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Topic: How to achieve a uniform mix of HETEROGENEOUS compounds?  (Read 9444 times)

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Offline priyoX

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How to achieve a uniform mix of HETEROGENEOUS compounds?
« on: September 04, 2017, 04:19:06 PM »
I have liquid PMMA and a solid powder. I want to disperse the powder particles in the PMMA uniformly into a solid block. So while the PMMA is still in liquid form, I pour in the powder and wait a couple of days for the mixture to air cure. The problem is, the powder particles are settling down to the bottom of the beaker. I stir it for a while, but can't keep stirring it for 2 days because I also need it to cure into a solid block. How do I get a uniform dispersion of this powder into the liquid so it cures with the powder uniformly spread throughout the solidified PMMA?   ???

Any help is super appreciated!!  ;D ;D

Offline wildfyr

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Re: How to achieve a uniform mix of HETEROGENEOUS compounds?
« Reply #1 on: September 05, 2017, 07:22:23 PM »
You dont have liquid PMMA, you a a PMMA solution. How would you feel about doing a polymerization with a crosslinker? Youll have to buy a few relatively cheap, low toxicity chemicals.

Do you work in industry or academia where you can use VWR or Sigma Aldrich?

Offline P

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Re: How to achieve a uniform mix of HETEROGENEOUS compounds?
« Reply #2 on: September 06, 2017, 06:00:42 AM »
yea - as wildfyr suggested, it doesn't air dry/cure it is a polymerisation reaction. Add some free radical or some kind of polymerisation initiator and raise the temp to the activation temp of your initiator. You can alter the speed to which the polymerization comes to completion by increasing or decreasing the initiator concentration. You can control MWs also, but this is beyond what you need.

.   unless we have it wrong and you DO have a solution of PMMA in a solvent. But I would expect that to dry out much faster than a couple of days. You probably need to add an initiator to the monomer to get it to react faster as wildfyr suggests. :-)
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Offline wildfyr

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Re: How to achieve a uniform mix of HETEROGENEOUS compounds?
« Reply #3 on: September 06, 2017, 09:14:55 AM »
I had originally written a long post about how he could purchase methylmethacrylate, divinyl benzene, and an initiator (AIBN or benzoyl peroxide) and to stir that at 70C until it locked up, but it was on his other (double) post and it got locked while writing it, and I gave up.

Offline Arkcon

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Re: How to achieve a uniform mix of HETEROGENEOUS compounds?
« Reply #4 on: September 06, 2017, 09:44:11 AM »
Try to see if its in some sort of edit queue in your browser, in situations like that.
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline P

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Re: How to achieve a uniform mix of HETEROGENEOUS compounds?
« Reply #5 on: September 06, 2017, 09:53:31 AM »
I had originally written a long post about how he could purchase methylmethacrylate, divinyl benzene, and an initiator (AIBN or benzoyl peroxide) and to stir that at 70C until it locked up, but it was on his other (double) post and it got locked while writing it, and I gave up.

I was going to suggest AIBN...   but didn't want to recommend it as it can be explosive I think...   NOT as explosive as benzoyl peroxide though!!   I once had to use a balance in a different lab to weigh some out...  idly, as I was walking to the other lab, whistling a tune and tapping out a beat with my spatula on the tub I looked down at the 'explosion hazard' warning sign on the tub and started to wonder about my own sanity with regard to playing the fricking drums on the container...  I stopped immediately.
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Offline DrCMS

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Re: How to achieve a uniform mix of HETEROGENEOUS compounds?
« Reply #6 on: September 06, 2017, 10:54:31 AM »
AIBN is not a shock sensitive explosive so you would have been fine kicking that tub of it back to your lab.  If you warm AIBN up and it gets above its SADT and you do not do anything to stop it it will self heat and might go bang as the pressure build up splits the tub but that would not be a true detonation bang.

Benzoyl Peroxide as a dry solid on the other hand is significantly more dangerous.

Offline P

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Re: How to achieve a uniform mix of HETEROGENEOUS compounds?
« Reply #7 on: September 06, 2017, 11:16:38 AM »
AIBN is not a shock sensitive explosive so you would have been fine kicking that tub of it back to your lab.  If you warm AIBN up and it gets above its SADT and you do not do anything to stop it it will self heat and might go bang as the pressure build up splits the tub but that would not be a true detonation bang.

Benzoyl Peroxide as a dry solid on the other hand is significantly more dangerous.

Yea - I used to use AIBN most of the time, but for the reactions I needed to run on this occasion I need BP...  It was a dry powder.  Still - I don't think tapping a rhythm on the tub would cause it to explode - it would need a bit more force than that...  but exactly HOW much I am not sure...  so I decided to stop what I was doing as soon as I realised it.

A pal started a fire in the fume cupboard once by messing about with the stuff...  he was getting single crystals and bashing them with a spoon to make them explode...  all good fun until a solvent wet cloth that was nearby went up in flames...   He quickly put it out though.  ::)
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Offline DrCMS

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Re: How to achieve a uniform mix of HETEROGENEOUS compounds?
« Reply #8 on: September 06, 2017, 11:42:48 AM »
For a good lesson in how not to deal with dry BP read this - http://www.csb.gov/assets/1/19/Catalyst_Report.pdf

Offline wildfyr

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Re: How to achieve a uniform mix of HETEROGENEOUS compounds?
« Reply #9 on: September 06, 2017, 12:47:54 PM »
Luckily for OP, either he has access to AIBN or his initiator is gonna have to be benzoyl peroxide in the form of 10% in skin cream. I don't know what other initiators are easily available to a consumer.

AIBN is quite safe. I've never felt any particular danger with using benzoyl peroxide. Most polymerizations are fine with using it wet and safe. I think we had the 50% paste, which is borderline edible. The 98% pure stuff would make me raise my eyebrows if I was using more than a few grams.

Offline priyoX

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Re: How to achieve a uniform mix of HETEROGENEOUS compounds?
« Reply #10 on: September 06, 2017, 05:30:34 PM »
You dont have liquid PMMA, you a a PMMA solution. How would you feel about doing a polymerization with a crosslinker? Youll have to buy a few relatively cheap, low toxicity chemicals.

Do you work in industry or academia where you can use VWR or Sigma Aldrich?

I do have access to Sigma Aldrich. What kind of a crosslinker would be a good idea?

Offline wildfyr

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Re: How to achieve a uniform mix of HETEROGENEOUS compounds?
« Reply #11 on: September 06, 2017, 06:06:42 PM »
Either di(ethylene glycol) dimethacrylate or divinyl benzene. Add it in a weight ratio of 90% methylmethacrylate, 8% crosslinker, 2% AIBN in an inert atmosphere if possible. Heat up to 70C with stirring. Youll see it start to turn viscous pretty quickly (<1 hour) then it should lock up. Let it go a few more hours after it locks up. Youll probably have to shatter the glass to get your block out.

If you cant do it in inert atmosphere, and cant get it to work in air, come back here I have a backup idea that also only requires a couple cheap chemicals :).

Offline priyoX

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Re: How to achieve a uniform mix of HETEROGENEOUS compounds?
« Reply #12 on: September 07, 2017, 04:00:18 PM »
Wildfyr, you are awesome. I will try out the crosslinker and AIBN. However, I can't facilitate an inert atmosphere, I do all my experiments in a fume hood. Also, I use a plastic nalgene bucket to pour it in, because it's easier to mill out a polymerised piece out of that instead of glass.

Offline wildfyr

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Re: How to achieve a uniform mix of HETEROGENEOUS compounds?
« Reply #13 on: September 07, 2017, 04:33:26 PM »
Could you cap it with something rubbery and push a nitrogen line on a needle though the cap? Heck even a balloon would do the job in a pinch.

You could do it sealed, but that does make me pretty uncomfortable to heat a volatile liquid like MMA in a sealed container not designed for pressure.

Offline priyoX

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Re: How to achieve a uniform mix of HETEROGENEOUS compounds?
« Reply #14 on: September 07, 2017, 06:04:47 PM »
Also, is it possible to make a composite of the powder and PMMA particles by evaporating a solvent that they both can be dissolved in? What would be a good solvent if this could work??  ??? ???

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