Could wood ever liquefy?

After a spirited discussion about liquids and solids with our inquisitive 3.5-year-old earlier, MrWhatsit pointed out that an aluminum can is basically made of “frozen” aluminum, and you could think of a plastic milk jug as “frozen” plastic, and so forth. This led him, and subsequently me, to wonder what would happen if you took a piece of wood, put it in a zero-oxygen environment, and kept increasing the heat. What would happen to the piece of wood? Would it liquefy, or what?

There may be some odd high pressure and temperature configuration where wood will liquefy, but not at normal pressures. Water or plastics can liquefy at high temps because the bonds between the molecules break down before the bonds within them, so the individual molecules are then free to slide past one another. Wood is a complex polymer with all sorts of crosslinkings. By the time it gets hot enough to break those crosslinkings and allow the molecules to move relative to one another a lot of the internal bonds will have been ruptured by the heat. Large amounts of the wood will have been turned into gas and what you have left won’t be wood any more.

Wouldn’t (woodn’t huh huh) it would act like butter, i.e. liquefy in stages, getting softer and softer until finally it’s liquid - unlike a “pure” substance like water which sharply changes from solid to liquid?

Wood is made up mostly of cellulose and lignin, both of which are long-chain polymers of simpler molecules. My SWAG is that the bonds between the units of the polymers would disintegrate first, so that the wood would become converted to a powder instead of a liquid.

Isn’t this how they make charcoal? Or does that require some oxygen?

Wood can be considered a fiber reinforced polymer, where lignin is the polymer and cellulose is the fiber. There are also hemicelluloes in there, but in smaller amounts, and which contribute less to the strength of the composite. Lignin is thermoplastic, and will soften with heat, if you’ve ever seen a bentwood rocker you’ve seen the phenomenon. To soften and bend wod boiling water and/or steam is used.

Some wood pulps are made using thermo mechanical or semichemical processes that use heat and mechanical energy to soften and remove the lignin.

The thing with lignin is that is is an amorphous molecule of very high molecular weight, and has no defined melting point. Long befor the wood melted, it would have broken down into non wood molecules, even in an oxygen free environment.

I don’t think so. Charcoal-making is more like distillation than anything else - heating wood to decompose it and drive off the volatile fractions. The only thing you need oxygen for is to burn the volatile fractions and so make the whole process self-sustaining, which is how I believe it’s done in practice.

Yes, it is one way of making charcoal, and no, it doesn’t require oxygen. You can make charcoal quite nicely by heating wood in a large can with a small hole in the lid. The hole is to let the volatile gases out, not to let air in, and you can light the gases at the hole and maintain a flame there until the process is complete. I guess you could also pipe the gas under the can and burn it there to sustain the heat.

Traditional “charcoal burning” involves building a large fire to get the wood up to temperature and then covering it with turf to choke off the oxygen supply. As Malacandra says, you need just enough oxygen getting in to sustain the temperature. If you’ve ever read Swallows and Amazons it has a nice description.

Thanks. :slight_smile: So, is this the answer to the OP? The wood will turn into charcoal, and eventually melt at the melting point of carbon (3800 K)?

Hadn’t thought that far, but I guess it is!

The only downside is that you do not then have a nice crucible-full of molten wood that you can pour into a mould.

On the other hand, you do then have some molten carbon, which in principle you could resolidify into diamond. So now we have the following three-step plan:

  1. Melt wood under vacuum.
  2. ???
  3. Profit!

Yeah, I think wood is a complex enough mixture of organic compounds (mostly cellulose, right?) that it wouldn’t observe usual melting point laws, if only because there would be other heat-dependent chemical reactions that would take place, even in a closed system (ie no outside oxygen) before melting would be close to occuring.

Don’t you also make alcohol by heating wood w/out O[sub]2[/sub]?

Brian

Molten carbon?

Have they ever made this, and what was it like? Can you pour it into moulds? (I assume you can’t get it anywhere near oxygen…)

How much wood could a woodchuck …

:smiley: