What Makes The Outside Of A Cloth Diaper Waterproof

What makes the outside of a cloth diaper waterproof?

GOOD QUESTION. The outer material of a diaper cover, pocket diaper, all-in-two or all-in-one diaper is made from PUL or TPU. Most brands today use TPU (thermoplastic polyurethane) which is a thin film of polyurethane laminated onto a polyester base fabric. TPU uses high heat to bond the film to the base fabric. Older style PUL (polyurethane laminate) used heat, pressure and other chemical solvents to bond the film to the fabric. Sometimes people in the cloth diapering world use TPU and PUL interchangeably to mean 'the waterproof outer fabric', but technically they are slightly different even if the resulting fabrics are both water resistant.

TPU is special because while it is water-resistant, it also allows airflow (unlike a plastic film) and air circulation decreases the risk of diaper rash for baby's skin even in warmer climates. Because TPU is also washable, durable, and lightweight it makes an excellent fabric for manufacturing cloth diapers for babies. It's also used for accessories like wet bags for storing soiled diapers or cloth menstrual pads before washing, for baby diaper changing pads, diaper pail liners and the like. It can be washed and reused many times without the color bleeding or fading over time.