含硅-氮木质素协同聚磷酸铵阻燃聚乳酸

Synergistic flame retardant effect of lignin containing silicon-nitrogen with ammonium polyphosphate on polylactic acid

聚乳酸(PLA)作为生物基可降解塑料逐渐成为研究热点,但由于其极易燃烧,在包装、电器等领域的应用受到限制,为了解决此类问题,对碱木质素(Lig)改性合成了含硅-氮元素的木质素(Si-NLig),通过TGA分析发现,Si-NLig在空气中的初始降解温度(T5%)提高了20℃,且高温残留量由2.3%提高至25.5%。将Si-NLig作为成炭剂,与聚磷酸铵(APP)复配,通过熔融共混法制成阻燃聚乳酸材料(Si-NLig-APP/PLA),对其阻燃性能、力学性能、燃烧行为等进行了研究。研究表明:Si-NLig与APP质量比为1∶4,10wt%的添加量可使Si-NLig-8%APP/PLA的极限氧指数(LOI)值达到27%,UL-94垂直燃烧达到V-0级别,而同等条件下Lig-8%APP/PLA的LOI值为26%,UL-94仅为V-2级别。同时,与Lig-8%APP/PLA相比,Si-NLig-8%APP/PLA的热释放速率峰值(PHRR)降低了27%;残炭的拉曼图谱分析发现Si-NLig-8%APP/PLA的石墨化程度比Lig-8%APP/PLA提高了36.7%,为其良好的阻燃性能提供了理论依据。Si-NLig的引入使阻燃PLA力学性能得到了改善,拉伸强度提升了21%。可见Si-NLig在无卤阻燃PLA领域中具有潜在的应用前景。

Polylactic acid(PLA)as a biobased degradable plastic has increasingly become a research hotspot.However,PLA's application in packaging and electrical appliances is limited due to its high combustibility.In order to solve the above problem,lignin containing silicon-nitrogen synergistic(Si-NLig)was synthesized by modification of alkali lignin(Lig),and its TGA results showed that the temperature corresponding to mass loss 5wt% of material(T5%)increased by 20℃ and the high temperature residue increased from 2.3% to 25.5% in air.And Si-NLig was used as a charring agent,and compounded with ammonium polyphosphate(APP)to prepared flame retardant polylactic acid(Si-NLig-APP/PLA)by melt blending and hot-press molding,and the PLAs'flame retardant properties,mechanical properties,and combustion behavior,were investigated.The results showed that addition of 10wt%Si-NLig-APP with the mass ratio 1∶4 made Si-NLig-8%APP/PLA reach the limiting oxygen index(LOI)value of 27% and the vertical burning UL-94 V-0 level,while the LOI value of Lig-8%APP/PLA with Lig as charring agent at the same condition was 26% and the vertical burning UL-94 only passed V-2 rating.Meanwhile,the peak heat release rate(PHRR)reduced by 27% compared to Lig-8%APP/PLA.Raman spectroscopy was used to characterize the structure of the residual char after cone calorimeter testing,it was found that the degree of graphitization of Si-NLig-8%APP/PLA increased by 36.7% compared to that of Lig-8%APP/PLA,which provides a theoretical basis for its good flame retardancy.Introduction of Si-NLig led to the enhancement of mechanical properties of the flame retardant PLA with tensile strength increasing by 21%.It can be seen that Si-NLig has potential application prospect in the field of halogen-free flame retardant PLA.