High flame retardancy with significant suppression of toxic smoke and melt-dripping are challenging issues associated with flame-retardant thermoplastic polyurethane (TPU). To address these issues, in this work, graphene (Gr) was used as an effective two-dimensional smoke-toxicity suppressant with loadings less than 1 wt%, in combination with two efficient intumescent flame retardant (IFR) systems reported in our previous works. The IFRs were consisted of ammonium polyphosphate, pentaerythritol (PER), and melamine polyphosphate (MPP) with MPP:PER ratios of 10:1 (IFR1) and 1:1 (IFR2). Cone calorimeter test (CCT) results showed outstanding flame retardancy and excellent toxic smoke suppression in TPU/IFR1/0.75%Gr sample with reduced peak heat release rate (PHRR) by 85.3%, peak smoke production rate (PSPR) by 92.1%, and peak carbon monoxide production (PCOP) by 91.3% compared with neat TPU. TPU/IFR2/0.5%Gr sample exhibited a similar trend, with the PHRR, PSPR, and PCOP reduced by 66.8%, 62.5%, and 64.0%, respectively, with good anti-dripping property. The barrier function of graphene had a significant influence on reducing total smoke released in TPU/IFR1/0.75%Gr and TPU/IFR2/0.5%Gr samples by 82.1% and 34.3%, respectively, compared with their related TPU/IFRs composites. TPU nanocomposites reached a UL-94 V-0 rating and LOI of more than 29%. TGA results indicated improved char-forming, and FESEM depicted the graphitized integrated char structures. Mechanical performance of TPU/IFR2/0.5%Gr exhibited an enhanced ductility compared with the neat TPU. The possible flame retardancy mechanism was proposed based on the data obtained from the CCT, TGA, and EDS elemental analysis.

Graphical abstract

中文翻译：

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添加石墨烯增强膨胀型阻燃热塑性聚氨酯复合材料的烟雾/毒性抑制

高阻燃性以及显着抑制有毒烟雾和熔体滴落是与阻燃热塑性聚氨酯 (TPU) 相关的挑战性问题。为了解决这些问题，在这项工作中，石墨烯（Gr）被用作有效的二维烟雾毒性抑制剂，其负载量小于1 wt%，并与我们之前的工作中报道的两种高效膨胀阻燃剂（IFR）系统相结合。 IFR 由聚磷酸铵、季戊四醇 (PER) 和三聚氰胺聚磷酸盐 (MPP) 组成，MPP:PER 比例为 10:1 (IFR1) 和 1:1 (IFR2)。锥形量热仪测试（CCT）结果显示，TPU/IFR1​​/0.75%Gr 样品具有出色的阻燃性和优异的有毒烟雾抑制能力，峰值热释放率（PHRR）降低了 85.3%，峰值产烟率（PSPR）降低了 92.1%，与纯 TPU 相比，一氧化碳峰值 (PCOP) 减少 91.3%。 TPU/IFR2/0.5%Gr样品也表现出类似的趋势，PHRR、PSPR和PCOP分别降低了66.8%、62.5%和64.0%，具有良好的抗滴落性能。与相关的 TPU/IFR 复合材料相比，石墨烯的阻隔功能对 TPU/IFR1​​/0.75%Gr 和 TPU/IFR2/0.5%Gr 样品的总烟雾释放量有显着影响，分别减少了 82.1% 和 34.3%。 TPU纳米复合材料达到了UL-94 V-0等级，LOI超过29%。 TGA 结果表明炭形成得到改善，FESEM 描绘了石墨化的集成炭结构。与纯 TPU 相比，TPU/IFR2/0.5%Gr 的机械性能表现出增强的延展性。根据 CCT、TGA 和 EDS 元素分析获得的数据提出了可能的阻燃机理。

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