Polymer Cracking
Polymer Cracking
(OP)
I am trying to spin-coat a solution of PMMA (MW=15k) on a elastomeric material, but I find that the polymer cracks. Is there any polymer that wont crack? Or can I add any additive to my polymer to prevent cracking?





RE: Polymer Cracking
You need something with higher elongation at break. There are impact modified acrylics or copolymers, polycarbonate, polyurethanes and polyesters to consider.
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RE: Polymer Cracking
RE: Polymer Cracking
This might be silly, but try your local model aeroplane shop. Cellulose (Nitrate or Butyrate type) is still used, as are some of the more "modern" coatings such as PU or Epoxy.
These give thin, tough coatings.
Cheers
Harry
RE: Polymer Cracking
As mentioned above, you need a polymer with higher elongation to break.
Some ideas. Buy some clear nail polish/varnish and dilute that with nail polish remover (acetone or similar) and try that. Afterall it is made to form durable coatings. Model shops will also sell clear varnishes and you can buy polyurethane varnished and dilute them as well.
There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell
RE: Polymer Cracking
The problem is a little challenging, I would highly appreciate your inputs.
RE: Polymer Cracking
There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell
RE: Polymer Cracking
RE: Polymer Cracking
If you use strong corona treatment or flame treatment on the PDMS you can make the surface turn glassy. Will that do?
There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell
RE: Polymer Cracking
I am corono treating the elastomer for 30 s. that does not help. maybe i can treat it for a longer amount of time.
RE: Polymer Cracking
For a soft, soluble acid resist you could try SBS, such as Kraton D (http://www.kraton.com/)or Styroflex (www.styroflex.com). Acetone should dissolve it.
There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell
RE: Polymer Cracking
A butadiene styrene rubber (MW=38000) did work for my application. One thing is that the polymer is not very resistant to acids. Any idea as to how to improve its chemical inertness without modifying its properties?
RE: Polymer Cracking
One tip is to try the hydrogenated SBS types, that way the double bonds are gone and so the rubber will be more chemically stable (i.e. other Kraton types).
There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell
RE: Polymer Cracking
Btw, the idea of using hydrogenated SBS is great. I was just wondering if they would still retain their ductility.
RE: Polymer Cracking
There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell
RE: Polymer Cracking
Some of the SBR polymers I have tried exhibit the problem of cracking. What makes some polymers crack when they are spin-coated on another elastomer? Is it due to different hardness or Young's modulus? Any help in trying to understand the cracking issue would be highly appreciated.
RE: Polymer Cracking
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.