REMA patches

On Sep 17, 6:36*pm, AMuzi wrote:
Jobst Brandt wrote:
Someone wrote:

As I looked at the stock of new REMA Tip Top patches at the
bicycle shop today, I was greatly dismayed to see that the
ancients of REMA are gone and that the new generation is from
the same mentality as the representative whom I met at
InterBike two years ago. Â That man believed in drying the
rubber cement completely and not removing the cellophane, and
what for if the volatiles that make patches cure to become
part of the inner-tube have already evaporated.

I'm waiting for you to explain the chemistry of that. Â The
volatiles are there to attack the surface the cement is
applied to. Â The reaction that occurs is that sulphur
cross-links the rubber of the tube to the rubber of the cement
to the specially prepared face gum of the patch. Â Hexane or
trichloroethylene is not involved in the reaction. Â That's why
you let it evaporate first. Â You don't need to worrry about
the rubber in the cement vulcanizing to the tube before the
repair is installed, because it requires activation -- which
is supplied by the specially prepared face gum of the repair
unit. Â YOu can allow the cement to dry for days, or a month,
if you care to, and the repair will stick to it just fine.

I suppose you missed the item citing how van der Waals forces
are involved in adhesion. Â You might review that because
repeating it is tedious, there being many fine points.

The perforated line on the cellophane is gone so you can't
pull it off because they don't want you to. Â If you try to
pull it off, the patch comes off with it as it is peeled from
one edge instead of from the center.

As I said, this method of patching leaves a temporary patch
that is so poorly bonded that it can easily be pulled off by
hand... or separate from riding deformation aided by
inflation pressure.

I've patched a few thousand tires and tubes, on everything
from bicycles to cars, trucks and earthmoving equipment. Â I
have never had one single failure of a patch, using the
methods specified by the repair manufacturer. Â And every
supplier of cemented patches and repair units specifies
allowing the solvent to evaporate. Â Every single one, without
exception.

To make up for that I have seen a similar number of failed
patches from people who followed the "let the glue dry"
procedure and found a way to cleanly remove these failures and
replace them with patches that could not be removed and did not
leak. Â I think my example of the REMA man at InterBike two
years ago is a perfect example of why one should not follow
their write-up.

Patch failure is frequently associated with poor surface
preparation. *You would have to do some investigation before
claiming a particular patch failure had anything to do with
whether the vulcanizing fluid was wet or dry at the time of
patch application.

I guess you missed the description why the rubber cement must be
semi liquid (gelled) when the patch is applied and why the REMA
patches had a special cellophane cover that could be pulled off a
freshly placed patch.

No, you said:

"... I have seen a similar number of failed patches from people
who followed the "let the glue dry" procedure and found a way to
cleanly remove these failures and replace them with patches that
could not be removed and did not leak. Â I think my example of the
REMA man at InterBike two years ago is a perfect example of why
one should not follow their write-up."

My point is simply that patch failure frequently results from poor
preparation of the tube surface (failing to fully remove mould
release). Â You don't know if the people who "let the glue dry" had
patch failures because they let the glue dry or because of poor
preparation. Â You would have to rule out the latter to confirm the
former.

I would contend that if you can remove the patches cleanly, as
Jobst claims to have done, the rubber solution was never properly
applied to the tube in the first place. Â The most likely reason for
that would be failure to remove the mould release.

That's one that I find interesting. *I have been quite successful
removing patches cleanly, if not easily, using a solvent such as
toluene. *I don't recall why I settled on that as a solvent. *I
think it was because I saw that in some rubber cement.

It's usually pretty difficult to get the edge started but then
becomes easier when working on the interface using a saturated
Q-tip. *I have tried the suggested heat method with minimal success.
Using my method I am not aware of any visible sign of the patch
location after removal.

I haven't tried solvent and especially toluene, a solvent not found
around my house. *I just recall that it has warnings of toxicity:

*http://emedicine.medscape.com/article/818939-overview

Jobst Brandt

It's the main ingredient of commercial patch buffing solution.
Hell, everything is dangerous to some extent. Toluene is
effective and one uses such a small amount I can't believe
it's any worse than breathing the dust from sanding a lead
filled frame dent. Or riding between buses every morning.

--
Andrew Muzi
* www.yellowjersey.org/
* Open every day since 1 April, 1971- Hide quoted text -

- Show quoted text -

NAPA's tire glue can contains significant toolene and related higly
volatile cleaning and application chemicals. If youn known the guys
down at the tire shjop then nyou'ee understand these chemicals are not
neurallllly or pulmonary damging.
I bought a can for another crack at slime filled tire puncture repair
and %^%$$DF!! if the **UU^^%T!!XC tires refused to puncture until the
volatiles had escaped in extreme heat.

learn something new.....
unnnngh those covers are bitch to get off and then apply the patch
wrinklefree.
especially in the Alps.
think fiberglass ?