, then folded and packaged for shipping.