Investigation On The Preparation, Properties And Thermal Decomposition Mechanism Of The Flame-retardant ABS

Recently, there had a rapid development in the fields of automobile, home appliances andelectronic apparatus with the macro adjustment of national monetary policy and the gradualimprovement of the living standards. It promotes the rapid expansion of the flame-retardantplastics that are used widely in these fileds. Above63%of the flame-retardant plastics wererequired to pass the UL94V-0test.As a kind of thermoplastics with comprehensive performances, ABS has been usedwidely in many fields such as electronic equipment, automobiles, domestic appliances,architectures and so on. However, it is difficult for no-charrable ABS to obtain halogen-freeflame retardant ABS with satisfied mechanical properties and flame retardant properties（UL94V-0）. On the other hand, the halogen flame retardant ABS in a V-0rating will be restrictedby rigorous requirement of environmental disciplines. It is thus necessary and urgent todevelop a new environment-friendly flame retardant ABS in a V-0rating which can beaccepted by the market and environment at the same time.To solve these above-mentioned problems, hydrophobic magnesium hydroxide （MH）nano-particles were firstly prepared. The flame-retardant ABS blends were prepared throughmelt blending using magnesium hydroxide/brominated polystyrene（BPS） andPOE-g-MAH/ABS high-rubber powders as hybrid flame retardants and synergetic tougheners,respectively. And the mechanical properties, fire-resistance, thermal stability and thermaldecomposition mechanism were investigated.The main research work and results were listed as follows:（1）Hydrophobic magnesium hydroxide nano-particles were prepared visa directprecipitation method by using brine and ammonia as raw materials, lanthanum stearate assurface modifier at room temperature. The product was characterizated via hydrophobic test,SEM, FT-IR, TG and XRD, respectively. ABS/MH blends were prepared through melt compounding, and the influence of the modification of MH on the the mechanical propertieswere investigated. The results showed that the hydrophilic MH particles were changed to behydrophobic after the chemical modification in the presence of lanthanum stearate andmagnesium hydroxide, and the modified MH particles improved the mechanical properties ofABS/MH blends as compared to the un-modified MH.（2） The flame retardant ABS multi-component blends were prepared through meltblending in the presence of hybrid flame-retardants （hydrophobic MH and BPS/Sb₂O₃） andcomposite tougheners （POE-g-MAH and ABS high rubber powders）. The mechanicalproperties, fire-resistance of the blends and the synergistic effect between MH and BPS/Sb₂O₃were studied. The results showed that the limiting oxygen index of ABS with40phr MH and20phr BPS/Sb₂O₃was up to25, and it passed the UL-94V-0test. The Izod impact strength ofABS blends was raised up to6.7kJ/m2at40wt%tougheners loading level, and and thefire-resistance of ABS blends almost no change with the incorporation of the toughners. Italso demonstrated that MH showed a synergistic effect with BPS/Sb₂O₃. With the addition ofMH, the content of BPS/Sb₂O₃for blends to pass the UL-94V-0test was reduced from25phrto20phr，the smoke formation was also reduced and the melt drip was inhibited at the sametime. On the other hand, the addition of BPS/Sb₂O₃was found to improve the flameretardancy of magnesium hydroxide.（3）The thermal properties of ABS, ABS/MH and ABS/MH/BPS/Sb₂O₃blends werestudied through TG. The degradation activation energies were calculated through Kissingermethod and Flynn-Wall-Ozawa method, from which the thermal degradation kinetics wasanalyzed. It was found that the thermal stability and the degradation activation energy of ABSwere higher than that of ABS/MH/BPS/Sb₂O₃but lower than that of ABS/MH. It could beattributed to the efficiency and mechanism of different flame retardants. Br-Sb system withhigher efficiency took effect in the gas phase, while MH with lower efficiency had its effect inthe condensed phase. When MH was used alone, it worked in the condensed phase, and thedegradation activation energy was increased. By contrast, Br-Sb system with higher efficiency played the main role in the gas phase when the composite flame retardant was used, which ledto the reduction of the degradation activation energy.