水相自组装生物基核壳膨胀型阻燃剂对聚乳酸的阻燃改性

Flame Retardant Modification of Polylactic Acid by Bio-Based Core-Shell Intumescent Flame Retardant Self-Assembled in Aqueous Phase

针对聚乳酸(PLA)的生物基阻燃体系存在相容性差或合成工艺复杂、有机溶剂用量大等问题,文中采用水相自组装法,制备了以聚磷酸铵(APP)作为"核",以壳聚糖(CS)、植酸钠盐(PA-Na)作为"壳"的生物基核壳膨胀型阻燃剂APP@CS@PA-Na,研究其不同用量对PLA的阻燃性能、热降解及力学性能的影响。结果表明,当APP@CS@PA-Na的添加量为10%时,PLA可以通过UL94 V0级,氧指数达到30.5%,热释放峰值及总热释放速率分别降低了33.0%和19.4%。残炭分析发现,APP@CS@PA-Na不仅能促进PLA成炭,还有助于提高残炭中的磷含量及石墨化程度,其添加量是影响保护性炭层"质"与"量"的重要因素。在氮气氛围下的热失重测试也表明其促进成炭行为。APP@CS@PA-Na的添加量在合理范围内时,其对PLA具有一定的增韧作用。添加10%APP@CS@PA-Na的PLA的断裂伸长率和冲击强度比纯PLA分别提高了28%和17%。

Due to the problems such as the poor compatibility of bio-based flame retardant system and their complex synthesis processes with large amounts of organic solvents,the core-shell intumescent flame retardant APP@CS@PA-Na,with ammonium polyphosphate(APP)as"core",chitosan(CS)and sodium phytate(PA-Na)as"shell",was prepared by aqueous self-assembly method.The effects of different additions of APP@CS@PA-Na on flame retardancy,thermal degradation and mechanical properties of polylactic acid(PLA)were studied.The results show that when the mass fraction of APP@CS@PA-Na is 10%,PLA can pass the UL94 V0 and its limited oxygen index reaches 30.5%;the peak heat release rate and total heat release rate are decreased by 33.0%and 19.4%respectively.Through the residual char analysis,it is found that APP@CS@PA-Na can not only promote the charring of PLA,but also improve the phosphorus content and graphitization degree of the char.The amount of APP@CS@PA-Na is an important factor affecting the"quality"and"quantity"of the protective carbon layer.The thermal gravimetric analysis in N2 also show that it can promote the charring behavior.The appropriate amount of APP@CS@PA-Na could endow PLA with a certain toughening effect.The elongation at break and impact strength of PLA with 10%APP@CS@PA-Na are increased by 28%and 17%respectively compared with pure PLA.