writer：Jiang Gong, Nana Tian, Xin Wen, Xuecheng Chen, Jie Liu, Zhiwei Jiang, Ewa Mijowska, Tao Tang*
keywords：Poly(lactic acid), Fumed silica, Ni2O3, Flame retardancy, Catalytic carbonization
source：期刊
specific source：Polymer Degradation and Stability 104 (2014) 18-27
Issue time：2014年
A novel combined catalyst of fumed silica (SiO2) with Ni2O3 was demonstrated to be more efficient than SiO2 or Ni2O3 alone in enhancing the char yield of poly(lactic acid) (PLA) and improving its char layer structure, which greatly enhanced the flame retardancy of PLA. The results of field-emission scanning electron microscope, transmission electron microscope, X-ray diffraction, Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy revealed that the residual chars mainly consisted of block-like carbon and carbon nanotubes with some surface functional groups. The flame retardancy of PLA and its composites was studied by cone calorimeter test. The heat release rate and total heat release of PLA composites containing both SiO2 and Ni2O3 decreased significantly in comparison with those of neat PLA. The investigation of the synergetic mechanism showed that in the presence of both SiO2 and Ni2O3, a large amount of chars were in situ formed from the catalytic carbonization of degradation products of PLA by Ni2O3 during combustion. This not only reduced the release of flammable degradation products, but also acted as an insulating barrier to prohibit the oxygen and feedback of heat from reaching the underlying substrate. On the other hand, the formation of a percolated network structure of SiO2 and Ni2O3 particles in PLA matrix increased the melt viscosity of PLA and facilitated the formation of a more compacted protective layer, which promoted the flame retardancy of PLA.