Method for improving thermal stability of polypropylene carbonate

Provided is a method for improving thermal stability of polypropylene carbonate and, more particularly, a method of end capping a molecular chain of polypropylene carbonate using a urethane group by adding isocyanates or diisocyanates to a polypropylene carbonate resin, which may optionally be a mixture containing tertiary polyol, so as to delay thermal degradation of the polypropylene carbonate at a high temperature, thereby securing desired thermal stability. Especially, the method capable of being easily applied to reactive extrusion after preparing the polypropylene carbonate has been proposed, thus simplifying production processes and ensuring economical advantages. Moreover, the above method does not deteriorate transparency and specific smoke density characteristics at combustion, which are advantages of the polypropylene carbonate.