Thermal stability and flame retardancy of PMMA composites filled with metal oxalates

Abstract

In this thesis, PMMA composites filled with metal oxalates as flame retardants were invented by solution blending method. Metal oxalates as flame retardants are environmentally friendly flame retardants and safe, halogen-free flame retardant and no toxic fume generation. From the TGA results obtained, thermal stability of the composites filled with metal oxalates was observed increasing with the amount of metal oxalates. From the Micro calorimeter results obtained, HRR (Heat Release Rate) reduction of the composites filled with metal oxalates was observed increasing with the amount of metal oxalates. Through LOI results, PMMA composites filled with 16.7 wt% of metal oxalates were in nonflammable region. And we confirmed well-dispersed metal oxalate particles by SEM. Moreover, the synergistic effect of CNT and zinc oxalate on flame retarding the PMMA composites was also investigated in this thesis. By means of micro calorimeter tests, it was found that the addition of CNT can produce synergistic effect on flame-retarding PMMA/zinc oxalate system. Because CNT(carbon nanotubes) contains network structured layer, it was formed without any major cracks or openings during the burning tests. The network layer acts as a heat shield to slow the thermal degradation of PMMA. During thermal decomposition of zinc oxalate, it released carbon dioxide. The carbon dioxide has diluting effect in the gas phase and surrounds the compound surface to lower the concentration of oxygen and burnable gases. Through the analysis of photo, it was proved that the barrier effect of the char layer was promoted when CNT was added and thus the decomposition of zinc oxalate and polymer matrix under the char layer was retarded.