In this work, new lignin-based flame retardant LHDs were successfully synthesized through the reaction between lignin, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and hexamethylene diisocyanate (HDI). The chemical structure of LHD was characterized by FTIR, ~(1) H NMR, ~(31) P NMR. The thermal stability of LHD was studied by TGA. The results showed that the residual carbon content of L15HD (15% of lignin in LHD) at 600 °C reached 16.55%, indicating that this prepared flame retardant can be a type of good char forming agent. LHDs were then applied to prepare flame-retardant lignin-based polyurethane (FLPU). Lignin-based polyurethane (LPU) was synthesized by the reaction between lignin, polyethylene glycol 200 (PEG 200) and hexamethylene diisocyanate (HDI). The limiting oxygen index (LOI) value of the FLPU reached 30.2% when the addition content of L15HD (15% lignin in LHD) in L _(20) PU (20% lignin in LPU) was 25%, exhibiting excellent flame-retardant properties. Scanning electron microscopy (SEM) analysis of the FLPU char residual showed that there was a continuous dense outer carbon layer on the residue surface, and the inner carbon layer had many expansion bubbles, indicating the LHDs have an excellent flame retardant effect for PU. In addition, FLPU presented better hardness and adhesion than PU. The hardness of F _(L15-25) L _(20) PU (lignin content in LPU was 20%, and added content of L15HD in LPU was 25%) reached 4H, and its adhesion was 0. These excellent properties illustrated that the LHDs are ideal flame retardants and reinforcing agents for LPU because of the co-curing and strong interface between LHD and LPU.
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机译：在这项工作中，通过木质素，9,10-二氢-9-氧杂-10-磷菲基-10-氧化物（DOPO）和六亚甲基二异氰酸酯（HDI）的反应成功合成了新的木质素基阻燃剂LHD。 LHD的化学结构通过FTIR，〜（1）H NMR，〜（31）P NMR表征。通过TGA研究了LHD的热稳定性。结果表明，L15HD的残余碳含量（LHD中木质素的15％）在600°C时达到16.55％，表明该阻燃剂可作为良好的成炭剂。然后将LHD应用于制备阻燃木质素基聚氨酯（FLPU）。通过木质素，聚乙二醇200（PEG 200）和六亚甲基二异氰酸酯（HDI）之间的反应合成了木质素基聚氨酯（LPU）。当L _（20）PU（LPU中20％木质素）的L15HD（LHD中木质素的15％）的添加量为25％时，FLPU的极限氧指数（LOI）值达到30.2％，表现出优异的阻燃性属性。扫描电子显微镜（SEM）对FLPU炭残留物的分析表明，残留物表面上有连续的致密外部碳层，内部碳层有许多膨胀气泡，表明LHDs对PU具有优异的阻燃作用。此外，FLPU的硬度和附着力比PU高。 F _（L15-25）L _（20）PU的硬度（LPU中的木质素含量为20％，LPU中的L15HD的添加含量为25％）达到4H，附着力为0。这些优异的性能说明由于LHD和LPU之间的共固化和牢固的界面，LHD是LPU的理想阻燃剂和增强剂。
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