And would it be possible to melt wood into a puddle in the right conditions?
In: Chemistry
The fact that wood doesn’t melt has to do with it’s particular chemical structure.
Wood is composed of a large number of compounds, but by far the most abundant is cellulose which is a carbohydrate.
Cellulose is in turn composed of extremely long chains of glucose sugars chemically bonded to each other, like a string of beads. There may be tens of thousands of individual glucose units. In chemistry this is known as a Polymer.
You can break cellulose down into individual glucose sugars. There are a number of methods you can use to do this. This is how many fungi get their energy, by digesting wood into simple sugars.
Pure glucose itself melts easily, and is used as an ingredient in candies.
In order to form a liquid, molecules need to be able to easily slide and bump past each other.
This can’t happen with the glucose molecules bound in long chains. Not only that, but the glucose chains are organized into a repeating crystal structure where they fit together like bricks in a brick wall.
Even if one individual glucose molecule is free to wiggle around a little without being unduly attracted by it’s neighbors and jump into a liquid state it’s still restrained at both ends. And this tends to cause it’s inertia to be transferred back down the chain. Those ends are anchored to thousands of other nearby glucose units. The attractive force between adjacent glucose units is much weaker than the chemical bonds linking the glucose chains together. However because the chains are so long and well ordered this keeps any individual glucose molecules from moving out of position.
Therefore wood itself begins to chemically break down, decompose and char well before it will melt. What this really means is that on the whole the force holding the cellulose chains in the solid crystalline matrix is as strong as the chemical bonds in the glucose subunit itself.
This is also true in certain synthetic polymers, depending on their structure. One example is the resin used in heat shields on spacecraft.
However with man-made polymers it’s usually desirable for them to be able to melt, or at least soften to a taffy-like state. This is usually done by limiting the lengths of the chains to, say 100-200 units. This allows them to melt with some effort, but without chemically breaking down. This allows them to be molded into shape easily, or sun and drawn into fibers.
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