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Elmer's Rubber Cement is not the vulcanizing kind!



 
 
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  #1  
Old April 25th 09, 02:02 AM posted to rec.bicycles.misc
Ablang
external usenet poster
 
Posts: 128
Default Elmer's Rubber Cement is not the vulcanizing kind!

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?
Ads
  #2  
Old April 25th 09, 02:33 AM posted to rec.bicycles.misc
Tom Sherman[_3_]
external usenet poster
 
Posts: 425
Default Elmer's Rubber Cement is not the vulcanizing kind!

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.

--
Tom Sherman - 42.435731,-83.985007
LOCAL CACTUS EATS CYCLIST - datakoll
  #3  
Old April 25th 09, 04:58 AM posted to rec.bicycles.misc,rec.bicycles.tech
Tom Keats
external usenet poster
 
Posts: 100
Default Elmer's Rubber Cement is not the vulcanizing kind!

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
  #4  
Old April 25th 09, 06:50 AM posted to rec.bicycles.misc,rec.bicycles.tech
[email protected]
external usenet poster
 
Posts: 7,934
Default Elmer's Rubber Cement is not the vulcanizing kind!

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

Cheers,

Carl Fogel
  #5  
Old April 25th 09, 02:16 PM posted to rec.bicycles.misc,rec.bicycles.tech
jim beam[_4_]
external usenet poster
 
Posts: 318
Default Elmer's Rubber Cement is not the vulcanizing kind!

wrote:
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

Cheers,

Carl Fogel



thank you. how many more times we have to hash this through tough
remains to be seen.
  #6  
Old April 25th 09, 02:41 PM posted to rec.bicycles.misc,rec.bicycles.tech
jim beam[_4_]
external usenet poster
 
Posts: 318
Default Elmer's Rubber Cement is not the vulcanizing kind!

jim beam wrote:
wrote:
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

Cheers,

Carl Fogel



thank you. how many more times we have to hash this through tough


spelling: "though"


remains to be seen.

  #7  
Old April 25th 09, 06:14 PM posted to rec.bicycles.misc,rec.bicycles.tech
Tom Keats
external usenet poster
 
Posts: 3,193
Default Elmer's Rubber Cement is not the vulcanizing kind!

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

--
Nothing is safe from me.
I'm really at:
tkeats curlicue vcn dot bc dot ca
  #8  
Old April 25th 09, 11:56 PM posted to rec.bicycles.misc
Peter Cole[_2_]
external usenet poster
 
Posts: 4,572
Default Elmer's Rubber Cement is not the vulcanizing kind!

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 never had any luck with it either.
  #9  
Old April 26th 09, 03:24 AM posted to rec.bicycles.misc,rec.bicycles.tech
Nick L Plate
external usenet poster
 
Posts: 1,114
Default Elmer's Rubber Cement is not the vulcanizing kind!

On 25 Apr, 18:14, (Tom Keats) wrote:
In article ,
* * * * writes:



On Fri, 24 Apr 2009 20:58:24 -0700, (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.


It is surface tension which works with an impact contact adhesive, but
it has poor shear strength because it is a long chain non-locked
polymer. It acts like a fluid under constant stress and will tear
apart in time. You need to use a crystalline setting adhesive to
negate the shear problems you are encountering. I've never bothered
to use more adhesive than required to locate the boot after I found
normal contact adhesive does not hold up for long. Useful on the day,
but not for permanent repair. Always use butyl tubes after a
significant boot repair when using normal contact. Always use the
thinnest coat that you can put on both pieces and press together with
an almighty force (once solvent has evaporated), excluding air pockets
at all costs.
  #10  
Old April 26th 09, 04:45 AM posted to rec.bicycles.misc,rec.bicycles.tech
Nick L Plate
external usenet poster
 
Posts: 1,114
Default Elmer's Rubber Cement is not the vulcanizing kind!

On 25 Apr, 18:14, (Tom Keats) wrote:
In article ,
* * * * writes:



On Fri, 24 Apr 2009 20:58:24 -0700, (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


.... and clean the tube with spirit, then heat the tube before applying
cement by rubbing with the handle of a teaspoon. Spread the cement as
thin as possible with the handle of a cold teaspoon. Always used to
use spoons for puncture repair, but couldn't remember quite why until
I did some tub repairs today. I could only remember using the spoons
as tyre levers. Thirty years later, I now remember there was further
uses for spoons that tyre levers do not satisfy. For four years I
used a bike that was a bit big, so not that much and no punctures
because I wouldn't ride it in the rain with it being too big for me.
It was in this period I forgot how to make a most effective repair.
The bike was transport for baseball games/practice and table tennis
at other times. I couldn't enjoy a distant ride on a large bike.
 




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