The Fabrics

Modern cloth nappies are made of various types of fabrics. The outer is normally a waterproof or water repellent fabric and the inside has the fabric that absorbs.
Waterproof vs Water repellent
Waterproof fabric examples are TPU (thermoplastic polyurethane) and PUL (polyurethane laminate).
PUL is a chemical that is laminated onto fabrics (such as polyester or cotton) which then forms a flexible waterproof layer. PUL is said to be laminated using solvents in a chemical bonding process.
Benefits to using cloth nappies with a PUL outer layer are:
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Durability - stands up to many washes
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Waterproof material to keep the wetness inside the nappy
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Flexibility so it can easily be applied to fabrics
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Comfortable for the baby
Potential drawbacks to using PUL:
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Non-biodegradable (as it is a form of plastic)
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It is synthetic (man made) and some babies may have a sensitivity to synthetic materials
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Not as breathable as other all natural fibres like wool or fleece soakers (but more breathable than disposable nappies)
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Can delaminate if exposed to extremely hot temperatures
TPU has a different manufacturing and application process to PUL. TPU is bonded to cotton or polyester using a heat bonding lamination process which is kinder to the environment. During the lamination process, solvents are not used, and thus TPU is said to be exposed to fewer harmful chemicals.
Benefits to using cloth diapers with a TPU outer layer are:
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Said to be more environmentally friendly (biodegradable)
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Has a softer feel to it
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More flexible and less stiff than PUL
Potential drawbacks to using TPU:
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Said to be less durable (than PUL)
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More prone to delamination and cracks with higher temperatures
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It is synthetic (man made) and some babies may have a sensitivity to synthetic materials
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Not as breathable as other all natural fiber alternatives like wool and fleece (but more breathable than disposable nappies)
Water repellent/resistant fabrics would be polyester fleece or lanolised wool.
Microfleece lets moisture through and is good for a stay-dry lining inside a pocket nappy or for liners. Anti-pill repels water and is good for use as a water repellent layer in hybrids.
Wool covers (soakers) can be used as covers for overnight use too. One needs to lanolise them using lanolin (sheep wool fat). Wool soakers are normally knitted or crocheted using 100% pure merino wool. No buts. 100% pure merino wool. Sheep’s wool.
Water repellent/resistant fabrics are great for overnight use for babies who tend to need a little bit more breathability for overnight use


Absorption
One of the aspects that sets nappy types apart are the layers used for absorbancy. Options are synthetic fabrics and/or natural fibres. An example of a synthetic fabric is microfibre (polyester). Natural fibre examples are cotton, hemp, bamboo or a mixture of them.
Microfibre needs pressure to absorb and it absorbs fast. A con is that it could lead to compression leaks. Microfibre inserts are similar to sponges. You press a wet sponge, the liquids will run out. Keep in mind that Microfibre can never go directly against baby's skin (it absorbs too fast and could dry out your baby's skin). Always use them inside a pocket or cover it with a liner to protect baby's skin. Microfibre inserts dry quickly. The pocket lining (microsuede (polyester)) of pocket nappies are also a synthetic fabric but has a stay dry feel for baby.
Natural fibres contain liquids well and are trim options for inserts. Natural fibres can go against baby's skin. Note that baby can feel wetness with natural fibres (it doesn't have a stay-dry feel). For most babies this is not a problem at all, natural fibres can feel a lot more comfortable than synthetic fibres. Natural fibres are recommended for overnight use because it contains liquids better than microfibre. Natural fibres tend to become hard when dried in the sun. A quick rub between your hands will soften them. You could also throw them into your tumble drier for ten minutes to soften them.
Organic Cotton
Organic cotton is a natural fibre that stays soft. One drawback of organic cotton is that it stains easier than other natural fibres. For that reason we recommend that you treat stains immediately if using organic cotton or dry in the sun (the sun is magical with stains! A natural bleaching and will get rid of stains)
Bamboo
Bamboo is a natural fibre that is very trim. A con of bamboo is that it could deteriorate faster than synthetic fabrics. It's a combination of how bamboo fabric is made (as bamboo need to first be dissolved then extruded to turn into threads and then knit/woven into fabric), the quality and durability of the fabric (not all bamboo are the same), stress and friction it is subjected to, and wear and tear etc. all play a role
Hemp
Hemp has an excellent trimness vs absorbent ratio, so it can hold a lot of moisture for it's trimness, hence being especially popular for night time cloth. Hemp do tend to get stiff when line dried therefore requires you to rub or tumble dry them to soften up. Hemp absorbs slower than other fabrics. That’s why some pocket nappies have 1 microfibre and 1 hemp insert. A great combination – microfibre that absorbs fast, paired with hemp that absorbs slowly but contains liquids well. So the hemp inserts catches the “overflow” from the microfibre insert. Hemp/cotton blend inserts work excellent for this reason as well, the cotton will absorb quickly and the hemp will hold on to the moisture
Cotton
All “knits” are stretchy. So whatever fabric is in “knit” form would be stretchy.
Cotton like flannel is a more affordable alternative in natural fibres with all the benefits: trim, holds moisture and is very absorbent
It is overwhelming to choose which types of fabric to use. At first, you will need to establish whether your little one is sensitive to any of the fabrics used (This is rare). Keep in mind though that some babies might develop a sensitivity at a later stage, a previous sensitivity can also disappear as baby gets older. They like to keep us on our toes, don’t they? Sensitivities are easily and cheaply handled by using liners (stay-dry if baby reacts to wetness or cotton if baby reacts to synthetic fabrics in a cloth nappy).
*TPU/PUL source:
http://myclothdiaperstash.blogspot.co.za/2012/09/pul-vs- tpu-delaminating-differences.html
