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ABSTRACT:The thermal degradation and flame retardancy of poly(butylene terephthalate) (PBT) were studied with a focus on the effect of phosphorous compounds. Thermogravimetric analysis, pyrolysis/gas chromatography/ mass spectrometry (Py/GC/MS), and elemental analysis were used to analyze the flame retardancy, which were observed by an Underwriters Laboratory UL-94 test and a cone calorimeter. The 50% degradation temperatures of PBT blends with phosphorous compounds were the same as that of neat PBT. Six scission products were assigned by Py/GC/ MS. The burning times of the UL test of several PBT blends were much shorter than that of neat PBT. The relation between flame retardancy and thermal degradation was analyzed with respect to the results of the scission products and the char in burned polymers.

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.

ABSTRACT:The diffusion of additives and the deterioration with the passage of time in polypropylene (PP) were studied by using the UL flaming test and the oxygen index test to measure the flame retardancy. The weight change was also measured. The decreases with the lapse of time were observed for multiple flame retardants. Aliphatic brominated compounds showed the best result for flame retardancy in the initial stage of combustion. The best flame retardants for PP to inhibit the deterioration of flame retardancy with the passage of time were brominated hydrocarbon with more than two aromatic rings connected by a functional group or isocyanurate, and phosphates connected with a branching aliphatic hydrocarbon. The weight of the loss was plotted as a function of aging time and temperature to elucidate why the flame retardancy deteriorated. The apparent diffusion constant depends on the temperature and the rate was expressed with the Arrhenius equation. The concentration of flame retardant in PP was calculated by the constant and the equation at arbitrary time after thermal aging. The relation between the performance and chemical structure of the additives was also discussed.

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