Newsgroup sci.polymers 8381

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The Poisson equation relates the delsquared of the potential p to
the charge density at the point in question.
The Boltzmann distribution law gives the average local concentration 
of particles of charge q at that point as an exponential of (-qp/kT).
Sorry I can't use adequate mathematical symbols here.
Then the net local charge density is worked out as the sum of local
concentration times particle charge for all charged species involved.
The Poisson-Boltzmann equation simply equates these two expressions
for the local charge density.
What Debye and Huckel did was to use the linear approximation to the 
exponential so as to get a manageable solution to the differential 
equation for the potential which resulted.
Robin Stokes.
>Daniel Adamek wrote:
>> 
>> Could anyone point me in the direction of a derivation of the
>> Poisson-Boltzmann equation.
>
>I'm not sure but you migh try "Zeta Potential" by Hunter.  I think he 
>derives all electrostatic equations in the appendices.
>
>Grant
>planetn@nt.net
 resulted.

I would like to find a good polymer that would replace Polyurethane. Also I
would like to know elastomeric polymers with good tensile strength when
incorporated in a compression type of bandage. This is my class assignment
for polymers in Medicine.
Thank a lot ****** Basha:):):):):):):

I need an adhesive that is appropriate for cold bonding the following 
interfaces.
1. silicone to stainless steel
2. silicone to plastic (PBT)
The silicone is approx. Shore Durometer 30 A.
I have already tried epoxy adhesives, acrylic adhesives, and 
cyanoacrylates but I have had no success. The silicone peels easily away 
from the adhesive even after curing.
Does anyone out there know what adhesives will stick to silicone?
Thanks,
Brian

Not long ago there was an automobile engine made out of a manual lay up 
polymer in Canton Ohio.  The Company was intending to develpoe it 
further but no new news on it.  I believe the original article was in 
Plastics Today.  The problem is they did not identify the polymer used. 
I was hoping to find a material that can withstand such stresses and 
temps as an engine block would.  Preferably the material would be able 
to be cast in an open mold and set up without addition of extreme heat 
(baking)  would like to be able to bond it to ceramic or have it resist 
open flame and high temps (5000F) for up to 10 min.
Hope I am not askin for the world, but a supply source would be nice 
too.

To the best of my knowledge, PS has very poor uv stability, ever
leave one of those plastic wine glasses outside?  they get
pretty nasty really fast.  Don't know if it can be stabilized, but
I don't think its easy.
-Bob

Have you considered some of the Metallocene PE's?  they arent too
far off from what you are seeking (I dont think) and are probably
much cheaper and more available than your next alternative.
In article <326FE987.4F75@scigen.co.uk> Julian Scarfe  writes:
>I'm looking for a *high* tear strength elastomer film with a *low*
>force-to-extension ratio up to about 100% elongation.  The thickness can
>be chosen for best compromise between the two.  Ideally, I'd like it to
>be available in both clear and opaque formulations.
>
>Any recommendations for a suitable material please? Is polyurethane
>suitable? SEBS? Or is there some other material better suited to such an
>application? 
>
>Thanks in advance
>-- 
>Julian Scarfe                        jas1@scigen.co.uk
>Scientific Generics                  http://www.generics.co.uk/
>Cambridge CB2 5NH                    Tel: +44-1223-875200
>UK                                   Fax: +44-1223-875201

Brian Land  wrote:
>I need an adhesive that is appropriate for cold bonding the following 
>interfaces.
>1. silicone to stainless steel
>2. silicone to plastic (PBT)
>The silicone is approx. Shore Durometer 30 A.
>I have already tried epoxy adhesives, acrylic adhesives, and 
>cyanoacrylates but I have had no success. The silicone peels easily away 
>from the adhesive even after curing.
>Does anyone out there know what adhesives will stick to silicone?
>Thanks,
>Brian
Try RTV silicone based adhesives available from the silicone elastomer
manufacturers such as Dow Corning, GE Silicones, Wacker.  Any
distributor of adhesives / sealants should be able to supply small
quantities for you to try.
These will bond well to the silicone but you will need to be careful
in the selection of product and in preparation and priming of the
surface to get best results for each surface you want to bond to.  The
manufacturers will be able to offer technical advice.
Alan Randle

In article <01bbc2ad$827bc1e0$ec529ecf@cyberramp.net.cyberramp.net>, 
fowler@cyberramp.net says...
>
>I would like to find a good polymer that would replace Polyurethane. A
>would like to know elastomeric polymers with good tensile strength whe
>incorporated in a compression type of bandage. This is my class assign
>ment for polymers in Medicine.
>Thank a lot ****** Basha:):):):):):):
   Look into the Atochem pebax grades of polymers.  There are grades I have 
used that come close to TPE.
-- 
---------------------------------------------------------
Lawrence Alpert    FLUORTEK, INC.     610-559-9000 voice
Prod. Dev. Eng.    12 McFadden Rd.    610-559-1919 fax
larryal@enter.net  Easton, PA 18045
Custom Medical Extrusions, Compounds, and Assemblies

Re: Remolding expanded polystyrene
> Hi.  Being new to this group I may have missed previous discussions, but I'd 
> like some help with the following; the reference books I've seen haven't been
> much help (the names of relevant references would also be appreciated).
> I'm trying to determine the best method for re-molding expanded polystyrene. 
> Some compaction (say less than 50%) of the material would be acceptable.  The
> most likely pre-processing I envision will be washing and mechanical  sizing 
> of the material.  After that I'm unclear as to:
> 1) will heat/pressure alone allow for remolding, and if so, at what 
> conditions will bonds form?  (I'm not sure what tensile strength I'll need)
> 2) is some form of binder required?  Under what conditions should it be 
> applied?
> 3) is a mold pre-prep required to give a smooth, non-porous finish?  
> 4) are there any companies currently doing this sort of thing?
> 5) is it easier to just reprocess to impregnated PS beads?
> Thanks in advance for any assistance offered.  You can e-mail me direct at
I wonder are you looking for 100% reuse (no virgin mix).
Where I work we use about 10% regind (depending on amount of rejected parts)
for most all materials we injection mold. (clear lexan and plexiglass are
not reused except for purging)
I have seen polystyrene remolded 100% regrind it tends to burn.
also the blowing agent tends to work twice (not as much pe-20 needed the
second time round).
Douglas Connor
Molder/Molding QA

I am looking for information on polymers that have a broad range of
degradation resistance.  Chemicals of interest are acetone, carbon
disulfide, methylene chloride, ethyl acetate, toluene, and 
tetrahydrofuran.  Any information on polymers or polymer treatments
resulting in greater degradation resistance to these chemicals would
be greatly appreciated.
Thanks!
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