Nappy Materials… What Do They All Mean?

Just when you think you have your head around the different types of nappies you start hearing words like Microfibre, Bamboo, Hemp and PUL and it feels like you are back to square one.

The different types of materials used have various properties which determine how the nappy behaves. This may mean they absorb quickly, dry fast, hold a lot of liquid etc and these are the factors that determine whether the nappy is suited to your needs. Once you understand the different materials it is so much easier to work out what to use on your baby.

We will go through the main materials and then look at some case studies which exemplify how they can be used to their, and your, best advantage. Let’s start from the outside:

PUL (Poly Urethane Laminate)

This material is used as the waterproof element of most cloth nappies. On the outer of an All In One, All In Two and Pocket nappy and the entirety of a waterproof wrap or cover. PUL is an extremely useful fabric being breathable, stretchy, quick to dry, creaseproof, stainproof and crucially for nappies, waterproof.

It is made by laminating, using heat, pressure and adhesive, a thin polyester fabric to a very thin film of polyurethane. If not cared for a a reverse process happens called ‘delamination’, the fabric and polyurethane become separate and therefore no longer waterproof.

One side of the PUL is brighter and softer (being the polyester side) and the other duller and a little sticky to the touch. For this reason in most nappy systems it doesn’t touch the baby, although is harmless if it does. The common material used to line nappies and be closest to the baby’s skin is….

Fleece

Fleece is a synthetic, man-made fabric and can be derived from either virgin or recycled plastic. The fibres of polyester are woven together in such a way to create a light, breathable fabric, perfect for contact with delicate skin. This weave is the reason why fleece is also commonly found as a separate liner.

When used as a liner it picks up liquid and moves it away from the source, spreading it out and passing it through to the other side to be absorbed or evaporated. If you want to be fancy this process is called ‘Capillarity’. Due to this it obviously dries very quickly, not increasing drying time as the lining of an All In One nappy and combining with PUL in a Pocket nappy to make a very quick drying item. You will also find fleece wraps or covers used over an absorbent nappy.

Moving on to the most common absorbent materials, starting with

Microfibre

This is another synthetic material made from polyester. We learn a lot about the nature of this material from the name, the fibres of this material are tiny and there are lots of them. Larger fibres are split into tiny ones and it is the combination of the surface area created and the the space between them that causes microfibre to absorb liquid very quickly. You can feel the texture of the material when you touch it as the fibres grab at any imperfections on your skin. This and the way microfibre draws moisture into itself is the reason it is not recommended to have microfibre in direct contact with skin for prolonged periods.

Because microfibre holds liquid between it’s fibres that liquid can easily be forced back out again, like squeezing a sponge. It does, however, mean  that the liquid can begin to be squeezed out of a nappy while it is still on the baby. This is what people mean when they talk about ‘compression leaks’. the plus point to this is that microfibre dries very quickly.

Cotton

Cotton is a natural fibre and can therefore absorb liquid INSIDE it’s cells. To simplify the science, cotton has naturally occuring cellulose which has a negative charge. It attracts slightly positive water molecules, bonds together and stores the liquid inside the ‘lumen’ or empty space in the middle of each cotton fibre. This makes cotton a highly absorbent material. Because liquid is stored inside the fibres it does take longer to dry than synthetic materials.

Cotton has the same capillarity action as fleece, spreading the liquid throughout the material meaning that it can continue to absorb in the same area. The use of cotton in cloth nappies is extremely useful in preventing ‘flooding’ and consequent leaks where another material cannot absorb fast enough.

This is probably a good point to mention that with each material there are various environmental and/or ethical factors present at various points of their growth and manufacture, cotton is well known for this. While these factors may influence our choice of nappy, the conversation is complex and far reaching. A topic to return to in the future. However, it is one of the reasons that in recent times where cotton would be used it is being replaced by

Hemp

Similar to cotton in its structure and natural cellulose but with coarser, longer fibres resulting in a stronger, more absorbent and more durable fabric. Adding a hemp booster to a nappy, in particular a night nappy, can be a simple way to increase absorption speed and volume.

Although, like cotton, it gets softer the more it is used it can be rough, for this reason when we find hemp in cloth nappies it is usually a blend with cotton. The wear, wash and dry of natural material makes them less dense, increasing the spaces where liquid can be stored inside and in between the fibres. This is why we prewash and why you find excellent ‘work horse’ nappies that are years old and extremely absorbent.

Bamboo

The fabric we refer to as bamboo is properly called viscose rayon. It used to be called ‘artificial silk’ and when it comes to softness bamboo really appeals to be worn next to the skin of babies and is easily identifiable by it’s sheen. The cellulose in the bamboo is extracted and reformed into the fabric we love to use in cloth nappies. The fibres themselves, while having the same gaps and holes inside the fibres and cracks and grooves on the surface as cotton and hemp, are fine and sleeker. This is why bamboo absorbs the slowest of the commonly used materials in cloth nappies. 

As liquid is stored inside the fibres it takes longer to dry a bamboo nappy than for example a microfibre one. Bamboo rayon fibres are fine and short, it is common to find bamboo blends because the addition of cotton for example makes for a stronger fabric.

A Case Study:

An 18 month old baby who has always worn an all in one nappy with a bamboo absorbent core with no problems suddenly starts experiencing leaks within half an hour of a nappy change. 

Having checked the PUL of the nappy for any signs of delamination or holes an initial response might be to add more bamboo to increase the absorbency level. However, given the time frame of the leak it is unlikely that the child’s output has increased in volume over time but more likely that the volume of each wee is more. Toddlers can start to hold their urine for a little while increasing the pressure and volume of a single wee. A bamboo based nappy will hold a lot and wouldn’t struggle with this volume, but we know that it absorbs slowly so the liquid will run to any escape points such as the seams of the nappy before the bamboo has had time to absorb all the liquid. The best solution here would be to add a cotton or hemp booster inside the nappy. Microfibre may work on a younger baby that is less mobile and likely to compress the nappy. By adding it inside the nappy the faster absorbing material can quickly manage the liquid giving time for it to  to spread throughout the absorbent parts of the nappy and be stored. This means that there is still capacity for more output so an immediate change isn’t needed.

A Case Study

A 3 month old baby has been wearing a 2 part, microfibre based nappy system which until now has been excellent at containing liquid poo and the frequent small wees she has been having. They have been changing regularly day and night. Now the little one is sleeping longer at night they require something more absorbent to last longer.

Two Part nappies are excellent and quite often the best solution over night. There is twice the protection at the leg and waist against leaks. These parents will want to consider a bamboo nappy for maximum over night capacity. They may want to line it with a fleece liner to help keep the bottom feeling dry by wicking the moisture away. Over the nappy they can continue to use their PUL wrap. Over time depending on the child they may want to add additional boosting of more bamboo or hemp either inside the nappy or between nappy and wrap.

Cloth Nappies should be simple to use, by understanding the components of them we have more chance of selecting an appropriate nappy and much more chance of successful  and sustainable use. Whether it’s one a day or full time use you are aiming for it all makes a difference to you, to baby and to the environment.

For advice on cloth nappies please email: nappies@yesbebe.co.uk

Sources: www.sciencedirect.com, www.madehow.com, www.theartofcleanliness.com, www.sciencing.com, www.oecotexfiles-wordpress.com, www.researchgate.net, www.textileinsight.blogspot.com, www.towelswell.com

 

3 thoughts on “Nappy Materials… What Do They All Mean?”

  1. What a great informative blog! This was one of the questions I asked last cloth clinic so thanks for clearing all of this up for me!

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