Thermal decomposition products of polyurea?
Here's one abstract:


  The primary fragmentation processes in the thermal decomposition of polymers were studied in detail on a series of structurally related polyureas by direct pyrolysis with a mass spectrometer. Our results indicate that polyureas I–III undergo a quantitative depolycondensation process analogous to that observed for N-monosubstituted polyurethanes. The thermal decomposition of polyureas IV–VI proceeds by intramolecular hydrogen transfer processes that occur at higher temperatures with respect to depolycondensation. Polycarboxypiperazine VI is decomposed by a single-stage decomposition mechanism that leads to fragments with amino end groups and carbon oxide.


I took a look at the article.  Depolycondensation is accurate: most of the polyureas examined decomposed to the "parent" isocyanates and amines.  The temperature range examined was 150&deg;C to 350&deg;C.  

If you're interested in what happens at higher temperatures, I would guess a decomposition to mixtures of CO, ammonia, water, and possibly methane and/or hydrogen.  But I didn't find any references that would support me after a quick look