Butyl waterproof sealant tape XJ8501
A non-curing butyl rubber membrane that stays flexible at −40 °C, stretches to 400% and seals metal roofing, RV shells, window flashing and membrane laps without a primer.
XJ8501 is a self-adhesive butyl waterproof sealant tape: a non-curing butyl rubber layer on a release liner, used for flashing, sealing and leak repair on metal roofs, RVs, windows and membrane joints. Measured properties include 1.33 ± 0.05 g/cm³ density, 400% elongation, 0.12 MPa compressive strength, 70% recovery and no cracking at −40 °C, with 2000 hours at 68 °C weathering without failure. It does not cure, so it follows movement instead of cracking at the edge.
Also searched as butyl waterproof tape · butyl sealing tape · RV roof repair tape · tuff tape · flashing tape · waterproof repair tape
How butyl differs from a bitumen flashing tape
Butyl rubber does not cure. It stays tacky and mobile, so it follows the differential movement between a metal roof sheet and a wall instead of cracking at the edge. Bitumen tape is cheaper and stiffer; it performs on a flat, static lap and fails on anything that moves or gets hot.
RV, roofing and flashing work
The same roll covers three jobs that look different but are not: an RV roof seam, a metal roof lap and a window flashing are all a joint between two materials that move at different rates. Because the tape stays flexible from −40 °C to the temperatures a dark roof reaches in summer, it seals all three with the same method — clean, dry, press, roll.
On an RV shell, the tape is also asked to survive UV and washing. A foil-faced or coated version is the one to specify where the tape stays exposed; where it is covered by a trim or a lap, the plain butyl is enough.
What to check before ordering
- Substrate: metal, membrane, wood or masonry — and whether it will be primed.
- Exposure: covered by a trim, or permanently visible and UV-exposed.
- Width and length per roll, and whether a liner split is needed for fast installation.
- Temperature at application: butyl needs a dry, dust-free surface to wet out.
At a glance
| Model | XJ8501 |
|---|---|
| Common size | 50 mm × 5 m; other widths and lengths made to order |
| Density | 1.33 ± 0.05 g/cm³ |
| Elongation | 400% |
| Recovery | 70% |
| Compressive strength | 0.12 MPa |
| Low temperature | No cracking at −40 °C |
| Water vapour transmission | 1.0 g/m²·24h |
| Service life | 20 years |
| Typical use | Metal roofing, RV roof and shell repair, window flashing, membrane laps |
Specification questions
What temperature range does XJ8501 handle?
No cracking at −40 °C, and 2000 hours at 68 °C with good weathering results. In service it stays flexible rather than curing hard.
Can it be used on a wet surface?
No. Butyl needs a dry, dust-free substrate to wet out. Damp surfaces are the most common cause of a tape that lifts at the edge after a season.
How long does it last?
The service life is rated at 20 years in a covered or protected detail. Where the tape is permanently exposed to sun, specify the foil-faced version rather than the plain butyl.
Is it the same tape used for RV roof repair?
Yes. RV roof repair tape is this butyl membrane in a narrower roll; the material and the method do not change, only the width and the facing.
What a quotation needs from you
That is all a quotation needs. We reply within four working hours, China time, with packing, loading plan and lead time — not a price list.
- Manufacturer since 2005
- 36 categories, one container
- Private label or neutral packing
- ISO 9001 & ISO 45001 certified
Enquiry received
We reply within four working hours, China time. For anything urgent, WhatsApp +86 139 6270 9169.
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