Effect of crystalline form of flame-retardant on blooming mechanism

The EVA content necessary to suppress the blooming in sheetings was determi ned. The content was higher than that in the case of injection moldings, an d the appropriate blooming acceleration temperature was around WC being hig her than that in the case of injection moldings. This is assumed to be beca use the amorphous region of PP in sheetings which can dissolve TBA-DB is le ss than that in injection moldings and because there exist skin layers wher e the transportation rate of additives is low in injection moldings. When a stimulation is applied to a part of surface of injection molding or sheeti ng by, for example, sucking operation and handling just after processing, a blooming generates at the part, and the necessary EVA content was determin ed to suppress it. TBA-DB has crystalline and amorphous forms, and the crys talline substance was observed as blooms while the transparent amorphous su bstance was not observed. Whether the crystalline substance is formed in th e processed article or not unitarily determines the generation of blooming. When a stimulation was applied to the surface of a processed article at te mperatures above the softening temperature of the amorphous substance (40 d egreesC), crystallization nuclei generated on it. By aging the processed ar ticle at temperatures above 40 degreesC, the nuclei absorbed the amorphous substance, grew and became to be observed as blooms.