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I would just love to tell you that many wonderful things are made of polyketones, but I can't. You see, these polymers are so new that not much has been made out of them yet. But polyketones, which are plastics, by the way, have a lot going for them, and we figure it won't be long before a lot of stuff is made from them.
So what's so great about polyketones? Let's find out by taking a look at them. A polyketone is of course a polymer with a ketone group in the backbone chain. The polyketones we're going to talk about on this page are based on the picture you see at the top of the page, where R' is an ethylene linkage, -CH2CH2-. Shell has just put this family of polymers on the market and sells them under the name Carilon. This is not to be confused with a carillon, which is a musical instrument with differently pitched bells, which are often controlled with a piano-like keyboard. Let's see what one of these polymers looks like, next to a chain of good ol' polyethylene for comparison:
It's not much different. The only difference is that the polyketone has those carbonyl groups in it. But those carbonyls do a lot. You see, carbonyl groups are very polar. This is because oxygen is electronegative and draws electrons away from the carbon atom. So oxygen has a slight negative charge and the carbon has a slight positive charge. These polar carbonyl groups are attracted to each other, and very strongly at that. This attraction is so strong that while polyethylene melts at a mere 140oC, the polyketone doesn't melt until 255 oC!
These polyketones have another interesting property. They won't dissolve
in much of anything. To dissolve it you have to use something really
weird like hexafluoroisopropanol. This comes in handy should you want to
make a car part out of this stuff. A car part is no good if it dissolves
when you spill gasoline on it. But that's no problem with polyketones!
This is all very nice, but really, now, what's the big deal? There are lots of high performance plastics out there. There are poly(ether sulfones), poly(phenylene sulfide), polyimides... We've seen high performance before. What makes polyketones so special?
This is what makes polyketones so special. To make polyketones, you take ethylene gas and carbon monoxide, and react them with a palladium(II) catalyst:
Ethylene is dirt cheap; it's the monomer for polyethylene. Carbon monoxide is dirt cheap, too. You make carbon monoxide every time you burn wood, or a candle, or just about anything containing carbon. The reaction is also easy to carry out. Most high performance polymers are difficult to make, because the chemistry has to be just right for the reactions to work. Cheap monomers, and easy chemistry make polyketones rather cheap, a whole lot cheaper than other high performance plastics. In time the price may come down to less than a dollar per pound! This is why we think a lot of stuff is going to be made out of polyketones in the future.
Here's some models of the monomers if you want to play with them. Ethylene is on the left and carbon monoxide is on the right.
One Last DetailThere was a problem with this polyketone when Shell first made it. You see, these polymers are very highly crystalline, that is, the polymer chains are packed together in a very orderly fashion. This makes the polyketones very strong, but the down side is that it also makes them very brittle. the chemists went to work and came up with a solution. They decided to throw a little bit of propylene in with the ethylene and the carbon monoxide when they make the polymer. Propylene reacts just like ethylene does, so we end up with a polymer that looks like this:
Every now and then you get an extra methyl group attached to one of the ethylene units. These methyl groups get in the way when the polymer chains try to pack into crystals. They can still pack, but not as well as before. The bad part is that the melting temperature drops to about 220 oC, because the crystals aren't as strong. But the good part is that the polymer is now a lot tougher and less brittle. This polyketone made with ethylene, carbon monoxide, and a little bit of propylene is the Carilon that you can buy.
Keep watching this page. As soon as we find out what people are making out of polyketones we'll post something here about it!
Reference of this text is: http://www.pslc.ws
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