Thermal Degradation and Flame Retardancy of Polycarbonate as a Flame Retardant Polymer
Tomoyuki ISHIKAWA, Ikuhiro MAKI, Tomokazu KOSHIZUKA and Kunihiko TAKEDA
Abstract:The thermal degradation and the flame retardancy of polycarbonate (PC) as one of the excellent flame retardant materials have been studied. Decabromodiphenylether (DBDPE), bisphenol-A biscrezel phosphate, red phosphorous, magnesium hydroxide, ammonium polyphosphate/pentaerythrytol and perfluoro-buthane-sulfonic acid potassium salt (PPFBS) were used as flame retardants. TGA and Py-GC-MS were used for analyzing the degradation and the assignment of the scission products. UL-test and cone calorimeter test were applied to observe the flame retardancy. Mg(OH)2 and ammonium polyphosphate (APP) made the molecular weight lower and the flame retardancy worse. It was due to hydrolysis of PC chain. Red phosphorous and PPFBS as well as DBDPE and organic phosphate which have been used as industrial flame retardants restrained the flammability. In particular, a very small amount of PPFBS showed an excellent effect on the flame retardancy measured by UL-test. However, the ignition time of PC blended with PPFBS measured by cone calorimeter was shorter than that of neat-PC. The relation between the flame retardancy and the thermal degradation has been analyzed. The generation of bisphenol-A as a scission product affected on the flame combustion time and the secondary decomposition of bisphenol-A was observed. The different thermal degradation paths were observed and simulated by computer in the case of the blends where the cleavage of isopropylidene in the chain took precedence over the hydrolysis of carbonate and crosslinking reaction was considered to follow the cleavage. The char on the surface was analyzed by elemental analysis and the chemical structure was discussed. Key Words:Flame retardancy, Polymeric materials, Polycarbonate, Thermal degradation, Char