A COMPARATIVE-EVALUATION OF A NOVEL FLAME-RETARDANT, 3-(TETRABROMOPENTADECYL)-2,4,6-TRIBROMOPHENOL (TBPTP) WITH DECABROMODIPHENYLOXIDE (DBDPO) FOR APPLICATIONS IN LDPE-BASED AND EVA-BASED CABLE MATERIALS

Flame retardation of polymeric materials for cables is becoming a stat utory requirement due to governmental regulations to protect life and property from damages caused by fire. This and other factors such as t he ever-increasing cost of existing flame retardants (FRs) have given rise to the search for better FRs. In this article, the suitability of an FR, 3-(pentadecyltetrabromo)-2,4,6-tribromophenol (TBPTP) develope d from cardanol was evaluated for use in cable insulating and jacketin g materials based on low-density polyethylene (LDPE) and ethylene viny l acetate (EVA). The processability, mechanical properties, compatibil ity and miscibility, thermal behavior, flammability behavior, smoke ge neration, acid emission, aging characteristics etc., of the blends of the FR with LDPE and EVA were studied in comparison to those of decabr omodiphenyl oxide (DBDPO), which is a standard FR used by the cable in dustry. Although TBPTP is found to be less thermally stable than is DB DPO, it exhibited better flame retardancy and has comparable thermal s tability when blended with LDPE and EVA. Both LDPE-TBPTP and EVA-TBPTP blends produced less smoke than did the corresponding blends of DBDPO . In the case of the EVA-TBPTP blend, the percentage emission of smoke was almost negligible, placing EVA-TBPTP under the low smoke grade. F ormulations containing a synergistic agent, promoter, and filler with the corresponding FR and polymer polymer along with an antioxidant wer e extruded out into wire and tested for cable properties. At 20% loadi ng, the LOI values of the blends were 34.6 and 32.5, respectively, for the TBPTF-EVA and DBDPO-EVA blends. Vertical burning tests carried ou t with EVA-TBPTP cable showed that it is self-extinguishable. The proc essability of the compositions containing TBPTP were better than those of DBDPO. The improved processability was found to be due to the plas ticising effect of TBPTP. SEM pictures of the blend showed excellent d istribution of TBPTP in the polymer, indicating good compatibility and miscibility. Comparatively, DBDPO did not exhibit uniform distributio n. The mechanical properties of the blends were within specifications of standard cable materials except that the % elongation of the DBDPO- LDPE blend was far too low. Aging studies also gave better properties for the TBPTP system than for those of the DBDPO system. The overall r esults show that the properties of EVA-TBPTP cable fall within specifi cations for the FARLS grade, whereas the EVA-DBDPO cable did not. In t he case of LDPE, both TBPTP and DBDPO did not satisfy specifications f or the FRLS grade, but the data indicate that they can be used as FRs. The superiority in properties of the TBPTP system over DBDPO is expla ined in terms of the structure of TBPTP characterized by the distribut ion of the flame-retardant element, bromine, almost evenly between the aliphatic and aromatic moieties of the molecule, which can, in contra st to the fully aromatic DBDPO, provide halogen over a wide range of t emperatures to the combustion zone of the decomposing polymer. Moreove r, tile presence of the aliphatic segment assures improved processabil ity and compatibility. (C) 1997 John Wiley & Sons, Inc.