Most modern cloth nappies and covers use a special fabric to make them waterproof. The fabric is called PUL (Polyurethane Laminate) or TPU (Thermoplastic Polyurethane) and basically refers to a fabric (either polyester or cotton) with a thin polyurethane layer bonded to it in a high heat or chemical process.
The waterproof film is usually adhered to the fabric in a small dot pattern, and the bonded fabric should look and respond as a single layer of fabric.
When these two layers come apart it is referred to a 'delamination'. The end result of delamination is a nappy that is no longer waterproof - a seriously sucky thing.
What causes delamination?
Delamination can be caused by several things, though in the usual scheme of things a nappy should only delaminate after it has been well used and is at the end of its lifespan. Over the lifetime of a reusable nappy, the PUL (like all other components) will deteriorate. Much like elastic loses its pliability and snap, PUL can become brittle and crack, or the adhesion can lose its bond, with 'blisters' forming where the film separates from the fabric. Quality plays a part here - the thickness of the polyurethane film and quality of the adhesion will impact the longevity of the PUL - as well as the wear and tear. A nappy that is worn and washed every day can be expected to break down faster than one that is washed a couple of times a week. Remember that any nappy that's been used regularly for two or three years has experienced more wear and tear than almost any other item of clothing. See our article on how long you should expect your cloth nappies to last.
Some things can speed up the process, though, and cause delamination of a nappy before it might be expected.
- High heat: This is the most common cause apart from wear and tear. Washing in water hotter than recommended by the manufacturer and drying on high heat in a dryer will cause the PUL to break down faster, especially if done on a regular basis. Remember too, that the Australian sun can get really hot, so don't leave your nappies baking out in the sun for hours at a time during summer (it will make your elastic brittle, and damage fabric fibres as well as affect the waterproofing).
- Laundry additives: Bleach will damage the waterproofing in your nappies, causing it to thin and crack. Vinegar is another culprit.
- Soaking: While soaking in bleaches etc will cause problems with PUL, some manufacturers also recommend against soaking their nappies in plain water regularly as it can eventually lead to delamination.
- How long your nappies sit in the pail before being washed and if your child has strong, acidic 'toxic' wee can be contributing factors. Damage caused by a ring (especially in the case of pocket nappies where your hand comes into contact with the PUL) can cause partial delamination as it scratches and breaks the PUL.
- Manufacturing fault: It sometimes happens there is a bad batch of PUL fabric manufactured in which the adhesion of the film and fabric isn't as it should be. Or sometimes fabric from the end of the roll (where the lamination isn't complete) is inadvertently used in the manufacture of a nappy. This sort of delamination generally becomes obvious within a few months (or sooner) of the nappy being used.
How do I know if my nappy has delaminted?
If you have a pocket nappy, turning the nappy inside out will usually reveal the inner side of the PUL. If the PUL has become brittle and cracked, you will be able to see the outer fabric exposed through the cracks, especially when you stretch the fabric slightly. You may be able to see larger tears or holes.
If the film has started to pull away from the backing fabric, then you will see:
- wrinkles - especially obvious when you run your finger along the film (note this is different to the normal texturing found on some PUL),
- small (or large) blistering, and possible tearing or,
- complete separation of the two layers.
Sometimes a delaminated nappy will make a rustling sound when you rub it.
Can I fix delamination?
No.
Seriously, you can't. There are suggestions on the internet that putting your PUL covers/shells in a hot dryer can help reseal cracked or separated PUL. It doesn't work, and in fact will most likely make it worse.
Courtney at the Diaper Wrecker has entertainingly tried various methods for repairing a delaminated nappy with no positive results.
Can I keep using my delaminated nappy?
So long at there are no holes or cracks in the membrane, then the integrity of the waterproofing remains intact and you can continue to use the nappy (some people can use them for months). However, it is easy to tear a hole in the film with your fingernails or a ring while stuffing a nappy, and agitation in the washing machine can cause the film to tear at the seams along the stitching lines. Delamination usually indicates that a nappy is reaching the end of its usable life, and once you start getting leaks, that's it.
If the rest of the nappy is in good order, another option can be to pop another cover over the top as your waterproof layer.
Delaminated pocket nappies make good swim nappies, since they don't need to be absorbent (remove the inserts), but you'll want to make sure the elastic is in good order to provide containment around the legs.
Here's a video showing close ups of nappies in various stages of delamination: