笼型八苯基硅倍半氧烷与聚磷酸铵对聚乳酸的协同阻燃研究

The flame retardancy of poly(lactic acid) (PLA) was for the first time improved by a synergistic effect between octaphenyl silsesquioxane (OPS) the organic-inorganic hybrid and ammonium polyphosphate (APP) the inorganic phosphorus-based flame retardant. PLA/OPS, PLA/APP, and PLA/OPS+APP composites fabricated by twin-screw melt blending were subjected to a series of characterizations, including vertical test, cone calorimetry, and limiting oxygen index measurements. Remarkable enhancement was achieved for the flame retardant properties of PLA/OPS+APP, as OPS and APP could reduce synergistically the heat release rate (HRR) of PLA. Dispersion of OPS and APP in the PLA matrix was observed by scanning electron microscopy (SEM), while thermal stability of the composites prepared was studied via thermogravimetric analysis (TGA). For an in-depth understanding of the combustion process, morphology and elemental composition of the char residues after cone calorimetry test were further investigated through SEM, energy dispersive X-ray spectrometry, and X-ray photoelectron spectroscopy. Results showed that both OPS and APP were uniformly distributed in the PLA matrix. Besides, the initial decomposition processes of APP and PLA were in good accordance with each other, while the thermal decomposition process of OPS agreed well with that of APP at high temperature; such matching decomposition processes and synergism between OPS and APP gave rise to an improved thermal stability of the PLA composites prepared. Apart from the reduction of HRR peak, OPS/APP synergy could diminish significantly the retardant-induced smoke release while maintaining a satisfactory tensile performance for the PLA material. Finally, underlying mechanisms of the specific combustion process were tentatively proposed for the three kinds of flame-retardant PLA composites.