光谱学与光谱分析, 2020, 40 (5): 1626, 网络出版: 2020-12-10  

基于TG-FTIR与XPS的硬质聚氨酯泡沫/膨胀石墨复合材料阻燃机理研究

Research of Flame Retardant Mechanism for RPUF/EG Composites Based on TG-FTIR and XPS
作者单位
安徽工业大学建筑工程学院, 安徽 马鞍山 243032
摘要
采用热重-傅里叶红外光谱(TG-FTIR)研究硬质聚氨酯泡沫(RPUF)和硬质聚氨酯泡沫/膨胀石墨复合材料(RPUF/EG)燃烧过程中气相产物生成及变化规律, 采用扫描电子显微镜(SEM)和X射线光电子能谱仪(XPS)研究其炭渣的微观形貌、 元素组成及键合状态, 结合阻燃性能测试阐明RPUF/EG复合材料阻燃机理。 SEM分析表明RPUF/EG复合材料燃烧后炭渣中存在大量 “蠕虫状”结构。 TG-FTIR分析表明RPUF/EG复合材料热解分为两个阶段, 第一个阶段对应于聚氨酯分子链硬段的降解, 第二个阶段对应于聚氨酯分子链软段的降解, 降解产物有异氰酸酯化合物、 胺类化合物、 碳氢化合物、 芳香族化合物、 CO、 CO2以及酯类化合物, RPUF/EG硬段降解产物强度高于PRUF的降解。 XPS分析表明RPUF炭渣中C, N和O元素含量分别为77.63%, 10.30%和12.07%, RPUF/EG30炭渣三种元素含量分别为82.18%, 9.18%和8.35%。 在此基础上, 通过对C元素的分峰拟合发现RPUF炭渣中C—C/C—H, C—O/C—N和CO/CN含量分别为51.38%, 38.89%和9.73%, RPUF/EG30炭渣中三种结构含量分别为53.99%, 37.62%和8.39%, 说明膨胀石墨的加入有利于聚氨酯分子链中C元素形成稳定石墨碳结构, 从而有利于形成致密炭层; 通过对N元素的分峰拟合发现RPUF炭渣中—NH—和N结构含量分别为49.06%和50.94%, RPUF/EG30炭渣中—NH—和N结构含量分别为43.96%和56.04%, 说明膨胀石墨的加入有利于聚氨酯分子链中N元素形成稳定芳杂环结构, 从而形成致密炭层; 通过对O元素的分峰拟合发现RPUF炭渣中O, —O—和O2/H2O三种结构含量分别为19.30%, 16.72%和63.98%, RPUF/EG炭渣中三种结构含量分别为25.57%, 36.60%和37.83%, 进一步说明RPUF/EG炭渣致密性明显提高。 综合TG-FTIR, XPS和SEM分析, 结合阻燃性能测试可以得出RPUF/EG复合材料阻燃机制: 膨胀石墨粒子在燃烧过程中膨胀形成“蠕虫状”结构, 其释放的酸性气体促进了聚氨酯分子链硬段的降解, 并且促进聚氨酯分子链中C和N等元素形成致密炭层, 上述致密炭层与“蠕虫状”结构一起覆盖在燃烧区域表面, 有效抑制燃烧区域物质以及能量的输运, 从而达到阻燃目的。 以上研究为揭示膨胀石墨阻燃机理, 拓展其在相关领域的使用提供了实验基础和理论依据。
Abstract
This work aims to research rigid polyurethane foam (RPUF) and rigid polyurethane foam/expanded graphite composites (RPUF/EG). Thermogravimetric analysis-Fourier transform infrared spectrophotometer (TG-FTIR) was applied to investigate generation and change law of gaseous phase products in combustion process. Scanning electron microscope (SEM) and X-ray photoelectron spectrometer (XPS) were used to investigate micro-morphology, elemental composition and bonding state of the char residue, which combined to flame retardant tests to discover flame retardant mechanism of PRUF/EG composites. SEM analysis revealed the existence of a lot of wormlike structure in char residue of RPUF/EG composites. TG-FTIR revealed that RPUF/EG composites presented two stages in decomposition process; the first one corresponded to decomposition of hard segment of polyurethane molecular chain, while the seconded one corresponded to decomposition of soft segment of polyurethane molecular chain. The pyrolysis products of RPUF and RPUF/EG composites included isocyanate compound, amine compound, hydrocarbons, aromatic compounds, CO, CO2 and esters, and RPUF/EG presented higher intensity of decomposition products for hard segment compared with RPUF. XPS revealed that char residue of RPUF contained C of 77.63%, N of 10.30%, O of 12.07%, while char residue of RPUF/EG30 contained C of 82.18%, N of 9.18%, O of 8.35%. Furthermore, peak fitting for bonding state of C element showed that C—C/C—H, C—O/C—N and CO/CN structure in char residue of RPUF were 51.38%, 38.89% and 9.73%, while those in char residue of RPUF/EG30 were 53.99%, 37.62% and 8.39%, indicating EG promote C element in polyurethane molecular chain to form stable graphite carbon structure, which was beneficial to form compact char layer. Peak fitting for bonding state of N element showed that —NH— and N structure in char residue of RPUF were 49.06% and 50.94%, while those in char residue of RPUF/EG30 were 43.96% and 56.04%, indicating EG promote N element in polyurethane molecular chain to form stable aromatic heterocyclic structure, which was also beneficial to form compact char layer. Peak fitting for binding state of O element showed that O, —O— and O2/H2O structure in char residue of RPUF were 19.30%, 16.72% and 63.98%, while those in char residue of PRUF/EG30 were 25.57%, 36.60% and 37.83%, indicating that the significant enhancement of compactness for the char residue of RPUF/EG composites. Based on TG-FTIR, XPS, SEM and flame retardant tests, flame retardant mechanism can be obtained as follows: EG particles expanded to form wormlike structure and released acid gas, which promoted the degradation of hard segment of polyurethane molecular chain. At the same time, EG promoted C and N element in polyurethane molecular chain to form compact char layer, which combined with wormlike structure to cover on the surface of combustion area, significantly inhibited mass and heat transmission, thus achieving the purpose of flame retardancy. The above researches provided experimental and theoretical basis for discovering flame retardant mechanism of EG and expanding further application in relative fields.

刘秀玉, 张冰, 张浩, 杜晓燕, 唐刚. 基于TG-FTIR与XPS的硬质聚氨酯泡沫/膨胀石墨复合材料阻燃机理研究[J]. 光谱学与光谱分析, 2020, 40(5): 1626. LIU Xiu-yu, ZHANG Bing, ZHANG Hao, DU Xiao-yan, TANG Gang. Research of Flame Retardant Mechanism for RPUF/EG Composites Based on TG-FTIR and XPS[J]. Spectroscopy and Spectral Analysis, 2020, 40(5): 1626.

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