Some Additives are corrosive in nature. Some additive has limited residence time. They degrade and generate corrosive gases. Such polymers should be considered as material of lower stability and handled very carefully with out exceeding the thermal stability time limit.
Flame retardant grades produce corrosive acids at certain temperature. Therefore, the moulding should be done with out reaching such critical temperature. Percentage utilisation should be such that melt remains stable avoiding critical residence time.