How do patches work?

[carlfogel@comcast.net]

I patch tubes often with good results, but it belatedly occurred to me
that I haven't the faintest idea what I'm doing.

"Glue" below is shorthand for "cold vulcanizing fluid," which may not
be the same thing.

The ritual, as practiced by my sect, is:

1) Clean and smooth the area to be patches with sandpaper, buffing
solution, light scraping, or even more desperate measures.

Is the glue so delicate that even a little mould release powder or
grime from the inside of the tire will cause it to fail?

Is the glue so feeble that the tiny ridges defeat it?

2) Slather some glue on the area to be patched and wait five minutes
until it dries to a "tacky" state.

How much glue? Is a thick layer better, worse, or immaterial?

If waiting 5 minutes is good, is 8 or even 10 minutes better? What's
happening as the glue sits on the tube? Is it doing something to the
rubber, or is it just changing itself? Is it ordinary glue (or cement,
whatever that is), or something utterly different? Should I be ashamed
to call it glue instead of cold vulcanizing fluid?

3) Peel the cellophane or plastic or whatever it is off the patch and
press the patch onto the "tacky" spot.

What's the cover for? Just to keep the patch clean, or to cover some
special stuff that reacts with the "cold fluid vulcanized" area, like
a two-part expoxy? Could you just slap the patch on upside-down and
get the same results? The "right" side of the patch is usually a
different color.

Does it matter how hard you press the patch onto the tube? It's often
said that the roller tools are really just for mooshing air bubbles
out from under big automotive patches. Does pressure matter, or can
you just smooth the patch down gently with one finger?

4) Wait until tomorrow for the patch to "cure" in place.

I'm in no hurry, but what's happening? Are volatile chemicals slowly
evaporating? Is some slow chemical change taking place? One hour? Four
hours? Twelve? Is my habit of waiting until the same-time-tomorrow to
inflate the tube and look for more punctures overkill? Or would the
patch be even stronger if I waited _two_ days?

5) Would some rubber cement stolen from an office desk drawer and a
piece cut out of an old inner tube work just as well? Would it matter
if I tried to patch a natural latex tube with a chunk of synthetic
butyl, or vice-versa?

6) How do those quick glueless patches work, the ones that look like
clear plastic? Are they the same thing, or an entirely different
process?

***

As I said, my patches work well enough. I'm just wondering about the
really trivial technical details of whatever the hell I'm doing.

Cheers,

Carl Fogel

[Christopher Harrison]

I can't answer all your questions, but -- as far as I understand it --
the "glue" changes the structure of the rubber on the tube. When it
makes it tacky, the rubber has the structure that will allow it to
bond with other rubber (i.e. the patch): kind of like Velcro. When
it's curing (I never do this: it seems fine immediately after), the
glue and two rubber surfaces set together; hence sealing the hole...
As such, I would imagine that you don't really need much glue at all;
just enough to cover the surface of the tube where the puncture is.
Don't take my word on the above. Someone who knows what they're
talking about will no-doubt correct me!

Christopher

[Brian Huntley]

On Jun 11, 4:11 pm, carlfo...@comcast.net wrote:

> Is the glue so feeble that the tiny ridges defeat it?

> 3) Peel the cellophane or plastic or whatever it is off the patch and
> press the patch onto the "tacky" spot.

> 5) Would some rubber cement stolen from an office desk drawer and a
> piece cut out of an old inner tube work just as well?

1) The ridges defeat the mechanical seal, not the glue itself.

3) No, you peel the FOIL side off. The plastic or wax paper covering
is on the top of the patch - I leave that on until I'm ready to use
the tube, personally.

5) Rubber cement works, based on my experience. Using an old bit of a
tube would likely work, too, but it would be thicker than a normal
patch, causing a 'constriction' when inflated, and would also have
'square' edges that would cause tire <-> patch friction, it seems to
me. Proper patches are a dime each at my LBS and very thin.

[Ben C]

On 2008-06-11, carlfogel@comcast.net <carlfogel@comcast.net> wrote:
> I patch tubes often with good results, but it belatedly occurred to me
> that I haven't the faintest idea what I'm doing.

Neither have I but I will "answer" your questions with my own
superstitious opinions anyway :)

> "Glue" below is shorthand for "cold vulcanizing fluid," which may not
> be the same thing.
>
> The ritual, as practiced by my sect, is:
>
> 1) Clean and smooth the area to be patches with sandpaper, buffing
> solution, light scraping, or even more desperate measures.
>
> Is the glue so delicate that even a little mould release powder or
> grime from the inside of the tire will cause it to fail?
>
> Is the glue so feeble that the tiny ridges defeat it?

It usually works OK if you skip the surface preparation if for example
you lost the bit of sandpaper in the repair kit.

> 2) Slather some glue on the area to be patched and wait five minutes
> until it dries to a "tacky" state.
>
> How much glue? Is a thick layer better, worse, or immaterial?
>
> If waiting 5 minutes is good, is 8 or even 10 minutes better? What's
> happening as the glue sits on the tube? Is it doing something to the
> rubber, or is it just changing itself?

I assume that what's happening is that a solvent in the glue is
evaporating. Wait too long and it might dry out, not long enough and the
solvent won't have anywhere to go so the glue will never set properly.

That's how most glue of the kind that just comes in one tube works, as
opposed to the kind that comes in two tubes that you mix together.

I usually can't be bothered to wait 5 minutes so blow on the glue/stuff
instead, which makes it go kind of cloudy. This passes the time and
seems to work acceptably.

> Is it ordinary glue (or cement, whatever that is), or something
> utterly different? Should I be ashamed to call it glue instead of cold
> vulcanizing fluid?
>
> 3) Peel the cellophane or plastic or whatever it is off the patch and
> press the patch onto the "tacky" spot.
>
> What's the cover for? Just to keep the patch clean, or to cover some
> special stuff that reacts with the "cold fluid vulcanized" area, like
> a two-part expoxy? Could you just slap the patch on upside-down and
> get the same results? The "right" side of the patch is usually a
> different color.

I think the cover just keeps it clean. Repairing tubes with bits cut out
of other tubes never seems to work very well though.

> Does it matter how hard you press the patch onto the tube? It's often
> said that the roller tools are really just for mooshing air bubbles
> out from under big automotive patches. Does pressure matter, or can
> you just smooth the patch down gently with one finger?
>
>
> 4) Wait until tomorrow for the patch to "cure" in place.

I never do that.

> I'm in no hurry, but what's happening? Are volatile chemicals slowly
> evaporating? Is some slow chemical change taking place? One hour? Four
> hours? Twelve? Is my habit of waiting until the same-time-tomorrow to
> inflate the tube and look for more punctures overkill? Or would the
> patch be even stronger if I waited _two_ days?

I don't know but the time it takes to put the tyre and wheel back on is
usually enough.

[Michael Press]

In article
<7beee042-dcf4-470a-a709-39e95d3c9b53@m36g2000hse.googlegroups.com>,
Christopher Harrison <SpamFactory@chrisharrison.co.uk> wrote:

> I can't answer all your questions, but -- as far as I understand it --
> the "glue" changes the structure of the rubber on the tube. When it
> makes it tacky, the rubber has the structure that will allow it to
> bond with other rubber (i.e. the patch): kind of like Velcro. When
> it's curing (I never do this: it seems fine immediately after), the
> glue and two rubber surfaces set together; hence sealing the hole...
> As such, I would imagine that you don't really need much glue at all;
> just enough to cover the surface of the tube where the puncture is.
> Don't take my word on the above. Someone who knows what they're
> talking about will no-doubt correct me!

Butyl rubber is a cross-linked polymer. It is impervious
to chemical transformation short of outright destruction.
Patch glue works by surface adhesion. Glue adheres better
to a clean surface, but it remains a physical bond, not
a chemical bond. Peel a patch off a tube and observe that
the surface of the tube is chemically unchanged.

--
Michael Press

[Dan O]

On Jun 11, 2:54 pm, Ben C <spams...@spam.eggs> wrote:
> On 2008-06-11, carlfo...@comcast.net <carlfo...@comcast.net> wrote:
>

<snip>

>
> > 2) Slather some glue on the area to be patched and wait five minutes
> > until it dries to a "tacky" state.
>
> > How much glue? Is a thick layer better, worse, or immaterial?
>
> > If waiting 5 minutes is good, is 8 or even 10 minutes better? What's
> > happening as the glue sits on the tube? Is it doing something to the
> > rubber, or is it just changing itself?
>

<snip>

>
> I usually can't be bothered to wait 5 minutes so blow on the glue/stuff
> instead, which makes it go kind of cloudy. This passes the time and
> seems to work acceptably.
>

It's more fun to ignite the glue and watch it burn out, then apply the
patch immediately. (Thick layer burns longer, leaving the tube
hotter :-)

[Leo Lichtman]

"Dan O" wrote: It's more fun to ignite the glue and watch it burn out,
(clip)
^^^^^^^^^^^^^^^^^^^
That used to be a common practice in the old automobile inner tube days,
before "hot patches" came into use. The people I remember doing this also
used to spit on the curb and then and then sharpen their pocket knives. The
ones who chewed tobacco didn't generally do this at the same time.

Someone should invent a hot patch/ CO2 inflater combo for bicyclists who
don't care how much their tools weigh. I can't recall ever hearing of a hot
patch that didn't hold.