PUL, or Polyurethane Laminate, is the waterproof layer of material often used in cloth diapers.  Pockets, All-in-Ones, All-in-Twos and Diaper Covers most often use this on the outer layer of the diaper as a more breathable alternative to the old Rubber and Plastic pants of the previous generation of cloth diapers.

Example of laminate inside and polyester outside (at top) of this Flip Cover

So what exactly is PUL? When you look at many diaper covers you can see that there is a “wipeable” side which is inside, and a cloth like outside, which is usually polyester or cotton.  The laminate side has been fused to the cotton or polyester side using heat or a chemical process.  Usually this process is permanent and the two layers stay together for the long haul.  However, certain chemicals and other mistreatment of this material can cause the laminate to separate from the fabric outer, in which case the diaper will begin to have leaks through those areas.  It will bubble up and appear like a peeling sunburn.

Cotton or Polyester? Pretty much any diaper you have seen uses polyester as the soft fabric side.  While cotton offers many options for cute prints, these wick more.  The bigger brands can afford to commission large quantities of proprietary prints in polyester PUL.  The reason you don’t see many prints is for that reason, they are expensive and require large orders.  Not to mention they need to be designed.  Remember, the fabric has to look good rightside up and upside down.  A lot of diaper makers who really want to have fun prints choose to use a regular cotton knit sewn over a hidden layer of PUL.  Some are successful in this (GEN-Y Covers have NEVER leaked or wicked for me) but other diapers end up with horrible wicking (moisture from the inside of the diaper migrating to the cotton, usually around the legs.)

1 Mil or 2 Mil? PUL has either a 1 mil or 2 mil thick layer of the laminate backing.  It is up for debate whether or not 1 or 2 mil is better.  1 mil certainly feels thinner, but 2 mil has an extra layer of protection.  It could be argued that 1 mil will potentially wear down quicker over time.  You could also argue that 1 mil would be more breathable since there is less waterproof laminate for air to come through.  I have not seen conclusive evidence of either.  Unless you are making your own diapers and buying PUL, most consumers don’t even realize there are different types of PUL being used.  If you are buying your own PUL, 1 mil is easier to find and less expensive.

Examples? Bummis covers are made with 2 mil PUL.  bumGenius! products use 1 mil, for a comparison.  The Bummis covers definitely feel thicker.  Understandably, some people do not wish to use 2 mil because it is harder to work with and sew.

Some of the larger brands commission their own PUL with distinctive brand specific colors (think Bum Genius) and patterns, (think Mother-Ease).  bumGenius! have stated that they do not use a chemical solvent process, and they also believe their PUL is made in an environmentally friendly way.

Many other brands and WAHM’s have been using a brand of PUL called Fabrite which I recently learned is considered the best for diaper making.  Unfortunately this brand stopped production.  Unbeknownst to consumers, diaper makers are scrambling to find a comparable alternative, of which there aren’t many.  Fabrite used a solvent process described as”The PU film and knit are coated with a solvent based adhesive that slightly liquefies the surface of the PU film and knit, then pressure is used to fuse the fabric together.”  source: Wazoodle

After speaking to others I have learned not everyone thought Fabrite was the best.  Many used to use it and later went with a heat solvent PUL.  Nifty Nappy prefers the heat solvent PUL also.

There is another term floating around regarding PUL and this is TPU.  TPU stands for Thermoplastic Polyurethane.  This is where it gets hairy.  According to Rumparooz, who uses TPU, they regard it in another category altogether.  Taken from Rumparooz’s Website:

In 2008 Kanga Care started using a biodegradable TPU waterproof material. Biodegradable TPU is solvent-free. Biodegradable TPU is a polyester fabric that has been laminated with a thermoplastic polyurethane using a heat bonding process. This process is low in toxicity and is better for the natural environment. Both the TPU laminate and the polyester fabric the laminate is applied to are biodegradable.  When composted they will biodegrade in 4-5 years.

However, the fabric distrubutors Wazoodle, who issued a highly informative breakdown of the different PUL’s, say:

TPU is the technical name for polyurethane film used to make all PUL, new and old.  A few vendors heard TPU for the first time and thought it would help them make their items sound different — just marketing tricks!

So if TPU is better for the environment why aren’t more diaper manufacturer’s using it?

It could just be that they are, and the TPU is just a fancy name for the heat solvent version of PUL that many manufacturers use.  It is all very confusing for someone who does not make diapers!

Bottom line?

It is near impossible to know exactly which PUL a diaper is using unless you ask.  Some makers are very forthcoming, others believe their proprietary PUL recipe should be kept secret.  I found both sides when looking into this post.  You will also see that some diapers source PUL from China, but other brands are still careful to use PUL made in the US.  I still believe PUL has made the cloth diapering revolution possible. I love my Pockets and couldn’t live without them.  Cloth diapers are better than disposables any day, no matter how the PUL was made, but it isn’t something you should keep your head in the sand about either.

What is I don’t want to use PUL but want to use cloth diapers? If you are concerned that PUL production is bad for the environment there are certainly other options.  Wool and fleece work just as well at keeping leaks at bay.  While it isn’t practical to expect every cloth diaper user to use these materials, if you really want organic and conscientiously produced diapers wool and fleece might be what you need.

For responsibly made wool I would recommend: Sustainable Babyish, Better for Babies (Little Beetle), and the WAHM’s out there who upcycle wool into soakers or hand knit them (Hyena Cart and Etsy will yield results).

If you prefer fleece (easier to care for overall and less expensive) I suggest Lollidoo, who use recycled plastic bottles to make their fleece!  Also, there are WAHM’s who upcycle fleece to make soakers as well.

Special thanks to the cooperative diaper companies I contacted: bumGenius!, Bummis, and Nifty Nappy, who were very helpful in answering my questions.

Images: Flip- clothdiapers.blogspot.com, PUL- www.zjgxdiaper.com