Patch Science: Threadlock vs. Airlock

Trail repairs come in two flavors: woven fabric (packs, jackets, tents, stuff sacks) and TPU film (sleeping pads, water bladders, dry bag liners). The substrates behave differently, so the patches do too. Threadlock handles fabric. Airlock handles TPU. Using the wrong one is the single biggest reason field patches peel.

Which patch for what

Why two patches: A woven face flexes with woven fabric and won't peel at the edges. TPU bonds to TPU at the molecular level — like welds to like. Cross-using them works in a pinch but won't last.

Surface prep — this is what actually decides if it holds

Adhesion failure is almost always contamination, not the adhesive. If you can still smell sunscreen on the fabric, the patch will fail. Clean first.

Application

If you cut a patch smaller for a tiny puncture, round the corners. Sharp corners are where peels start.

Bigger or trickier damage

• Long tears: multiple patches with ~5 mm overlap, shingled so any water runs over the seam, not into it.
• Jagged tears in fabric: stitch first to take the load, then cover stitches with Threadlock.
• High-shear spots (corners, seams, strap mounts): oversize the patch and burnish hard. On packs, patch both sides of the fabric.

When patches won't work

FAQ

Is Airlock really clear? Yes. On translucent pads and bladders it nearly disappears.

Do I need heat or a lighter? No. These are pressure-sensitive — pressure and time activate them.

How long do unused patches last in storage? Years, if kept sealed at room temperature and out of direct sun. Don't leave them in a hot car all summer.

Can I patch a wet pad in the field? Dry the spot first — bandana, body heat, a few minutes under a tarp. A patch applied to wet TPU will not hold.

Will these hold on a pad I'll sleep on tonight? Yes. Most of the bond strength is there as soon as you finish burnishing. Full cure happens overnight.

Threadlock for fabric. Airlock for TPU.
Clean the surface, peel-place-roll, burnish for 20 seconds, done.