[dalmatiner]

I keep finding polyurethane described as a polycondensate but also as an addition polymer. I thought that it makes quite a difference whether you say it is formed through polycondensation or polyaddition. I used to explain it like that, that there a two kinds of addition polymerization, the chain polymerization and the polyaddition, whereas the chain polymerization is for alkenes like ethene that break up their double bond to form poylethene etc. and the polyaddition describes a reaction between multifunctional reactants like a polyol and isocyanate that form polyurethane in the end.

Is there a reason why a polyurethane should rather be seen as a polycondensate? Because I read both in two different books that are both quite new and I don't know what to believe now.