What Polymer Did I Obtain?

[Enthalpy]

Hello nice people!

 

As a teenager I once obtained a polymer... But which one?

 

I had dry NaOH in a test tube as d=1mm balls, plus some Aluminium balls, both coming directly from a household product sold to clean toilet flows.

I poured Cl₃C-CH₃ (1,1,1-trichloroethane sold as thinner for tipp-ex) on them. All at room pressure and temperature, and under the best teenager practices of unknown purity, uncontrolled proportions and approximate cleanliness.

 

An emulsion formed and buoyed to the surface where it formed a solid stopper, about 1/3 the volume of trichloroethane (maybe limited by the available NaOH). I had to break the test tube to get the stopper.

 

When breaking the test tube, it smelled like trichloroethane, and I didn't notice odours like hypochlorite (which I recognize in water!) nor chlorine. The reaction hadn't evolved gas neither.

 

The polymer (I suppose it was) looked compact, it was white, softer than polypropylene but much harder than wax, EPDM or glue for hot glue gun - about as soft as polymethylpentene. Its density could match a polyolefine, but I had no means to measure it.

 

It burned like a polyolefin, with the faint smoke and typical flame and odour. An odour very different from to polymers containing oxygen like POM or chlorine like PVC. A quiet flame and faint smoke very different from multiple-bonds polymer like unloaded latex or polybutadiene.

 

A tridimensional network of C-CH₃ would have an amount of hydrogen compatible with the reactants, but I'd expect it (wrongly?) to be a soft elastomer.

 

Can you suggest what it was? Thank you!

Marc Schaefer, aka Enthalpy

[Ronald Hyde]

Tridimensional networks are hard. That's how they cure rubber, cross linking linear polymers. And epoxy too.

[Enthalpy]

OK. Some 3D linked polymers are hard, like hard rubber. So from its hardness, the thing I obtained could be cross-linked.

Though, I believe to remember that when burning, it melted like a polyolefine does, while I imagine heavily cross-linked polymers are thermosetting ones only.

 

What could the thing have been?

[Enthalpy]

Was the polymer oxygen-free? I doubt now. Hot glue guns melt a copolymer with PVA and it smells paraffinic, so maybe there were oxygen atoms in the links.

 

Could it have any use? Polymer designers are happy when they obtain a strong and stiff fibre that resists heat, but when I'm a mechanical designer I need more varied properties depending on the use: very low density, high or low gas permeance, high volume compressibility, big or small rebound, big deformation and shock absorption... I'm sure many lab creations were abandoned that would have met specific uses.

[John Cuthber]

One possibility would be removal of HCl from the trike to make 1,1 dichloroethane, followed by polymerisation to

PVDC

http://en.wikipedia.org/wiki/Polyvinylidene_chloride

 

Probably a mixture of products.

[Enthalpy]

http://msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_005d/0901b8038005d707.pdf?filepath=plastics_eur/pdfs/noreg/190-00347.pdf&fromPage=GetDoc

"Vinylidene chloride Cl₂C=CH₂ is prepared commercially by the dehydrochlorination of 1,1,2-trichloroethane with lime or caustic in slight excess"

Looks alike!

 

Though, I wonder about the flame and its smell. At least PVC burns instably and produces black smoke and a pungent odour - I extrapolate it to PVDC. The polymer I got burned easily, without smoke, and the odour was wax-like.

Same Pdf, on page 917: smoke, ignition resistance...

 

PVDC (properly obtained, compact, pure!) has a density of 1.77 and 1,1,1-trichloroethane 1.32 but the polymer I got buoyed. Commercial PVC can be as light as 1.30 and would be lighter if improperly produced.

[Enthalpy]

Do you see any chance that I got a sort of polyketone, just one -CH₂- shorter than the usual one obtained from CO and C₂H₄? At least the flame's smell was compatible with C, H, O but not with Cl.

Resembling PVDF, maybe the short polyketone is ferroelectric too? It depends on how the chains arrange in the solid and on the temperature. The usual polyketone, with one -CH₂- more, is too symmetric to be ferroelectric.

A ferroelectric material keeps a permanent polarization after the application of a strong electric field. Then, it behaves similarly to a piezoelectric material, or even better in most applications. Uses as memory devices were investigated too.

The short polyketone would avoid fluorine in the production and destruction. And if my teenager tinkering really produced it, then it's facile.

Marc Schaefer, aka Enthalpy

[DrP]

Don't suppose you can give some to someone to run an NMR? That's the best polymer id technique I remember.

I first thought either PVC (for similar reasons stated above) or just polyethylene if the sodium salts out with the chlorine and water in dehydration...  idk . Looking at the physical properties of the polymer though might not help as you do not know how far cross linked it is or what the MW is..  these things can effect the hardness etc.  NMR would tell you straight away (sorry if that doesn't help as you would probably have done this had you had access to one).

[Enthalpy]

Thanks DrP!

PVC and PVDC look reasonable but I'm confident I recognized the odour when I burned the polymer. I smelled like burning paraffin, which polyolefins do and also polymers containing oxygen like hot glue gun. The flame and lack of smoke also hint to chlorine-free material.

NMR: I have a university in the vicinity with a chemistry department. Whether they're interested in my tinkering? At least, reproducing the synthesis would be easy.

[DrP]

I used to have contacts at my old uni who I reckon would have slipped the odd NMR through on the quite for me... I might still be able to wangle that, but they are more likely to charge me £60 nowadays as they know I work in industry. I think I got quoted £30 in the past...  I know they put it up to £60.00, but it could be even higher now....  For something personal and speculative I would try the gift of the gab and see if you can't blag a one off run for free, lol. Worth a try and could be an exercise in charisma....  of which I am sure you have plenty.   Good luck.

 

PS - of course IR spec might be easier and will also give structural info...  It will be cheaper too maybe...  but you don't get much cheaper than free.

Edited October 25, 2017 by DrP

[Enthalpy]

On 10/25/2017 at 0:58 PM, Enthalpy said:

The usual polyketone, with one -CH₂- more, is too symmetric to be ferroelectric.

Failed! The usual polyketone is known to be ferroelectric, pyroelectric, optically nonlinear, etc. From:
Asymmetric Catalysis from a Chinese Perspective, edited by Shengming Ma

That's encouraging. The asymmetric one, with a C₂ chain per period instead of C₃, must be more strongly ferroelectric.

I ignore if producing a polyketone with C₂ chain per period is easy, nor if I did it, so may I suggest to try the polyketone with C₄ chain per period? Less polar but unsymmetrical.

The C₃ chain per period is obtained from carbon monoxide and ethylene or propylene over a catalyst
https://en.wikipedia.org/wiki/Polyketone
so maybe cyclopropane instead of ethylene makes the C₄ chain per period? One process sends the gases on warm solid catalyst, so more heat looks possible. Substituted cyclopropane can make a stiffer polymer chain.

As usual, lamination helps put the macromolecules straight and parallel, drawing or extrusion too.

Marc Schaefer, aka Enthalpy