thermal polymerization of AA

Could anybody tell me how to do thermal polymerization AA (acrylic acid). The initiator, other additives (preferably biocompatible) and the conditions like temperature, timing, etc for the same.

I tried acrylic acid with benzoyl peroxide (initiator)and PEG and Aerosil for thickening the same (tried with different values of accelerator and at different temperatures like 45, 50, 90 C). As finally I need to have thick layer of the polymer. But this cracks or polymer might be vaporising in the oven. So no results with this.

Also using photoiniator DMPA is also not working. here also the final solution cracks when exposed.

I want to have a uniform n homogenous polymer, which could be spincoated. So any suggestions or solutions are welcome.

Reply to
Sumi
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It seems like you are doing a bulk polymerization (no solvent, and not an emulsion or suspension). If so, cracking will be fairly common. Since you will be spin coating, the cracks should not be an issue.

I would suggest spin coating some of your samples. If that doesn't work, post again with what happened and the group will have some more suggestions (alternate initiators, chain-transfer agents, ...)

John

Reply to
john.spevacek

I have tried to polymerize a very thin layer of my polymer, when treated thermally it cracks. So how could I spin coat if the thin layer I am trying to polymerise is cracking when thermally treated. Some more concrete information is required.

thanks

Reply to
Sumi

The volume of the finished polymer is less than the volume of the initial monomers + fillers + ... Unless the ENTIRE polymerizing material can freely shrink during the entire polymerization, the stress will build up and can cause cracks.The Aerosil that you are using are additional internal sites that prevent the growing polymer from shrinking uniformly. If the PAA is sticking to the substrate at all, that will also cause stresses --> cracks.

If you take the cracked polymer and put it into solution, all the stresses will be relieved and the material will flow back together.

Try dissolving some of you samples and just spread a thin layer out. Let it dry (oven drying is preferred for faster results, but is not necessary in most cases with thin layers) and see if it still cracks.

John

Reply to
john.spevacek

I'm a little confused. Are you seeing the cracks after the intial formation of polymer or is it when you try casting it? It would help if you gave more details on the process and apparatus. Max

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Reply to
cyano8

I am applying liquid mixture onto the copper plate and then trying to polymerise it thermally by putting in the oven. I am seeing cracked solid parts on the copper plate rather than uniform layer of the polymer (which is what required).

I think the thermal poymerisation of the AA is very violent and so am using hydroquinone as inhibitor. But still I am not able to find the right amount of accelerator and the inhibitor to be mixed in the AA+BPO (Benzoyl peroxide) solution. And also the temperature and timing for the polymerisation.

With some certain ratios of accelerator and inhibitor, I was able to see some polymerisation but that also explodes into cracked solid, when I let it remain in the oven for some more time (temp was 40 deg C).

Help me out to get some right solution for this problem.

Reply to
Sumi

An inhibitor will not slow down the reaction once it starts to go, it merely delays the time for the reaction to start. Simplistically, the initiator reacts with the inhibitor and chews it up. Once the inhibitor is gone, the reaction then starts.

Can you make the PAA elsewhere and then coat the copper later? It would be an easy operation to do. But I also notice that your initial post said that you wanted to spincoat the material. Have you given up on that option?

John Aspen Research, -

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Reply to
john.spevacek

Sure it does. The photoreactivity of a low Mw species like AA is huge. Mechanical shrinkage of a UV system is nearly an order of magnitude greater than a thermal equivalent, as the photoreaction timeframe allows for near-zero stress relief during polymerization. A true UV system would be slightly more involed, from a formulating standpoint (oligomer, monomer(s), PI, additives), but is feasible for the system you describe (in so far as you've described it). Are you adverse to a full-blown UV formulation? If not...

What are the final properties of interest to the coating? (desired properties of the liquid formulation, target coating thickness, and salient needs of the fininshed coating; hardness, abrasion resistance, weathering, etc) What is your UV lamp source/setup? (System manufacturer, bulb power rating, bulb size and type (MPMV, Fe or Ga -doped, etc), conveyor speed range or typical flood expose time... dosage and peak irradiance, along with apparatus of measurement would be nice, if you have it.) How much monthly consumption of formulation? Dare I ask... target cost?

With this info, I'd be happy to post a 'paper and pencil' starting point formulation...

Regards, R. David Zopf Bomar Specialties Co.

Reply to
David Zopf

Are you sure about the concept of inhibitor you mentioned?

I want the polymer to be sandwiched between the copper plates, so I am going to coat the copper later as well. I am still looking for spin coating the polymer onto the copper plate and then planning to grow the other copper plate later. That means some sort of lithography on the polymer for my design. I don't know if that is feasible or not. And if yes, then what materials for the processes and conditions are required. I am going to work on that later.

Now I think the picture must be clear. So any alternative approaches or how to practically achieve what I have mentioned above.

Also has anybody done the controlled thermal polymerisation of AA.

thanks...

Reply to
Sumi

I tried with the UV system used as exposure machine in PCB designing, but it seems that just make the monomer to evaporate. Cracks were also there in the final solid material (whatever it was- should be polymer but not sure, can also be just Aerosil). I could give you the details you asked. But would the polymer formed by your formulation, be able to withstand 120 deg C temperature (the temperature used for photoresist stripping in the final process flow).

So thats why I am looking for thermal polymerisation. But if you still think the formulation you are going to give would work, then I could try to give the details you asked.

BRs

Reply to
Sumi

Something like a Karl Suss (or other brand) mask aligner? Yeah, a low intensity flood lamp can volatilize low Mw acrylates before successfully initiating cure.

It was probably a fair portion of polymer...

More exotic UV systems (melamine acrylate plus tris-hydroxy isocyanurate triacrylate oligomer systems) can have Tg's as high as 270 degC (DMA, peak tan delta)... 120 shouldn't be a problem. What is the time at temperature on the stripping step, about 15 minutes, or so? Caustic strip bath, or bake and scrape?

Won't hurt to try. I'll keep it simple. If you prefer email; davidz 'at' bomarspecialties 'dot' com. Note, I work for a UV raw material supplier. That means two things, 1; the formulation will comprise at least one product from my company (I have to justify online activity at work somehow ;-) 2. Bomar doesn't sell formulated products. If your problem gets solved, we'll need to find you a formulator, if you aren't willing and/or able to formulate the product yourself. The formulation should be pretty trivial to assemble, though. If you can disperse an Aerosil product adequately into solution, you probably have the equipment needed to formulate anything I'd propose...

Regards, R. David Zopf Tech Applications Bomar Specialties Co.

Reply to
David Zopf

someone PLEASE answer my queries............

Reply to
Sumi

SOMEONE PLEASE ANSWER MY QUERIES............

(:-Ö-:)

Sumi wrote:

Reply to
Sumi

The volume of posts to sci.polymers might tell you that this newsgroup isn't particularly well traveled. Maybe an X-post to sci.chem would help? Else, find a nearby "brick and mortar" formulating company willing to supply a coating to suit your needs. (Finland, yes? Call BASF Coatings or Wellomer Inc. in Germany, or maybe Marabu.. Hrrm. With your temperature requirement, maybe an electronics coatings co. would be best; Acheson Colloids, German office: +49-7348-20010)

Good Luck!

Regards, R. David Zopf

Reply to
David Zopf

So any suggestions or solutions are welcome.

INFO ABOUT ANY COMPANY WHICH COULD PROVIDE THE POLYMER OF THE ABOVE DESIRED CHARACTERISTICS. I COULD BUY DIRECTLY FROM THEM.

Reply to
Sumi

Hi

Ok, I am interseted in knowing what formulation do you have to solve my problem. I need the final polymer which can be coated and then photolithography can be performed to have my other metal design onto it. So tell me what exactly other things you want me to mention on your work email ID- davidz 'at' bomarspecialties 'dot' com.

BRs Sumit

Reply to
Sumi

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