"Definition: Something (A) is relevant to a task (T) if it increases the likelihood of accomplishing the goal" Wiki.

So, "the process of making polyurethane foam" is relevant to polyurethane foam in that it allows it to be created.

One way to make polyurethane foam is by mixing the two constituent chemicals together and pumping the mixture immediately through a spray nozzle. Like spray paint, the foam can be applied to a surface in successive layers. The reaction between the two components generates vapor that froths the mixture into closed-cell foam, which is a good insulator as well as having low permeability to water vapor.

The chemical reaction is exothermic, and thus the foam is hot until it cures. Thus the chemistry is relevant. If sprayed on in too thick a layer, it can even ignite. After curing, if the foam is exposed to fire, it will burn, releasing noxious gases. Thus it should be covered with fire-resistant material so that stray sparks won't hit it, for instance. There are fire-resistant paints for this purpose, or the foam can be covered with other construction materials.

The vapors are also noxious as the foam is being generated, so the person doing this needs to be protected with an air-supplied hood or equivalent means, and other persons must be prevented from entering the area until the foam is sufficiently cured.

This is just the briefest of summaries; the chemistry is important throughout.