On 9/16/2019 11:10 PM, David Scheidt wrote:
patrick wrote:
:Just got back to riding after 6 months off and had a couple of problems
:with patches. Using the usual abrade/clean - alky or acetone then lay
:down the glue, wait to dry , apply patch and wait a bit. Tried several
:and had the patch peel away under a bit of stretching of the tube.
:thought there might be something amiss with the adhesive and the result
:with the different brand of valcanising fluid was the same. The patches
:themselves were not sticking to the alum base sheet and the plastic was
:intact on the peel way.They felt as flexible as new so I don't think the
atches themselves were bad but I can't speak to the cold vulcanzing
:agent that's supposed to be activated by the fluid in the tube Going to
:buy a couple patch kits before I commit to another couple boxes of rema
:small/large patches. Again 6-8 yr old patches out of the box (stored at
:ambient temps SoCal- hottish summers but the restf the yr pretty mild -
:coastal). Thoughts?? Thanks Pat

The inner (tube facing) surface of a patch consists unvulcanized
rubber and a vulcanizing ultra-acclerator (usually a zinc
thiocarbamate, but the details are propertietary, of course). The
ultra-accelerator is supposed to be inactive, until it's activate. In
normal usage, the vulcanizing fluid contains an activator (usually a
thiazole), which activates the ultra-accellerator, and voilla!,
instantly vulcanized repair. Heat in storage can set the patches off,
as can exposure to various chemicals. The box of patches I've got
says I bought them in 2011. They, and the bottle of vulcanizing fluid
(dated 2013) worked fine when I used them a few weeks ago. But
they've been stored either at my office or my baseement, neither of
whcih get hot.

That's a _lot_ more chemistry than I've ever understood, but I agree in
principle with David. I have patches that qualify as ancient -
particularly, the oval Rema Tip-Top ones that are almost two inches
long. Whenever I finally use up all the round patches in a box, there
are a couple of those left over. They sit around for years in my
basement drawer, but I've never had one fail when I've finally found a
use for it.


--
- Frank Krygowski