Brominated polycarbonate

Nelissen [157] has adopted a standard approach for the determination of FRs in polyester compounds (Figure 3.26). The analysis is complicated by spectral interferences of PET/PBT and by the complexity of FR structures, notably DBDPO, Saytex BT 93 W (ethylene-bis-tetrabromophthalimide), PDBS 80, Pyrochek 68PB, Saytex HP7010, Saytex 8010, FR1808, FR 1025, F 2400, BC 52 and BC 58 (brominated polycarbonate oligomers). 

Three flame retardants were compared in this study, namely, a brominated polycarbonate oligomer (58% bromine), a brominated polystyrene (68% bromine), and a brominated triaryl phosphate ester (60% bromine plus 4% phosphorus). These are described in Table I. Figures 1 and 2 compare the thermal stability of the brominated phosphate with commercial bromine-containing flame retardants by thermogravimetric analysis (TGA) and by differential scanning calorimetry (DSC). The brominated phosphate melts at 110°C and shows a 1% weight loss at 300°C. Brominated polycarbonate and brominated polystyrene are polymeric and are not as volatile at elevated temperatures as the monomeric flame retardants. 

The brominated phosphate is an efficient flame retardant for polycarbonate resin. UL-94 ratings of V-0 with oxygen index values of greater than 40 are obtained. Polycarbonate resin containing brominated phosphate processes with greater ease than resin containing brominated polycarbonate as measured by injection molding spiral flow measurements. The heat distortion temperature is reduced... 

The three flame retardants are compared in Table VI. Brominated phosphate disperses readily in the resin presumably due to its high solubility in aromatics. Resin containing brominated polycarbonate is relatively difficult to process as measured by injection molding spiral flow measurements. 

A 50/50 blend of polycarbonate resin and PBT polyester containing 13.5% brominated phosphate and no antimony oxide results in a product with a V-0 rating and an oxygen index of 33. An equivalent product containing brominated polycarbonate has a low oxygen index and burns in the UL-94 test (Table VIII). 

Various blend ratios of polycarbonate and PBT polyester were flame retarded with the three flame retardants. These data are shown graphically in Figure 3. Brominated phosphate is the most efficient and brominated polycarbonate the least efficient flame retardant. At a 50/50 ratio of polycarbonate/PBT, brominated phosphate is significantly more effective than brominated polystyrene. 

Brominated phosphate is a very efficient flame retardant as measured by oxygen index and UL-94 (Table IX and Figure 4). The melt index of the resin does not change with the addition of brominated polycarbonate, doubles with brominated polystyrene, and doubles again with brominated phosphate (Table IX). 

Figure 4. Flame Retarding Polycarbonate/PET Polyester Alloy 1. brominated polycarbonate oligomer 2. brominated polystyrene 3. brominated aromatic phosphate ester...

Generally, flame retardants for engineering PET compositions are based on bromine-containing compounds (such as brominated polycarbonate, decabro-modiphenyl oxide, brominated acrylic, brominated polystyrene, etc.). Such compounds are available commercially (such as from the Ethyl Chemical Corporation, Great Lakes Chemical Corporation, Dead Sea Bromine Company, etc.) In addition, the flame-retardant package generally contains a synergist, typically sodium antimonate. PET may also be flame-retarded with diarylphosphonate, melamine cyanurate or red phosphorus. 

Fire resistant polymers were obtained from brominated epoxynovolak resin, BPA/DC prepolymer, BMI, Zn acetate and benzoyl peroxide [103] or from an oligo-aspartimide (BMI-diamine reaction product), BPA/DC, 2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane (i.e. Tetrabromo-Bisphenol A) and 2-ethyl-4-methylimi-dazole [104]. A mixture of BPA/DC, BMI and epoxide resin with brominated polycarbonate, copoly[oxy-2,6-dimethylphenylene)-(oxy-2,3,6-trimethylphenylene)] and a catalyst was also suggested [105],... 

H. Sato, K. Kondo, S. Tsuge, H. Ohtani, and N. Sato, Mechanisms of thermal degradation of a polyester flame retarded with antimony oxide/brominated polycarbonate studied by temperature programmed analytical pyrolysis. Poly. Degr. Stab., 62, 41-48 (1998). 

SIM curves for representative degradation products and TIC curved observed for (a) PBT, (b) brominated polycarbonate (Br-PC), and (c) FR-PBT measured by TPPy-MS, from Ref. 33. The italic numbers in parentheses represent the peak heights. 

Sato, H., Kondo, K., Tsuge, S., Ohtani, H., and Sato, N., Thermal Degradation of Flame-Retarded Polyester with Antimony Oxide/Brominated Polycarbonate Studied by Temperature Programmed Analytical Pyrolysis Techniques, Polym. 

As additive flame-retardants, oligomeric brominated polycarbonate or deca-bromodiphenyl oxide may be combined with antimony trioxide. 

MECHANISMS OF THERMAL DEGRADATION OF A POLYESTER FLAME-RETARDED WITH ANTIMONY OXIDE/BROMINATED POLYCARBONATE STUDIED BY TEMPERATURE-PROGRAMMED ANALYTICAL PYROLYSIS... 

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