What is PUL Fabric?

You know that moment when you’re layering up a diaper cover or a wet bag, and you realize the outer fabric needs to be waterproof but not feel like a trash bag? That’s where PUL steps in—and honestly, once you’ve sewn with it, you wonder how you ever managed without it.

What is polyurethane fabric?

PUL fabric—short for Polyurethane Laminate—isn’t just another waterproof textile. It’s a performance hybrid: a tightly woven polyester face fabric bonded to a thin, flexible polyurethane film. The result? A material that blocks liquids but still lets air move through, which is rare in waterproofs. Most waterproof fabrics trap heat like a sauna, but PUL manages moisture and breathability in a way that makes it ideal for skin-adjacent or frequently washed items.

The lamination process is what sets it apart from coated fabrics. Instead of painting on a chemical layer (like PU coating), the polyurethane is fused as a continuous film under heat and pressure. This creates a more durable, consistent barrier that won’t crack or peel as easily over time. I’ve tested PUL after 50+ washes—still waterproof, still soft. Try that with a vinyl-coated fabric and you’ll get stiff, delaminating disaster.

What makes PUL fabric unique?

It’s the balance. Most waterproof materials sacrifice one thing for another: waterproofness vs. drape, durability vs. breathability. PUL actually holds the line on both sides.

The laminate advantage

That 1-mil polyurethane film (about the thickness of a sandwich bag) is key. It’s thin enough to stay flexible, but dense enough to stop liquid penetration. Unlike TPU laminates, which can yellow or stiffen under UV exposure, PUL holds up better in regular indoor use—think diaper covers, bed pads, or tote linings.

And because it’s bonded to knit polyester (usually 95% polyester / 5% spandex for 2-way stretch), it has a soft hand and gentle give. That stretch matters when you’re sewing snug cuffs or contoured waistbands. It moves with the body, not against it.

How does PUL fabric work?

When liquid hits PUL, it doesn’t absorb—it beads. That’s the hydrophobic nature of polyurethane in action. The water rolls off or sits on the surface until wicked away by an absorbent layer underneath (like fleece or cotton in a diaper). But here’s the subtle part: while it blocks liquid, it allows vapor to pass. That’s breathability, not just porosity.

This is why PUL outperforms vinyl or oilcloth in wearables. It reduces clamminess. You don’t get that “sweaty plastic” feeling because moisture vapor from skin can escape. It’s not as breathable as cotton, sure—but for a waterproof layer, it’s surprisingly airy.

Now, here’s a pro tip: avoid ironing directly on PUL. The heat can melt or bubble the film. If you must press a seam, use a pressing cloth and low heat—like 275°F max. I keep a Teflon sheet on my ironing board just for laminates.

Needle and stitch settings

• Needle: Size 75/11 Microtex or Universal
• Stitch length: 2.5–3.0 mm
• Presser foot: Use a Teflon or walking foot to prevent drag

PUL can creep under the foot if you’re not careful. A walking foot helps feed both layers evenly, especially when sewing PUL to thick fleece or PUL to PUL.

Applications of PUL fabric

PUL’s sweet spot is anywhere you need quiet waterproofing—no crinkling, no stiffness, but full liquid resistance.

Reusable diapers

This is where PUL shines. As the outer shell, it keeps moisture in while allowing airflow. I’ve seen parents swear by PUL over TPU here because it’s quieter and softer against baby’s skin. The knit backing conforms to movement, reducing gaps at the legs.

But not all diaper PUL is created equal. Look for at least 65 gsm (grams per square meter) for durability. Lighter weights might leak under pressure or wear thin after repeated washing.

Mattress protectors

Hospital-grade or home use, PUL creates a silent, seamless barrier. No one wants to hear crinkling every time they shift in bed. Compared to vinyl-backed protectors, PUL is whisper-quiet and more breathable—critical for overnight comfort.

One thing I’ve learned: double-stitch the seams on mattress covers. PUL doesn’t fray, but the stress points (corners, edges) can delaminate over time if not reinforced. A second row of stitching 1/8″ in from the first adds longevity.

Bags and totes

Wet bags, swim totes, diaper backpacks—PUL lines them all. It’s water-resistant on the outside and easy to wipe clean inside. I once made a wet bag for a client who used it daily for soiled cloth diapers. After six months of boiling washes, it still looked new.

But here’s a real-world quirk: PUL doesn’t handle sharp objects well. A stray safety pin or zipper pull can nick the film. Once breached, the waterproofing fails at that spot. So I always recommend bag interiors with a fabric liner over the PUL, especially if storing pointy items.

Medical products

Surgical gowns, bed pads, wound drapes—PUL shows up in medical textiles because it’s fluid-resistant and latex-free. It’s not sterile on its own, but it can be sterilized. Hospitals often prefer it over PVC because it’s lighter and less plasticky.

One hospital supplier I worked with switched from vinyl to PUL for pediatric bed pads. Nurses reported fewer skin rashes and better patient comfort. The material still holds up to disinfectant wipes and frequent laundering.

Advantages of using PUL fabric

Let’s cut through the hype. PUL isn’t magic, but it’s the most practical waterproof fabric for sewists who want performance without compromise.

• Waterproof: Yes, truly. Spills bead up, not soak through.
• Breathable: Allows vapor transmission—critical for wearables.
• Durable: Withstands 100+ washes if cared for properly.
• Easy to clean: Wipe with a damp cloth or toss in the machine (cold or warm, never hot).
• Flexible: Drapes like a soft knit, not a stiff tarp.
• Eco-smart: Enables reusable alternatives to disposables, cutting down on waste.

But it’s not perfect. PUL can delaminate if dried on high heat or folded sharply under pressure. And it degrades under prolonged UV exposure—so not ideal for outdoor gear left in the sun.

Case Study: The Diaper Cover Redesign

A small cloth diaper brand came to me after their first batch of PUL covers started peeling at the leg elastics. They’d used a 1-mil PUL but sewed it with a standard stitch and no seam sealing.

We tested three fixes:

1. Double-stitched seams – helped, but didn’t stop wicking at needle holes
2. Iron-on seam tape – too stiff, cracked after wash
3. Liquid seam sealant (nylon-based) – applied after sewing, cured in 24 hrs. Worked perfectly.

The trade-off? Added production time. But the return rate dropped from 12% to under 2%. Sometimes the “right” fix isn’t the fastest one.

Micro-note:

I once washed a PUL-lined tote on hot, just to see what would happen. The film survived, but the polyester face shrank slightly—enough to cause rippling. Lesson learned: always wash PUL in cold.

Micro-note:

Not all PUL feels the same. Some mills use a tricot knit base; others use a mesh. Tricot is softer, but mesh breathes better. Depends on your end use.

Final Thought

PUL fabric works best when you respect its limits. It’s not for high-heat projects or outdoor tarps. But for everyday waterproofing that needs to move, breathe, and last? It’s still the gold standard. And if you’re sourcing in bulk, stick with mills that specify 1-mil lamination and US-made film—like the supplier I use for Pura Fabric’s inventory. The consistency makes a difference when you’re cutting hundreds of diaper shells.