Song Yan, Zong Xu, Wang Nan, Yan Ning, Shan Xueying, Li Jinchun
Faculty of Materials Science & Engineering, Changzhou University, Changzhou 213164, Jiangsu, China.
Jiangsu Key Laboratory of Environmentally Friendly Polymer Materials, Changzhou University, Changzhou 213164, Jiangsu, China.
Materials (Basel). 2018 Aug 22;11(9):1505. doi: 10.3390/ma11091505.
Lignin can be a candidate as a charring agent applied in halogen-free flame retardant polymers, and incorporation of silicon and nitrogen elements in lignin can benefit to enhancing its thermal stability and charring ability. In the present work, wheat straw alkali lignin (Lig) was modified to incorporate silicon and nitrogen elements by γ-divinyl-3-aminopropyltriethoxysilane, and the modified lignin (CLig) was combined with ammonium polyphosphate (APP) as intumescent flame retardant to be applied in poly(Lactic acid) (PLA). The flame retardancy, combustion behavior and thermal stability of PLA composites were studied by the limited oxygen index (LOI), vertical burning testing (UL-94), cone calorimetry testing (CCT) and thermogravimetric analysis (TGA), respectively. The results showed a significant synergistic effect between CLig and APP in flame retarded PLA (PLA/APP/CLig) occured, and the PLA/APP/CLig had better flame retardancy. CCT data analysis revealed that CLig and APP largely reduced the peak heat release rate (PHRR) and total heat release rate (THR) of PLA, indicating their effectiveness in decreasing the combustion of PLA. TGA results exhibited that APP and CLig improved the thermal stability of PLA at high temperature. The analysis of morphology and structure of residual char indicated that a continuous, compact and intumescent char layer on the material surface formed during firing, and had higher graphitization degree. Mechanical properties data showed that PLA/APP/CLig had higher tensile strength as well as elongation at break.
木质素可作为一种添加到无卤阻燃聚合物中的成炭剂，在木质素中引入硅和氮元素有助于提高其热稳定性和成炭能力。在本研究中，采用γ-二乙烯基-3-氨丙基三乙氧基硅烷对麦草碱木质素（Lig）进行改性，引入硅和氮元素，然后将改性木质素（CLig）与聚磷酸铵（APP）复配作为膨胀型阻燃剂应用于聚乳酸（PLA）中。分别通过极限氧指数（LOI）、垂直燃烧试验（UL-94）、锥形量热试验（CCT）和热重分析（TGA）研究了PLA复合材料的阻燃性能、燃烧行为和热稳定性。结果表明，CLig与APP在阻燃PLA（PLA/APP/CLig）中产生了显著的协同效应，PLA/APP/CLig具有更好的阻燃性能。CCT数据分析表明，CLig和APP大大降低了PLA的热释放速率峰值（PHRR）和总热释放速率（THR），表明它们在减少PLA燃烧方面的有效性。TGA结果表明，APP和CLig提高了PLA在高温下的热稳定性。对残炭的形态和结构分析表明，材料在燃烧过程中表面形成了连续、致密的膨胀炭层，且具有较高的石墨化程度。力学性能数据表明，PLA/APP/CLig具有较高的拉伸强度和断裂伸长率。
