Investigation of not fully stable fluids by the method of controlled pulse heating. 2. Short-term thermal stability of polymethyl metacrylate

• Fast-acting technique of implanted probe shock heating was developed.
• Polymer behavior in the region of thermally unstable states was tracked.
• Time–temperature values corresponding to the thermal decomposition onset were found.

The short-time thermal stability of glassy PMMA (polymethyl metacrylate) under conditions of high-power local heating has been studied experimentally. For this purpose, a peculiar procedure in the framework of the method of controlled pulse heating of implantable probe has been developed. The procedure is based on combining the thermal shock and monitoring heating functions with characteristic pulse lengths of the order of 1 μs and 1 ms, respectively. The value of the characteristic probe temperature T*pk was determined, a reproduction of which in a series of measurements under identical parameters of heating function resulted in irreversible changes in the thermal resistance of a polymeric sample. The depth of penetration into the region of thermal instability of polymer (T*pk − Td), where Td is the onset temperature of thermal decomposition in quasi-static process, attains a few hundreds of degrees.