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Elmer's Rubber Cement is not the vulcanizing kind!



 
 
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  #61  
Old April 29th 09, 04:55 AM posted to rec.bicycles.misc,rec.bicycles.tech
jim beam[_4_]
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Posts: 318
Default Elmer's Rubber Cement is not the vulcanizing kind!

Still Just Me wrote:
On Tue, 28 Apr 2009 05:48:46 -0700, jim beam
wrote:

you've been told three times now. if you don't get it, you have either
a fundamental education gap somewhere back in junior school, or you're
just too damned dim.


Yeah Tom, Jebus H Christ! What'd you sleep through glue properties
class in 8th grade?


not materials, reading comprehension. like you apparently. moron.
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  #62  
Old April 29th 09, 04:57 AM posted to rec.bicycles.misc,rec.bicycles.tech
jim beam[_4_]
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Posts: 318
Default Elmer's Rubber Cement is not the vulcanizing kind!

Michael Press wrote:
In article ,
(Tom Keats) wrote:

In article ,
Michael Press writes:
In article ,
(Tom Keats) wrote:

In article ,
Michael Press writes:
In article ,
(Tom Keats) wrote:

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?
Physically it is similar to interleaving the pages of
two books.
Interleaving the pages of two books requires thought
and intention and maybe a little cleverness, if the
job is to be done neatly, without collisions.

What forces are at work with this interdigitation/
interleaving? What downright ~makes~ polymers
first agree to interdigitate, and then move around
to align themselves accordingly? Or is this just
another one of those axiomatic things?

Adjacent books don't suddenly decide to interleave
their pages, neither does a jumbled pile of bricks
decide to form a chimney. So I'm having difficulty
with the concept of molecular chains somehow elegantly
and neatly (but non-chemically) organizing themselves
by dint of their proximity to each other.

We're being told one substance somehow molecularly
intimates and intermingles itself with another
similar substance, and yet the process is not
chemical.

BTW, as a preemptive afterthought: Jim Beam and the
horse he rode into town on can both enjoy precious
moments with their respective selves.

Or each other, if they're into that.
The interleaved page analogy is to illustrate
the scale of the forces at work. You did not know that?

^^^^^^^^^^^^^^^^^^

But exactly ~what~ forces are at work?
That is my question.


Induced electric dipole interaction.

We stick a patch on a tube, maybe press it on
a little, leave it overnight, and when we look
at it the next day, the patch is pancaked right
on there as if it had been in a clamp.


The loss of volatile solvent is so rapid you see
the patch move closer to the tube as the glue volume decreases.

I realize the patch isn't chemically integrated
with the inner tube rubber. But it does seem to
be more mechanically squashed onto the tube than
by the thumb pressure that initially installed it
into place. I'm just curious as to what does that.

I'm guessing that as the more volatile stuff in
the cement evaporates, the remaining cement
somehow shrinks, thereby pulling interdigitated
patch & inner tube together. But that's just a
guess on my part, and guessing ain't knowing.
Shrinkage of the cement at least provides an
explanation for the movement necessary for the
process.


Yes.

I think wet newspaper pages are stuck together by
air pressure and maybe a li'l static electricity
largely introduced by foreign material and dust on
the paper. But I'm probably wrong about that, too.
It would be nice to know what's really going on.


Electrical forces are what constitute the London and
van der Waals forces previously mentioned. To know
what is really going on do a year of physics; a year
of chemistry; a year of electrodynamics; a year of
thermodynamics and statistical physics---alternatively
a year of physical chemistry; and a couple years of
calculus. MIT puts all their courses complete with
problem sets on the web.


that's not the point - the point is that it's been explained in this
thread. if you want to get into detail, read up on the above, but you
don't need to do that to simply accept the concept of molecular interaction.
  #63  
Old April 29th 09, 05:22 AM posted to rec.bicycles.misc,rec.bicycles.tech
Nick L Plate
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Posts: 1,114
Default Elmer's Rubber Cement is not the vulcanizing kind!

On 29 Apr, 05:08, wrote:
Trevor Jeffrey wrote:
Remove a well adhered patch. *You will see no indication of
chemical bond formation.
I find a well adhered patch not removable without
heating. *Heating affects the REMA patch orange rubber more than
the tube rubber so they separate with careful pulling. *I have not
cared what remains on the contact surface (it looks clean to me)
before applying a new patch and allowing it to cure.
I have also removed quite a few patches using a suitable solvent -
toluene and xylene are two that work.
The hard part seems to be getting a patch edge lifted to gain
access to the tube/patch interface. *Once that is accomplished the
rest is easy using a slow "peeling" technique in conjunction with
more solvent (think "cotton swab"). *Even well adhered patches will
come off clean leaving no sign that there was ever a patch
adhered/bonded there.
Everyone seems to agree on that last detail.

I cannot support this for I have had no desire to remove a well
adhered patch. *Why?


Assuming the rider followed good patching procedures, but chose to
ride his freshly patched tube whose patch can lift off radially from
the hole, forming the dome I described, without leaking. *Such patches
can become slow leaks but in time become "well adhered", requiring
special means for removal as described.

That is Why!


I'm getting splinters under my nails here.
  #64  
Old April 29th 09, 06:26 AM posted to rec.bicycles.misc,rec.bicycles.tech
jim beam[_4_]
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Posts: 318
Default Elmer's Rubber Cement is not the vulcanizing kind!

wrote:
Trevor Jeffrey wrote:

Remove a well adhered patch. You will see no indication of
chemical bond formation.


I find a well adhered patch not removable without
heating. Heating affects the REMA patch orange rubber more than
the tube rubber so they separate with careful pulling. I have not
cared what remains on the contact surface (it looks clean to me)
before applying a new patch and allowing it to cure.


I have also removed quite a few patches using a suitable solvent -
toluene and xylene are two that work.


The hard part seems to be getting a patch edge lifted to gain
access to the tube/patch interface. Once that is accomplished the
rest is easy using a slow "peeling" technique in conjunction with
more solvent (think "cotton swab"). Even well adhered patches will
come off clean leaving no sign that there was ever a patch
adhered/bonded there.


Everyone seems to agree on that last detail.


I cannot support this for I have had no desire to remove a well
adhered patch. Why?


Assuming the rider followed good patching procedures, but chose to
ride his freshly patched tube whose patch can lift off radially from
the hole, forming the dome I described, without leaking. Such patches
can become slow leaks but in time become "well adhered", requiring
special means for removal as described.

That is Why!


er. jobst, you're contrdicting yourself. one moment you say "the rider
followed good patching procedures", then you say "his freshly patched
tube whose patch can lift off radially from the hole".

if the tube is patched per the manufacturer's procedure, the correct
procedure, patches do not lift. thus, if you experience this problem,
you're not following correct procedure.

did you ever study logic?
  #65  
Old April 30th 09, 05:56 AM posted to rec.bicycles.misc,rec.bicycles.tech
Michael Press
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Posts: 9,202
Default Elmer's Rubber Cement is not the vulcanizing kind!

In article ,
Still Just Me wrote:

On Tue, 28 Apr 2009 11:56:18 -0700, Michael Press
wrote:

Electrical forces are what constitute the London and
van der Waals forces previously mentioned. To know
what is really going on do a year of physics; a year
of chemistry; a year of electrodynamics; a year of
thermodynamics and statistical physics---alternatively
a year of physical chemistry; and a couple years of
calculus. MIT puts all their courses complete with
problem sets on the web.


All of which, as jb noted, are taught in Jr. High.


Indeed, I slept through it.

--
Michael Press
  #66  
Old April 30th 09, 02:03 PM posted to rec.bicycles.misc,rec.bicycles.tech
jim beam[_5_]
external usenet poster
 
Posts: 941
Default Elmer's Rubber Cement is not the vulcanizing kind!

Tom Keats wrote:
In article ,
Phil W Lee phil(at)lee-family(dot)me(dot)uk writes:

We're being told one substance somehow molecularly
intimates and intermingles itself with another
similar substance, and yet the process is not
chemical.

Think of velcro, then reduce in scale to the molecular level.
The preparation with rubber cement can be visualised as the process
which makes the fibres on one side curl up into little hooks.


Aaah, I can visualize that.

Thank you.


cheers,
Tom


thank ****.
  #67  
Old April 30th 09, 02:54 PM posted to rec.bicycles.misc,rec.bicycles.tech
dgk
external usenet poster
 
Posts: 827
Default Elmer's Rubber Cement is not the vulcanizing kind!

On Tue, 28 Apr 2009 21:22:28 -0700 (PDT), Nick L Plate
wrote:

On 29 Apr, 05:08, wrote:
Trevor Jeffrey wrote:
Remove a well adhered patch. *You will see no indication of
chemical bond formation.
I find a well adhered patch not removable without
heating. *Heating affects the REMA patch orange rubber more than
the tube rubber so they separate with careful pulling. *I have not
cared what remains on the contact surface (it looks clean to me)
before applying a new patch and allowing it to cure.
I have also removed quite a few patches using a suitable solvent -
toluene and xylene are two that work.
The hard part seems to be getting a patch edge lifted to gain
access to the tube/patch interface. *Once that is accomplished the
rest is easy using a slow "peeling" technique in conjunction with
more solvent (think "cotton swab"). *Even well adhered patches will
come off clean leaving no sign that there was ever a patch
adhered/bonded there.
Everyone seems to agree on that last detail.
I cannot support this for I have had no desire to remove a well
adhered patch. *Why?


Assuming the rider followed good patching procedures, but chose to
ride his freshly patched tube whose patch can lift off radially from
the hole, forming the dome I described, without leaking. *Such patches
can become slow leaks but in time become "well adhered", requiring
special means for removal as described.

That is Why!


I'm getting splinters under my nails here.


I think it's time to buy a new tube.
  #68  
Old May 4th 09, 03:38 AM 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 ,
Michael Press writes:

I think wet newspaper pages are stuck together by
air pressure and maybe a li'l static electricity
largely introduced by foreign material and dust on
the paper. But I'm probably wrong about that, too.
It would be nice to know what's really going on.


Electrical forces are what constitute the London and
van der Waals forces previously mentioned. To know
what is really going on do a year of physics; a year
of chemistry; a year of electrodynamics; a year of
thermodynamics and statistical physics---alternatively
a year of physical chemistry; and a couple years of
calculus. MIT puts all their courses complete with
problem sets on the web.


Maybe one of these days I'll get a round tuit.
Just need a refresher for the Math (funny, how
quickly that stuff falls outa one's brain when
you don't use it every day.) As for the rest,
I'd just need the books & info. Screw the
accreditation.

All that studying could really put a hurt onto
one's riding time.

So, thank you for your kind patience and
willingness to help people understand stuff.
You are appreciated.


cheers,
Tom

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




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