Peeling PU layer

Discussion in 'DIY & MYOG' started by Meadows, Jul 11, 2017.

  1. Meadows

    Meadows Section Hiker

    I've an old berghaus waist pack I'm thinking of resurrecting but the PU layer on the inside has semi flaked/peeled off.
    Is there anything I can do to stop it getting worse or better still improve the bags waterproofness? (Not sure that's a proper word)

    Options so far thought of

    A. Use a pack liner of sorts. Seems the easiest but might not fit with how I use the bag and still allows the bag to get soggy.

    B. Waterproof PVA glue, thinned and 'painted' on to the internal surface.

    C. Dilute silicone sealer applied to the outside of the fabric.

    Any help or ideas welcome.
  2. kamov

    kamov Trail Blazer

  3. Shewie

    Shewie Administrator Staff Member

    What about removing the old flaky stuff and applying silicone to the inside?
    stormin', Meadows and Tartanferret like this.
  4. Teepee

    Teepee Thru Hiker

    There is nothing you can do to save the PU coating. Water eventually dissolves PU, it's had it. A stiff brush works well for removing the flaky stuff.

    Re-applying PU is the best bet IME, rather than silicone. The Tent sure is PU but I've not used it.

    My goto method for repairing PU coatings is PU glue, like Mcnett Seamgrip or Wilkinson rubber glue, thinned with Xylene (Hammerite thinners) and then painted on
    slovhike likes this.
  5. Meadows

    Meadows Section Hiker

    Thanks folks, it's all very helpful.

    What have been the problems with silicone, did you go with outside or inside?
  6. Teepee

    Teepee Thru Hiker

    There are a number of issues with silicone that don't occur with PU.

    The thinner weakens the set silicone.
    Silicone generally sets much more quickly, meaning it doesn't penetrate as well.
    Makes a weaker coating.
    Doersn't waterproof as well as PU.
    Creates future adhesion problems, not even silicone likes sticking to silicone.
    Very short pot life when thinned.

    Compared to my home coating of PU, silicone isn't in the same league.

    PU always put on the inside, it's not as UV resistant as silicone.
    Last edited: Jul 13, 2017
    Meadows and cathyjc like this.
  7. Ken T.

    Ken T. Section Hiker

    Or take it as a sign to move on.
  8. Meadows

    Meadows Section Hiker

    That's great thanks PU it is then.

    @Ken T. I'm from Yorkshire, it's make do and mend... or nowt!
  9. Scotty Von Porkchop

    Scotty Von Porkchop Ultralighter

    How do you reapply the PU @Teepee? Is it PU impregnated treatment rather than the more usual layer in the fabric milling?

    I've lost the PU on a couple of really good bags and found the silicone treatment OK but it depends on the weave as to how waterproof it'll be. The heavy weight 500d cordura types didn't work well
  10. Teepee

    Teepee Thru Hiker

    It's just brushed on @Scotty Von Porkchop. It tends to be quite gloopy, a stiff brush works well. It flows out like a paint and levels itself.

    PU is usually a coating IME, rather than a full impregnation like a quality silnylon.
  11. Scotty Von Porkchop

    Scotty Von Porkchop Ultralighter

    Cheers @Teepee, sounds good actually as we've all got gear that we just can't give up on (my mom's got a garages full ☺️)

    I've use the impregnated PU fabrics a few times now and actually rate them where the slippy nature of silnylon isn't wanted
  12. slovhike

    slovhike Thru Hiker

    @Teepee so any PU glue thinned with Xylene containing thinner should work?
  13. Teepee

    Teepee Thru Hiker

    @slovhike ; I think so..... I've thinned Seamgrip, Wilko's PU glue and also 500ml tubes of CT1. All have worked well and lasted, the CT1 sets weaker though.

    It does dissolve Sikaflex too.
    slovhike and Chiseller like this.
  14. Chiseller

    Chiseller Thru Hiker

    Mmmmm sika flex... I can cadge that. My ULA ohm has the pu coating peeling off... Bit disappointed as it's only been used a couple of dozen times from new!
  15. Meadows

    Meadows Section Hiker

    That seems wrong to me @Chiseller, how old is it?
  16. Teepee

    Teepee Thru Hiker

    I'm not 100% sure, but think the Ohm is Dyneema Gridstop: Acrylic coated? Hence the softer hand and low HH.
  17. Chiseller

    Chiseller Thru Hiker

    I ordered it on the 14 October last year... By eck where's the year gone?
    It is Dyneema Gridstop
  18. Meadows

    Meadows Section Hiker

    Did you buy direct @Chiseller , I'd be looking at the warranty period.
    Chiseller likes this.
  19. Chiseller

    Chiseller Thru Hiker

    Bought it from ultralight gear. I'll put some pics up
    20171005_224054.jpg 20171005_224054.jpg 20171005_224010.jpg
  20. Meadows

    Meadows Section Hiker

    I'd not be happy with that with less than a months constant use.
    Anybody else had such issues?
  21. NEEpps

    NEEpps Ultralighter

    My Ohm2 does not have any coating, just straight Gridstop. Bought it direct from ULA, only other difference is that it is a roll top.
  22. Shewie

    Shewie Administrator Staff Member

    PU can break down if stored away wet, I've seen tent fly sheets do the same.
    Could that be the cause Chis?
    All my ULA packs (x5) are still going strong.
  23. Chiseller

    Chiseller Thru Hiker

    No, not been stored wet and if it has been wet, it's been air dried. It's the area where the small clip on pocket sits against.
  24. Teepee

    Teepee Thru Hiker

    PU swells and weakens as it gets wet. Some PU fabric coatings are slightly water soluble too, a few days of being wet and they are past their best; the stays wet more than any other part and often gets sat on wet ground.

    TBH, I've seen a PU coated pack that doesn't fail pretty quickly.
  25. Meadows

    Meadows Section Hiker

    It might be worth an email or call to ULOG to see what they say, I 've never had a bag go that quickly.
    Chiseller likes this.

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