Frontier9
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Liquid Rubber/Latex
When commercially available liquid rubbers such as PERFORMIX PLASTI DIP & MEHRON LIQUID LATEX are applied to a surface, they
solidify and are flexible. Is the mechanism that causes these substances to solidify simply the evaporation of the solvent that they are in or is
there another mechanism that causes them to solidify? Also, what is/are the solvent(s) that they are disolved in?
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neutrino
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Try to find an MSDS for one of these rubbers. It should list the components.
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Mr. Wizard
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I'm not sure of the mechanism of the Performix Plasti Dip (tool handles?), but the latex they sell for carpets and the older latex rubber solutions
depend upon ammonia dissolved in water to keep the latex suspended. As the water evaporates it loses the ammonia and the latex precipitates out. Some
earlier brands of "Latex" brand water based paints used to carry a very generous amount of ammonia to keep them liquid. Using a couple of gallons of
it in a small room without good ventilation gave me stinging eyes, a burned nose , and a nosebleed. I can hardly smell ammonia, as a result.
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chemoleo
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Yes, ammonia and evaporation of it is the key.
The latex is already pre-vulcanised (polymers are crosslinked to form a 3D matrix).
According to Wiki, Latex is not a defined chemical:
| Quote: | | Latex, as found in nature, is the milky sap of many plants that coagulates on exposure to air. It is a complex emulsion in which proteins, alkaloids,
starches, sugars, oils, tannins, resins and gums are found. In most plants latex is white, but some have yellow, orange, or scarlet latex.
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However there are synthetic variants, but I am not sure they have any chemical resemblance to natural latex.
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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Mr. Wizard
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The main component of rubber is isoprene polymers:
http://en.wikipedia.org/wiki/Isoprene
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chemoleo
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Latex is distinct from rubber as far as I know....
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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Mr. Wizard
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I know they are different, I just thought rubber was a more 'polymerized' version. I must confess my ignorance as to the exact difference. Can you
explain it to me (us)? I know that vulcanized rubber has lampblack and sulfur and much more cross-linking.
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chemoleo
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Well, it seems the definition is indeed diffuse. Wiki and other sites aren't terribly clear.
According to http://www.gloves.com.my/vulcanization.htm :
| Quote: | Latex, in this case, natural rubber latex (from the Hevea Brasiliensis tree that originated from Brazil) is made up of an ultra-fine emulsion of
rubber particles suspended in aqueous (watery) phase. It is very much like milk or blood, if you need a comparison. The aqueous phase, called serum,
contains several non-rubber matters such as carbohydrates, proteins, lipids, minerals, micro-organisms and of course, water. The rubber phase is made
up of billions of rubber globules or particles. Each of these particles contains pure rubber surrounded by a layer of soapy-like substances that keep
the particles apart. The manner this is done is through the negative electric charge on the surface of the particles, so that the particles repel each
other and remain separate. These soapy-like substances are made up of proteins and phospholipids.
Making Natural Latex Useable
The natural latex direct from the trees besides being too watery for use also contains a significant amount of non-rubber and is not a commercially
acceptable raw material. The process of centrifugation concentrates the rubber particles and at the same time removes about two-thirds of the
non-rubber from the serum and the particle surface. Some artificial soap is added to compensate for the loss of the natural soap to prevent premature
coagulation of the latex. Centrifuged latex is the basic material for the manufacture of latex gloves. However, without the necessary vulcanizing
chemicals, the latex will not have the elasticity and strength of making the gloves stretch and not tear.
Understanding Vulcanization
To begin to understand vulcanization, remember that rubber molecule is a very long thread polymer made up of millions of monomer units called
isoprene. The chemical name of natural rubber is therefore polyisoprene, or more accurately, cis 1,4 polyisoprene. Some of these polymer are longer
than others but they are all thread-like and together, still does not have any 'network' strength. Imagine these molecules as cut pieces of cotton
threads and when they are pulled they just fall apart. This is the situation with dry film of unvulcanized latex. |
From http://en.wikipedia.org/wiki/Rubber
| Quote: | | The major commercial source of natural latex used to create rubber is the Para rubber tree, Hevea brasiliensis (Euphorbiaceae). This is largely
because it responds to wounding by producing more latex. |
So from latex rubber is made?
Ammonia is needed because it is basic, btw, which keeps the rubber particles apart, and because it happily evaporates.
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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lordmagnus
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Rubber and plastic
I believe the tool handle dip is liquid vinyl with NAPTHA as a solvent/thinner.
VULCANIZED RUBBER! Mr. Spocks preffered form of contraception. 
I\'ll kill a man in a fair fight, or if I think he is gonna start a fair fight, or if he\'s bothrn me allot, or if I am getin payed good, or probably
over a good woman.
-Jayne Cobb (Serenity) |
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franklyn
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Any thoughts on this ?
How does one restore , recondition and rejuvenate an item made of rubber
that has deteriorated to the point that it breaks and crumbles ? Conventionally
this is not even attempted only replaced with a remanufactured part.
Conservation appears to be a work in progress and highly specialized.
http://www.conservation-us.org/index.cfm?fuseaction=page.vie...
Commercial preparations and treatment typically only address the cosmetic
appearance to reverse and prevent surface hardening and cracking.
Online research yielded some old folk remedies such as found in Henley's formulary.
Soaking and treatment with Glycols such as Glycerin and Ethylene Glycol in the
form of automotive antifreeze or even polyether polyols is mentioned , such as
Brake fluid or Transmission stop leak additive to regain flexibility.
Of course the exact type of rubber compound will matter but common rubber as
the type used for snubbers , bumpers and feet , Butyl or Neoprene is what I'm
refering to.
http://www.pslc.ws/mactest/pb.htm , http://www.pslc.ws/mactest/elas.htm
Chlorinated solvents such as Trichloromethane , Dichlormethane , Trichloroethylene
and aromatics as Toluene , and particularly Carbon Disulfide , all seem likely solvents.
http://www.tasco-safety.com/workgloves/chem.html
http://www.des.umd.edu/ls/gloves.html
Possible approach to repair briefly speculated here _ http://www.pslc.ws/mactest/tpe.htm
I'm thinking that soaking in a solvent will soften the material some but the real
question is how to remedy the oxidation that has broken down the polymer ?
Under vacuum the material can be permeated with some additive and then
heated in a microwave to again promote polymerization. Any thoughts on this ?
Related thread _ http://www.sciencemadness.org/talk/viewthread.php?tid=4999
.
[Edited on 12-6-2010 by franklyn]
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