Materials · Bag Encyclopedia
PVC Tarpaulin for Waterproof Bags
Sewn bags leak at the seams because every needle hole is a water entry point. Welded PVC tarpaulin bags are watertight because the seams have no holes — they're molecularly fused. Here's how the process works, which IPX rating you can honestly claim, and where tarpaulin bags win.
The PVC tarpaulin fabric
PVC tarpaulin is a polyester scrim (grid of woven yarns) sandwiched between two layers of PVC coating. The scrim gives it tear strength; the PVC gives it waterproofness and weldability. Weight ranges from 500 g/m² for light dry bags up to 900 g/m² for industrial totes and truck-cover-grade bags.
- 500 g/m² — dry bags, roll-top duffels.
- 650 g/m² — fishing bags, kayak deck bags, wet gear duffels.
- 900 g/m² — industrial totes, truck bed bags, marine gear bags.
RF welding — how the seam is fused
An RF (radio frequency) welder generates a high-frequency electromagnetic field at 27.12 MHz. When two layers of PVC pass between the electrodes, the field excites the PVC molecules, generating heat inside the material itself. Pressure from the electrode fuses the softened PVC into a single homogeneous layer along the seam line.
- Weld width — 10–15 mm typical.
- Weld strength — 80–95% of parent fabric tear strength.
- Cycle time — 3–8 seconds per weld pass.
- Alternative — hot-air welding for cleaner PVC-free specs; slower but VOC-free.
IPX rating claims — what's honest
| Rating | Definition | Construction needed |
|---|---|---|
| IPX3 | Spraying water | Coated fabric + taped seams |
| IPX4 | Splashing water | Best sewn + seam-taped |
| IPX5 | Water jets | RF welded seams + zip cover flap |
| IPX6 | Powerful jets | Fully welded + welded closure |
| IPX7 | 30 min submerged @ 1 m | Fully welded + roll-top seal |
Never claim IPX7 on a zipped bag — even a waterproof zip (like YKK AquaGuard) drops below submersion threshold. IPX7 requires a roll-top or dry seal closure.
Use cases
- Roll-top dry bags — kayaking, boating, motorcycle touring.
- Wet-gear duffels — dive kit, wetsuit bags, water polo team bags.
- Fishing tackle bags — enclosed pockets to keep rigging dry.
- Industrial and construction totes — tool bags for outdoor sites.
Spec a welded waterproof bag
Share your target IPX rating and category; we'll return fabric options (PVC or TPU), a welded-seam construction plan and MOQ for RF-welded production.