Study On Thermal Stability Of Brominated Flame Retardant Hexabromocyclododecane

Hexabromocyclododecane（Hereinafter referred to as HBCD） is highly efficientflame retardant for polystyrene, polypropylene polymer. It has many advantages such ashigh bromine content, good flame retardant effect, and little adding quantity and so on.But it also has some disadvantages such as poor thermal stability, low decompositiontemperature. HBCD without the stabilization starts to decompose and releases hydrogenbromide, which cause corrosion to processing equipment, make the products coloring, andaffect the operating environment, impair the health of workers. Therefore, it is verynecessary to increase the decomposition temperature of HBCD and to improve its thermalstability.In this paper, the thermostable HBCD has been prepared by dry powder blendingmethod, microencapsulation and metal carboxylate coprecipitation method. The processconditions were optimized, the product was characterized by thermogravimetric analyzer(TGA)，scanning electron microscope (SEM)，X-ray photoelectron spectroscopy (XPS)and infrared spectrum (IR). The results show that the decomposition temperature of theproduct was significantly increased, the thermal stability was improved by the above threemethods, and the product can meet the requirements of plastic processing.In this paper, the effects of dosage of heat stabilizer antimony trioxide and polymerresin M on the thermal stability of HBCD were studied. The thermal decompositiontemperature of HBCD can be effectively improved by dry blending HBCD with polymerresin-antimony trioxide. The effect of stabilization for HBCD is still very significant withadding small amounts of the thermal stabilizer. When the addition amount of the thermalstabilizer was5%, the decomposition temperature of HBCD could reach245℃. Theeffects of this method on mechanical properties and bromine content of HBCD were small,and this method could effectively reduce the production cost.HBCD was respectively microencapsulated with Sb2O3and Sb2O5sol. The effects ofthe coating conditions on the thermal decomposition temperature of HBCD microcapsulewere studied. The optimum process conditions with antimony trioxide as capsule materialof coated HBCD are as follows: the mass ratio of core and wall (HBCD/Sb2O3)10:2.5, thecomposite dispersant with the mass ratio of Span80and Tween801:1, reactiontemperature65℃, coating time140min. It is known by SEM and XPS that the microcapsule has complete coating, good thermal stability and decomposition temperature246℃. The optimum process conditions with Sb2O5sol as capsule material of coatedHBCD are as follows: ammonium dihydrogen phosphate as stabilizer, stabilizer dosage4%(NaSb (OH)6as a benchmark), the mass ratio of HBCD and NaSb(OH)610:3, reactiontemperature90℃, reaction time is3h, stirring speed300r/min. In these conditions，themicrocapsule has better thermal stability.HBCD was modified by metal carboxylate coprecipitation. The effects of the kindsand dosage of metal carboxylate on the decomposition temperature were studied. Theoptimum process conditions for HBCD coprecipitation with rare earth carboxylate ormetal carboxylate are as follows: four bromine phthalic acid as carboxylic acid, the massratio of HBCD and LaCl310:3.0; the mass ratio of HBCD and AlCl310:2.0, the mass ratioof HBCD and MgSO410:2.5, pH10, the experiment temperature95℃for first step,60℃for second step, Tween-80as emulsifier, emulsifier dosage about0.6g. When stearicacid instead of four bromine phthalic acid was choosed as carboxylic acid, the mass ratioof HBCD and lanthanum chloride was10:1.5. When HBCD coprecipitated withLanthanum stearate/Magnesium stearate, the thermal decomposition temperature ofHBCD was significantly increased, which could reach more than250℃. When massratio of lanthanum chloride and magnesium sulfate was1:1, the decompositiontemperature of HBCD could reach257℃.