Making rubber stiff
Peter D. Lauren
not rigid but not very malleable either. I know this seems like a strange
request but I would ideally like to find something which I could soak
a small piece of rubber in to reduce its flexibility (preferably in a
reasonably controlled way).
Thanking you in anticipation,
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%% Peter D. Lauren, %%
%% ITC Academic Computing - Health Sciences, %%
%% University of Virginia. %%
James H G Owen
>I was wondering if anyone could tell be the best way to make rubber stiff,
>not rigid but not very malleable either. I know this seems like a strange
>request but I would ideally like to find something which I could soak
>a small piece of rubber in to reduce its flexibility (preferably in a
>reasonably controlled way).
>
is proportional to temperature. Cool it down and it will be stiffer. Warm it
up again and it will be malleable.
c.f. the Richard Feynman experiment to show why Challenger blew up.
James
Antoni S. Gozdz 21131
I don't think that's what the original poster had in mind. Two methods
come to mind to increase the rigidity of a finished rubber product
(well, what is this 'rubber' made of? There are many varieties of
elastomers that the general public would call rubber, and the
method to increase its stiffness will depend on the chemical
composition.) To wit:
1. crosskinking by ionizing radiation (electron beam in the MeV
range, like the one used to sterilize medical supplies)
2. intermesh (co)polymerization: swell the 'rubber' product on a
mandrel in a monomer mixture containing an alkyl acrylate and one of
the following: alkyl methacrylate, styrene, acrylonitrile,..., and
0.5-1 % of a free-radical polymerization initiator, like benzoyl
peroxide, azo bis(isobutyronitrile) (AIBN) etc. Wipe out the excess of
the monomers (they are toxic!!!) and place the swollen 'rubber' product
in an airtight polypropylene or Mylar bag (not polyethylene!) in
an air oven at 60oC for 10-15 h to polymerize the more rigid
stuff in the elastomeric matrix.
A lot of work would be needed to determine the composition of the
monomer mix and swelling conditions to achieve a desired degree of
rigidity. Compatibility of the two matrices is another question. There
is no way to tell without testing for the residual monomer content etc
etc whether the final thing is acceptable for medical purposes.
It's probably easier to get started with an appropriate
formulation than to midify the rigidity of the finished product.
Tony
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Antoni S. Gozdz
to...@nyquist.bellcore.com
hol...@garnet.berkeley.edu
A way to make rubber stiffen, if I remember correctly, is to rub in
sulfur, maybe with heating (i.e. vulcanization). This is how they make
tire rubber so hard. I'm not sure what proportion to use, though.
Pat
--
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Patrick Holland hol...@garnet.berkeley.edu
Dept. of Chemistry Q: What do you do to an elephant with 3 balls?
U. Cal, Berkeley A: Walk him and pitch to the rhino.
Andy P. Bajorinas
>Tony
If it is real rubber how about heating it (Vulcanization) I THINK this
makes it more rigid.
Jim Oliver
(James H G Owen) wrote :
JO>In article <CnJoG...@murdoch.acc.Virginia.EDU> pd...@galen.med.Virginia.ED
JO>Peter D. Lauren) writes:
JO>>I was wondering if anyone could tell be the best way to make rubber stiff,
JO>>not rigid but not very malleable either. I know this seems like a strange
JO>>request but I would ideally like to find something which I could soak
JO>>a small piece of rubber in to reduce its flexibility (preferably in a
JO>>reasonably controlled way).
JO>>
JO>How about something simple like cold water, iced water. The stiffness of rub
JO>is proportional to temperature. Cool it down and it will be stiffer. Warm it
JO>up again and it will be malleable.
JO>c.f. the Richard Feynman experiment to show why Challenger blew up.
Speaking as a rubber chemist, it is infinately better to make it stiffer
from the start rather than after it's been moulded. Can you do this ?
Soaking rubber in conc sulphuric acid for a 15 mins will give it a hard
layer of very stiff materail which will crack if bent, unfortunately :-)
Jim Oliver <jim.o...@welcom.gen.nz> (3:771/370)
* SLMR 2.1a *
Appleby Austin M
> James
I'm new here, thought I might be able to lend a hand- If I remember
correctly, rubber can be stiffened by adding sulfur compounds (not sure
whether pure sulfur or sulfur dioxide is used though) during manufacture. I
might be in error, but I think this is how hard rubber combs and the soles
of some dress shoes are made.
-Austin Appleby