Elmer's Rubber Cement is not the vulcanizing kind!

On Apr 24, 8:58*pm, (Tom Keats) wrote:
* * * * Tom Sherman writes:

Where can I buy (in bulk) a large amount of the vulcanizing cement
from at the best price?

I was under the impression that vulcanizing requires heat and a curative
to produce cross-linking of the polymers, and "vulcanizing fluid" is a
marketing term.

As I understand it, so-called "vulcanizing" rubber cement
chemically integrates with the existing rubber to which
it is applied. *This effect should be desirable with
regard to tire repairs, since holes in tires are external
and thereby exposed to all kinds of stresses and tensions.

I've long been under the impression that patch kit cement
is of the vulcanizing kind, but upon further research I'm
prepared to admit to error on my part.

If patch kit rubber cement truly is non-vulcanizing, it
nevertheless works for inner tube patches when it's properly
applied, the layers of cement are allowed to set ("cure")
for a few minutes before applying patch to hole, and the
patched tube is rested overnight before inflating.

I suspect the reason for letting the cement dry for a
few minutes before sticking the patch on, is to let it
become more viscous so that Surface Tension pulls (pushes?)
the patch more firmly into place against the tube. *I think
the "good" rubber cement for tube patching has a solvent
in it, like acetone or some kind of pentane or other volatile
solvent who's job is to *keep it storable & fluid enough
to spread it, and that's the solvent's only purpose. *Once
the cement is applied, the next step is to let that solvent
evaporate so the remaining cement can do it's job.

What is vulcanizing? From

http://en.wikipedia.org/wiki/Vulcanization

"Vulcanization or vulcanisation refers to a specific curing process
of rubber involving high heat and the addition of sulfur or other
equivalent
curatives. It is a chemical process in which polymer molecules are
linked
to other polymer molecules by atomic bridges composed of sulfur atoms
or carbon to carbon bonds. The end result is that the springy rubber
molecules become cross-linked to a greater or lesser extent. This
makes
the bulk material harder, much more durable and also more resistant
to
chemical attack. It also makes the surface of the material smoother
and
prevents it from sticking to metal or plastic chemical catalysts."

And so on. It should be apparent that patch cement
does not "vulcanize." It's a sales term.

I patch tubes with rubber cement out of a jar. My
current jar is Elmer's. I don't have problems with
patches coming off or failing. I've even patched cuts
without an official patch, using rubber cement from
the jar and a piece of old inner tube. You have to be
very scrupulous about removing the mold release
for this to work. I did it as a challenge to see if
I could fix a cut without putting in a very large
stiff patch.

I let the cement dry pretty thoroughly before
applying patches. I also rub them on with a
tire lever end or similar. Contrary to your speculation
about humidity and pressure (the pressure
difference is small and couldn't be significant),
I do most of my patching in low humidity
since I live in a dry place.

IMO, most patch failures are due to improper
preparation or rushing.

Ben

On Sat, 25 Apr 2009 10:14:44 -0700, (Tom Keats)
wrote:

In article ,
writes:
On Fri, 24 Apr 2009 20:58:24 -0700, l (Tom
Keats) wrote:

In article ,
Tom Sherman writes:
Ablang ? wrote:
I bought a 4oz jar (UPC 0 269050 8) of this stuff from Home Depot last
year for about $2.50. Pretty cheap stuff.

I finally got a chance to use these on my inner tubes for my 27" x
1-1/4" tires (100 psi) and found out that they don't really stick
permanently. The next day I discover that some part of the patch has
breached.

In trying to figure out what I did wrong (I have successfully patched
other tires before using the glue from patch kits), I figure it's that
I'm either using too thick of a layer of Elmer's or that this rubber
cement really isn't the vulcanizing kind.

What do you guys think?

Where can I buy (in bulk) a large amount of the vulcanizing cement
from at the best price?

I was under the impression that vulcanizing requires heat and a curative
to produce cross-linking of the polymers, and "vulcanizing fluid" is a
marketing term.

As I understand it, so-called "vulcanizing" rubber cement
chemically integrates with the existing rubber to which
it is applied. This effect should be desirable with
regard to tire repairs, since holes in tires are external
and thereby exposed to all kinds of stresses and tensions.

I've long been under the impression that patch kit cement
is of the vulcanizing kind, but upon further research I'm
prepared to admit to error on my part.

If patch kit rubber cement truly is non-vulcanizing, it
nevertheless works for inner tube patches when it's properly
applied, the layers of cement are allowed to set ("cure")
for a few minutes before applying patch to hole, and the
patched tube is rested overnight before inflating.

I suspect the reason for letting the cement dry for a
few minutes before sticking the patch on, is to let it
become more viscous so that Surface Tension pulls (pushes?)
the patch more firmly into place against the tube. I think
the "good" rubber cement for tube patching has a solvent
in it, like acetone or some kind of pentane or other volatile
solvent who's job is to keep it storable & fluid enough
to spread it, and that's the solvent's only purpose. Once
the cement is applied, the next step is to let that solvent
evaporate so the remaining cement can do it's job.

I might be wrong about that, too -- I'm just guessing.
Maybe Jobst will set us all straight.

Maybe it's better to patch inner tubes during a rainy day,
when the air pressure is higher? Surface tension, 'n
all that.


cheers,
Tom

Dear Tom,

"Rubber cement works by a mechanism of cohesion [also called
autohesion, or 'self-sticking-to-self] but this is true both for the
paper gluing example and the rubber gluing example, provided there is
cement on both pieces of paper."

"Cohesion occurs when the long polymer chains of the adhesive material
are able to penetrate and mix with the polymer chains of the adherend
[the substrate]. This process is also called 'interdigitation' in
reference to the simile of fingers of opposite hands interlaced, as if
in prayer. It is much harder to separate hands with interlaced fingers
than when the hands simply lay one on the other."

"When rubber cement is used to bond rubber to itself, the solvent in
the cement swells the substrates somewhat and facilitates the
interdigitation process. After the solvent evaporates, it is hard to
distinguish just where the joint lies. The bonding force is not a
chemical bond -- no bonds are made or broken; the strength of the bond
is purely a physical phenomenon involving van der Walls and London
forces between two intimately mixed and chemically similar non-polar
hydrocarbon rubber molecules."
http://www.madsci.org/posts/archives...3004.Ch.r.html

Thanks, Carl. I'm now edified. I have for a long time
noted how patches seem to be either pulled or pushed
onto the surfaces to which they're adhered, and I've
casually wondered about whatever processes might be
at work, but I've never actually gotten around to
verbially articulating my puzzlement. Now I'm wondering
how those long polymers find their ways into their holes
or ruts or whatever allows them to interdigitate -- do
they just fall in when a hole opens up beneath them,
or do they just randomly flow around until they drop
into a hole/rut/whatever? If they're electrically drawn
in, could that arguably be a chemical process?

I am nevertheless still mystified by how a properly
applied patch seems to be either pushed or pulled
into place, as if an invisible thumb had been pressing
on it all night long. The patch doesn't just lie there
like a fillet of sole or a postage stamp -- some force
has snuggled it intimately right up to the inner tube,
as if patch & tube are spooning. If it's those long
polymer thingies, they must act like an octopus's
tentacles drawing its prey to its beak. But to the
best of my limited knlowledge, molecules don't possess
volition.

I guess the clue lies in whatever keeps an improperly
applied patch from working.

But I have another poser for you, if you're inclined to
spend even more time in response: what does so-called
"vulcanizing" rubber cement do, that non-vulcanizing
rubber cement doesn't?

During my more austere days, I found that vulcanizing
rubber cement works better than non-vulcanizing
rubber cement (or contact cement for that matter) for
minor, external ~tire~ repairs. A swatch of jeans denim
slathered with contact cement makes a fairly usable
internal boot, but you can feel the lump with each
wheel rotation.


cheers,
Tom

Dear Tom,

Rubber cement works by interdigitation, with no chemical changes. It
doesn't vulcanize the rubber pieces, meaning that no cross-links are
formed and no chemical changes occur.

Cold vulcanizing fluid contains chemicals (the "accelerators" below)
that do produce cross-links between the rubber molecules, just as hot
vulcanizing (heat plus sulphur) changes the chemical structure of
rubber.

The wait-until-tacky prescription for cold vulcanizing fluid has a
surprisingly simple explanation:

"Vulcanizing fluid has two primary functions. First, it contains
chemical accelerators which vulcanize the repair to the tire. Second,
when dry, it leaves the prepared surface tacky, which helps hold the
repair in place until vulcanization occurs."
http://www.premaproducts.com/Technic...3c9abed.0.html

Cheers,

Carl Fogel

On Sat, 25 Apr 2009 21:37:09 -0700 (PDT), "
wrote:

On Apr 24, 8:58*pm, (Tom Keats) wrote:
* * * * Tom Sherman writes:

Where can I buy (in bulk) a large amount of the vulcanizing cement
from at the best price?

I was under the impression that vulcanizing requires heat and a curative
to produce cross-linking of the polymers, and "vulcanizing fluid" is a
marketing term.

As I understand it, so-called "vulcanizing" rubber cement
chemically integrates with the existing rubber to which
it is applied. *This effect should be desirable with
regard to tire repairs, since holes in tires are external
and thereby exposed to all kinds of stresses and tensions.

I've long been under the impression that patch kit cement
is of the vulcanizing kind, but upon further research I'm
prepared to admit to error on my part.

If patch kit rubber cement truly is non-vulcanizing, it
nevertheless works for inner tube patches when it's properly
applied, the layers of cement are allowed to set ("cure")
for a few minutes before applying patch to hole, and the
patched tube is rested overnight before inflating.

I suspect the reason for letting the cement dry for a
few minutes before sticking the patch on, is to let it
become more viscous so that Surface Tension pulls (pushes?)
the patch more firmly into place against the tube. *I think
the "good" rubber cement for tube patching has a solvent
in it, like acetone or some kind of pentane or other volatile
solvent who's job is to *keep it storable & fluid enough
to spread it, and that's the solvent's only purpose. *Once
the cement is applied, the next step is to let that solvent
evaporate so the remaining cement can do it's job.

What is vulcanizing? From

http://en.wikipedia.org/wiki/Vulcanization

"Vulcanization or vulcanisation refers to a specific curing process
of rubber involving high heat and the addition of sulfur or other
equivalent
curatives. It is a chemical process in which polymer molecules are
linked
to other polymer molecules by atomic bridges composed of sulfur atoms
or carbon to carbon bonds. The end result is that the springy rubber
molecules become cross-linked to a greater or lesser extent. This
makes
the bulk material harder, much more durable and also more resistant
to
chemical attack. It also makes the surface of the material smoother
and
prevents it from sticking to metal or plastic chemical catalysts."

And so on. It should be apparent that patch cement
does not "vulcanize." It's a sales term.

I patch tubes with rubber cement out of a jar. My
current jar is Elmer's. I don't have problems with
patches coming off or failing. I've even patched cuts
without an official patch, using rubber cement from
the jar and a piece of old inner tube. You have to be
very scrupulous about removing the mold release
for this to work. I did it as a challenge to see if
I could fix a cut without putting in a very large
stiff patch.

I let the cement dry pretty thoroughly before
applying patches. I also rub them on with a
tire lever end or similar. Contrary to your speculation
about humidity and pressure (the pressure
difference is small and couldn't be significant),
I do most of my patching in low humidity
since I live in a dry place.

IMO, most patch failures are due to improper
preparation or rushing.

Ben

Dear Ben,

Google for "cold vulcanizing fluid"--it's a widely used term in the
industrial belt industry.

Cold vulcanizing fluid simply uses chemicals that produce the
cross-linking that's one of features of hot vulcanization.

In contrast, plain rubber cement works by interdigitation without the
chemical changes of cross-linking--rubber cement isn't cold
vulcanizing fluid.

Cheers,

Carl Fogel

In article ,
l (Tom Keats) wrote:

In article ,
Tom Sherman writes:
Ablang ? wrote:
I bought a 4oz jar (UPC 0 269050 8) of this stuff from Home Depot last
year for about $2.50. Pretty cheap stuff.

I finally got a chance to use these on my inner tubes for my 27" x
1-1/4" tires (100 psi) and found out that they don't really stick
permanently. The next day I discover that some part of the patch has
breached.

In trying to figure out what I did wrong (I have successfully patched
other tires before using the glue from patch kits), I figure it's that
I'm either using too thick of a layer of Elmer's or that this rubber
cement really isn't the vulcanizing kind.

What do you guys think?

Where can I buy (in bulk) a large amount of the vulcanizing cement
from at the best price?

I was under the impression that vulcanizing requires heat and a curative
to produce cross-linking of the polymers, and "vulcanizing fluid" is a
marketing term.

As I understand it, so-called "vulcanizing" rubber cement
chemically integrates with the existing rubber to which
it is applied. This effect should be desirable with
regard to tire repairs, since holes in tires are external
and thereby exposed to all kinds of stresses and tensions.

I've long been under the impression that patch kit cement
is of the vulcanizing kind, but upon further research I'm
prepared to admit to error on my part.

If patch kit rubber cement truly is non-vulcanizing, it
nevertheless works for inner tube patches when it's properly
applied, the layers of cement are allowed to set ("cure")
for a few minutes before applying patch to hole, and the
patched tube is rested overnight before inflating.

I suspect the reason for letting the cement dry for a
few minutes before sticking the patch on, is to let it
become more viscous so that Surface Tension pulls (pushes?)
the patch more firmly into place against the tube. I think
the "good" rubber cement for tube patching has a solvent
in it, like acetone or some kind of pentane or other volatile
solvent who's job is to keep it storable & fluid enough
to spread it, and that's the solvent's only purpose. Once
the cement is applied, the next step is to let that solvent
evaporate so the remaining cement can do it's job.

I might be wrong about that, too -- I'm just guessing.
Maybe Jobst will set us all straight.

Maybe it's better to patch inner tubes during a rainy day,
when the air pressure is higher? Surface tension, 'n
all that.

Air pressure has no first order effect on vapor pressure
of the volatile solvent. Henry's law. A small change in
air pressure implies a third order change in solvent vapor pressure.

--
Michael Press

On Apr 24, 10:58*pm, (Tom Keats) wrote:
In article ,
* * * * Tom Sherman writes:



Ablang ? wrote:
I bought a 4oz jar (UPC 0 269050 8) of this stuff from Home Depot last
year for about $2.50. *Pretty cheap stuff.

I finally got a chance to use these on my inner tubes for my 27" x
1-1/4" tires (100 psi) and found out that they don't really stick
permanently. *The next day I discover that some part of the patch has
breached.

In trying to figure out what I did wrong (I have successfully patched
other tires before using the glue from patch kits), I figure it's that
I'm either using too thick of a layer of Elmer's or that this rubber
cement really isn't the vulcanizing kind.

What do you guys think?

Where can I buy (in bulk) a large amount of the vulcanizing cement
from at the best price?

I was under the impression that vulcanizing requires heat and a curative
to produce cross-linking of the polymers, and "vulcanizing fluid" is a
marketing term.

As I understand it, so-called "vulcanizing" rubber cement
chemically integrates with the existing rubber to which
it is applied. *This effect should be desirable with
regard to tire repairs, since holes in tires are external
and thereby exposed to all kinds of stresses and tensions.

I've long been under the impression that patch kit cement
is of the vulcanizing kind, but upon further research I'm
prepared to admit to error on my part.

If patch kit rubber cement truly is non-vulcanizing, it
nevertheless works for inner tube patches when it's properly
applied, the layers of cement are allowed to set ("cure")
for a few minutes before applying patch to hole, and the
patched tube is rested overnight before inflating.

I suspect the reason for letting the cement dry for a
few minutes before sticking the patch on, is to let it
become more viscous so that Surface Tension pulls (pushes?)
the patch more firmly into place against the tube. *I think
the "good" rubber cement for tube patching has a solvent
in it, like acetone or some kind of pentane or other volatile
solvent who's job is to *keep it storable & fluid enough
to spread it, and that's the solvent's only purpose. *Once
the cement is applied, the next step is to let that solvent
evaporate so the remaining cement can do it's job.

I might be wrong about that, too -- I'm just guessing.
Maybe Jobst will set us all straight.

Maybe it's better to patch inner tubes during a rainy day,
when the air pressure is higher? *Surface tension, 'n
all that.

cheers,
* * * * Tom

--
Nothing is safe from me.
I'm really at:
tkeats curlicue vcn dot bc dot ca

I believe with respect to bicycle tire tube patch adhesive “Cold
vulcanizing” is a misnomer in so far as it implies that a chemical
reaction is facilitated. Here the “accelerators” – common commercial
organic solvents that under normal conditions do not chemically react
with rubber – function only as a solvent system for both the rubber
dissolved in the so called “cold vulcanizing fluid” and a partial
solvent system for the tube and the patch. This partial solvation
allows for the integration and fusion of the rubber particles of the
tube, adhesive, and the patch into a more or less homogeneous whole.
If these solvents are not allowed to volatilize sufficiently, say for
a period of twenty four hours, the tire rubber and patch rubber may
remain sufficiently solvated to allow for their easy separation. The
dissolved rubber of the tire patch adhesive – the so called “cold
vulcanizing fluid” – retains and thus slows the volatilization of its
solvents allowing for the partial solvation of the patch and tube
rubber by these solvents. There are a myriad of other rubber based
adhesives for different and specialized applications; many certainly
do undergo chemical reactions, and some of these may additionally be
termed “cold vulcanizing”.

___

Spike

In article ,
writes:

"When rubber cement is used to bond rubber to itself, the solvent in
the cement swells the substrates somewhat and facilitates the
interdigitation process. After the solvent evaporates, it is hard to
distinguish just where the joint lies.

Okay, but I still nevertheless perceive something going on
that intimates a patch together with the inner tube to
which it is applied.

The bonding force is not a
chemical bond -- no bonds are made or broken; the strength of the bond
is purely a physical phenomenon involving van der Walls and London
forces between two intimately mixed and chemically similar non-polar
hydrocarbon rubber molecules."
http://www.madsci.org/posts/archives...3004.Ch.r.html

I intuit there's something further happening. The
patch doesn't just lie there on the tube like a
flapjack; it's as if the tube is sucking the patch
onto itself. The patch & tube aren't just holding
hands and interdigitating -- they're really cleaving
unto each other and becoming one flesh, like Adam & Eve.

And with that imagery, I think I'll forego this line
of curiosity. It's enough to know how to successfully
patch a tube, without getting into all the messy,
gruesome details. Some things in life are best
left as wonderments. As long as one gets away with
not getting the patch kit instruction sheet inextricably
stuck to their thumb, life is good.


cheers,
Tom


--
Nothing is safe from me.
I'm really at:
tkeats curlicue vcn dot bc dot ca

On Apr 26, 3:44*am, wrote:
On Apr 24, 10:58*pm, (Tom Keats) wrote:



In article ,
* * * * Tom Sherman writes:

Ablang ? wrote:
I bought a 4oz jar (UPC 0 269050 8) of this stuff from Home Depot last
year for about $2.50. *Pretty cheap stuff.

I finally got a chance to use these on my inner tubes for my 27" x
1-1/4" tires (100 psi) and found out that they don't really stick
permanently. *The next day I discover that some part of the patch has
breached.

In trying to figure out what I did wrong (I have successfully patched
other tires before using the glue from patch kits), I figure it's that
I'm either using too thick of a layer of Elmer's or that this rubber
cement really isn't the vulcanizing kind.

What do you guys think?

Where can I buy (in bulk) a large amount of the vulcanizing cement
from at the best price?

I was under the impression that vulcanizing requires heat and a curative
to produce cross-linking of the polymers, and "vulcanizing fluid" is a
marketing term.

As I understand it, so-called "vulcanizing" rubber cement
chemically integrates with the existing rubber to which
it is applied. *This effect should be desirable with
regard to tire repairs, since holes in tires are external
and thereby exposed to all kinds of stresses and tensions.

I've long been under the impression that patch kit cement
is of the vulcanizing kind, but upon further research I'm
prepared to admit to error on my part.

If patch kit rubber cement truly is non-vulcanizing, it
nevertheless works for inner tube patches when it's properly
applied, the layers of cement are allowed to set ("cure")
for a few minutes before applying patch to hole, and the
patched tube is rested overnight before inflating.

I suspect the reason for letting the cement dry for a
few minutes before sticking the patch on, is to let it
become more viscous so that Surface Tension pulls (pushes?)
the patch more firmly into place against the tube. *I think
the "good" rubber cement for tube patching has a solvent
in it, like acetone or some kind of pentane or other volatile
solvent who's job is to *keep it storable & fluid enough
to spread it, and that's the solvent's only purpose. *Once
the cement is applied, the next step is to let that solvent
evaporate so the remaining cement can do it's job.

I might be wrong about that, too -- I'm just guessing.
Maybe Jobst will set us all straight.

Maybe it's better to patch inner tubes during a rainy day,
when the air pressure is higher? *Surface tension, 'n
all that.

cheers,
* * * * Tom

--
Nothing is safe from me.
I'm really at:
tkeats curlicue vcn dot bc dot ca

I believe with respect to bicycle tire tube patch adhesive “Cold
vulcanizing” is a misnomer in so far as it implies that a chemical
reaction is facilitated. *Here the “accelerators” – common commercial
organic solvents that under normal conditions do not chemically react
with rubber – *function only as a solvent system for both the rubber
dissolved in the so called “cold vulcanizing fluid” and a partial
solvent system for the tube and the patch. This partial solvation
allows for the integration and fusion of the rubber particles of the
tube, adhesive, and the patch into a more or less homogeneous whole.
If these solvents are not allowed to volatilize sufficiently, say for
a period of twenty four hours, the tire rubber and patch rubber may
remain sufficiently solvated *to allow for their easy separation. The
dissolved rubber of the tire *patch adhesive – the so called “cold
vulcanizing fluid” – retains and thus slows the volatilization of its
solvents allowing for the partial solvation of the patch and tube
rubber by these solvents. There are a myriad of other rubber based
adhesives for different and specialized applications; many certainly
do undergo chemical reactions, and some of these may additionally be
termed “cold vulcanizing”.

___

Spike

On further investigation it seems that some bicycle tire tube patch
adhesives may indeed contain rubber vulcanization accelerators. For
example the MSDS(Material Data Safety Sheet) for REMA Tip Top
Vulcanizing Fluid CFC Free indicates that it contains 1.0 – 2.5 %Wt of
N-Ethylcyclohexylamine, an amine having a number of commercial
applications including use in rubber formulations. The general
mechanism of tube patch adhesion remains, I believe, as indicated
above.

___

Spike

Tom Keats wrote:
In article ,
writes:

"When rubber cement is used to bond rubber to itself, the solvent in
the cement swells the substrates somewhat and facilitates the
interdigitation process. After the solvent evaporates, it is hard to
distinguish just where the joint lies.

Okay, but I still nevertheless perceive something going on
that intimates a patch together with the inner tube to
which it is applied.

The bonding force is not a
chemical bond -- no bonds are made or broken; the strength of the bond
is purely a physical phenomenon involving van der Walls and London
forces between two intimately mixed and chemically similar non-polar
hydrocarbon rubber molecules."
http://www.madsci.org/posts/archives...3004.Ch.r.html

I intuit there's something further happening. The
patch doesn't just lie there on the tube like a
flapjack; it's as if the tube is sucking the patch
onto itself.

oh, for ****'s sake.


The patch & tube aren't just holding
hands and interdigitating -- they're really cleaving
unto each other and becoming one flesh, like Adam & Eve.

get thine dumb religious ass off to school will ya? learn math. learn
chemistry. then quit posting this kind of crap.



And with that imagery, I think I'll forego this line
of curiosity. It's enough to know how to successfully
patch a tube, without getting into all the messy,
gruesome details. Some things in life are best
left as wonderments. As long as one gets away with
not getting the patch kit instruction sheet inextricably
stuck to their thumb, life is good.


cheers,
Tom


--
Nothing is safe from me.

nothing is safe /for/ the incurably incurious.


I'm really at:
tkeats curlicue vcn dot bc dot ca

Still Just Me wrote:
On Sun, 26 Apr 2009 04:51:06 -0700 (PDT),
wrote:

On further investigation it seems that some bicycle tire tube patch
adhesives may indeed contain rubber vulcanization accelerators. For
example the MSDS(Material Data Safety Sheet) for REMA Tip Top
Vulcanizing Fluid CFC Free indicates that it contains 1.0 � 2.5 %Wt of
N-Ethylcyclohexylamine, an amine having a number of commercial
applications including use in rubber formulations. The general
mechanism of tube patch adhesion remains, I believe, as indicated
above.

So, bottom line what are the recommended glues?

I don't use patch kits, I've always just used a piece of tube to
patch. Patch kits always seemed like a very expensive way to get a
very small tube of cement and some precut rubber in a small box.

What's a suggested glue for tube on tube patching?

are you for real? how can you read a post that just tells you mechanism
and application, yet still utterly fail to comprehend what it means?
[rhetorical]

wrote:
On Sat, 25 Apr 2009 10:14:44 -0700, (Tom Keats)
wrote:

In article ,
writes:
On Fri, 24 Apr 2009 20:58:24 -0700, l (Tom
Keats) wrote:

In article ,
Tom Sherman writes:
Ablang ? wrote:
I bought a 4oz jar (UPC 0 269050 8) of this stuff from Home Depot last
year for about $2.50. Pretty cheap stuff.

I finally got a chance to use these on my inner tubes for my 27" x
1-1/4" tires (100 psi) and found out that they don't really stick
permanently. The next day I discover that some part of the patch has
breached.

In trying to figure out what I did wrong (I have successfully patched
other tires before using the glue from patch kits), I figure it's that
I'm either using too thick of a layer of Elmer's or that this rubber
cement really isn't the vulcanizing kind.

What do you guys think?

Where can I buy (in bulk) a large amount of the vulcanizing cement
from at the best price?
I was under the impression that vulcanizing requires heat and a curative
to produce cross-linking of the polymers, and "vulcanizing fluid" is a
marketing term.
As I understand it, so-called "vulcanizing" rubber cement
chemically integrates with the existing rubber to which
it is applied. This effect should be desirable with
regard to tire repairs, since holes in tires are external
and thereby exposed to all kinds of stresses and tensions.

I've long been under the impression that patch kit cement
is of the vulcanizing kind, but upon further research I'm
prepared to admit to error on my part.

If patch kit rubber cement truly is non-vulcanizing, it
nevertheless works for inner tube patches when it's properly
applied, the layers of cement are allowed to set ("cure")
for a few minutes before applying patch to hole, and the
patched tube is rested overnight before inflating.

I suspect the reason for letting the cement dry for a
few minutes before sticking the patch on, is to let it
become more viscous so that Surface Tension pulls (pushes?)
the patch more firmly into place against the tube. I think
the "good" rubber cement for tube patching has a solvent
in it, like acetone or some kind of pentane or other volatile
solvent who's job is to keep it storable & fluid enough
to spread it, and that's the solvent's only purpose. Once
the cement is applied, the next step is to let that solvent
evaporate so the remaining cement can do it's job.

I might be wrong about that, too -- I'm just guessing.
Maybe Jobst will set us all straight.

Maybe it's better to patch inner tubes during a rainy day,
when the air pressure is higher? Surface tension, 'n
all that.


cheers,
Tom
Dear Tom,

"Rubber cement works by a mechanism of cohesion [also called
autohesion, or 'self-sticking-to-self] but this is true both for the
paper gluing example and the rubber gluing example, provided there is
cement on both pieces of paper."

"Cohesion occurs when the long polymer chains of the adhesive material
are able to penetrate and mix with the polymer chains of the adherend
[the substrate]. This process is also called 'interdigitation' in
reference to the simile of fingers of opposite hands interlaced, as if
in prayer. It is much harder to separate hands with interlaced fingers
than when the hands simply lay one on the other."

"When rubber cement is used to bond rubber to itself, the solvent in
the cement swells the substrates somewhat and facilitates the
interdigitation process. After the solvent evaporates, it is hard to
distinguish just where the joint lies. The bonding force is not a
chemical bond -- no bonds are made or broken; the strength of the bond
is purely a physical phenomenon involving van der Walls and London
forces between two intimately mixed and chemically similar non-polar
hydrocarbon rubber molecules."
http://www.madsci.org/posts/archives...3004.Ch.r.html
Thanks, Carl. I'm now edified. I have for a long time
noted how patches seem to be either pulled or pushed
onto the surfaces to which they're adhered, and I've
casually wondered about whatever processes might be
at work, but I've never actually gotten around to
verbially articulating my puzzlement. Now I'm wondering
how those long polymers find their ways into their holes
or ruts or whatever allows them to interdigitate -- do
they just fall in when a hole opens up beneath them,
or do they just randomly flow around until they drop
into a hole/rut/whatever? If they're electrically drawn
in, could that arguably be a chemical process?

I am nevertheless still mystified by how a properly
applied patch seems to be either pushed or pulled
into place, as if an invisible thumb had been pressing
on it all night long. The patch doesn't just lie there
like a fillet of sole or a postage stamp -- some force
has snuggled it intimately right up to the inner tube,
as if patch & tube are spooning. If it's those long
polymer thingies, they must act like an octopus's
tentacles drawing its prey to its beak. But to the
best of my limited knlowledge, molecules don't possess
volition.

I guess the clue lies in whatever keeps an improperly
applied patch from working.

But I have another poser for you, if you're inclined to
spend even more time in response: what does so-called
"vulcanizing" rubber cement do, that non-vulcanizing
rubber cement doesn't?

During my more austere days, I found that vulcanizing
rubber cement works better than non-vulcanizing
rubber cement (or contact cement for that matter) for
minor, external ~tire~ repairs. A swatch of jeans denim
slathered with contact cement makes a fairly usable
internal boot, but you can feel the lump with each
wheel rotation.


cheers,
Tom

Dear Tom,

Rubber cement works by interdigitation, with no chemical changes. It
doesn't vulcanize the rubber pieces, meaning that no cross-links are
formed and no chemical changes occur.

Cold vulcanizing fluid contains chemicals (the "accelerators" below)
that do produce cross-links between the rubber molecules, just as hot
vulcanizing (heat plus sulphur) changes the chemical structure of
rubber.

The wait-until-tacky prescription for cold vulcanizing fluid has a
surprisingly simple explanation:

"Vulcanizing fluid has two primary functions. First, it contains
chemical accelerators which vulcanize the repair to the tire. Second,
when dry, it leaves the prepared surface tacky, which helps hold the
repair in place until vulcanization occurs."
http://www.premaproducts.com/Technic...3c9abed.0.html

Cheers,

Carl Fogel


when do we get the review of loctite 404's effectiveness?