You might have heard the terms PUL or TPU referring to the water-resistant outer fabric found on some styles of cloth diapers, but what's the difference and why does it matter?
PUL stands for Polyurethane Laminate, it's polyester fabric laminated with a plastic-like film called TPU (Thermoplastic Polyurethane) to make it water-resistant.
Polyester fabric + TPU film = PUL water-resistant fabric
PUL is the laminated fabric, TPU is the plastic-like film used to laminate it. TPU is NOT a fabric. TPU is actually a part of PUL.
Some diaper manufacturers refer to their diapers' water resistant outer layer as being TPU which just specifies what type of laminating they used to make the PUL (thermal bonding rather than chemical bonding). But, it's not incorrect to say the outer layer of any cloth diaper is PUL. Make sense?
Now, to be specific, there are 2 ways to make PUL:
1) The old way used chemical solvents to bond the plastic TPU film to the polyester fabric. It wasn't the most environmentally friendly, but did result in a very durable PUL fabric that was very useful in the medical industry as it could withstand boiling and routine autoclaving (sterilizing) at very high temperatures while being water resistant. Fabrite brand PUL was the most infamous for being made in this way and was often used for cloth diapers prior to 2010.
2) In 2010 AKAS Textiles & Laminations developed a PUL that was thermally laminated with TPU. This new technique got rid of the need for chemical solvents by bonding the TPU to the polyester using only heat and pressure. PUL that comes from thermally bonding in this way results in a fabric that is softer, more pliable, and more environmentally friendly. Without the need for chemical solvents to create the PUL, there is no discharge of VOCs (Volatile Organic Chemicals), no solid waste byproducts and no fumes released into the air.
Currently, almost every brand of major cloth diaper now uses thermally-bonded PUL rather than the old-style chemically bonded PUL. It's durable, long-lasting, pliable and functional. Plus, more friendly to our environment.