2. Main spinning processes

There are two main classes of process:

• the process of spinning from the molten state (melt spining): in the following text, we will often use an adaptation of this English expression, referring to "melt spinning";

• the spinning process from a concentrated solution, more or less derived from the old viscose process.

The first process is by far the most widely used, as it is much less expensive (and avoids the use of often-polluting solvents), but it can only be applied to polymers with a fairly well-defined melting point, and which do not undergo secondary reactions (such as cross-linking) under the action of heat. The latter is used whenever the former is inapplicable.

Melt spinning is used to spin polyethylene glycol terephthalate (PET, commonly...