基于光谱学分析的硬质聚氨酯泡沫/钢渣/次磷酸铝复合材料阻燃机理研究

Research of Flame Retardant Mechanism of Rigid PolyurethaneFoam/Steel Slag/Aluminum Hypophosphite CompositesBased on Spectroscopy Analysis

硬质聚氨酯泡沫(RPUF)的优异性能使其在各领域被广泛应用,但本身的易燃性为其在应用过程中埋下了巨大的安全隐患。钢渣(SS)作为提炼铁精矿后排放的固体废弃物,因其综合利用效率低下而造成一系列环境污染问题。为提高RPUF火灾安全性和钢渣的附加值,将SS和次磷酸铝(AHP)引入到RPUF中,采用一步全水发泡法,制备一系列阻燃RPUF(FR-RPUF)复合材料。利用射线荧光光谱分析(XRF)探究了SS的化学成分,并系统研究了SS/AHP对FR-RPUF复合材料的微观形貌、热稳定性、阻燃性能以及气相产物的影响。XRF测试表明:钢渣的化学成分主要是CaO、SiO_(2)、Al_(2)O_(3)、Fe_(2)O_(3)、SO_(3)、MgO,以上金属氧化物能够作为协效剂促进聚合物成炭,并覆盖在材料表面阻隔燃烧热,在凝聚相达到阻燃目的。扫描电镜(SEM)测试表明:SS/AHP与RPUF基体的相容性较差导致FR-RPUF的泡孔出现不同程度的破损。阻燃测试表明:RPUF-1、RPUF-4、RPUF-5的极限氧指数分别为24.2 vol%、23.4 vol%、19.7 vol%,说明SS和AHP存在一定的协效阻燃作用,且RPUF/SS/AHP复合材料全部通过UL-94 V-0级别,满足外墙保温材料使用要求。热重-红外分析(TG-FTIR)测试表明:SS/AHP并未改变RPUF的降解过程,气相产物主要为碳氢化合物、羰基化合物、氨基甲酸酯、CO_(2)、异氰酸酯化合物、芳香族化合物、氰化氢、羰基化合物和酯类。对典型挥发性产物进一步分析发现,AHP和SS的加入促进RPUF基体早期降解。拉曼测试表明:当SS/AHP加入到RPUF后,RPUF-4的D峰与G峰的峰面积比(I_(D)/I_(G))值最小,表明SS/AHP的加入提高了FR-RPUF复合材料炭渣的致密性、石墨化程度。结合上述分析提出阻燃机理:首先AHP吸热分解,降低了火焰周围的温度,其分解的PO·自由基捕获游离的HO·抑制连锁反应,分解产生的焦磷酸铝与炭渣覆盖在基体表面,抑制了火焰和可燃气体的扩散。AHP分解产生的PH3遇氧气生成酸性物质(磷酸和聚磷酸),促进了RPUF脱水成炭,并且钢渣中的矿物成分会与磷酸或聚磷酸反应,形成致密炭层,与AHP共同发挥协效阻燃作用。研究为SS和AHP复配阻燃硬质聚氨酯泡沫材料提供理论依据和实验基础。

The excellent performance of rigid polyurethane foam(RPUF)makes it widely used in various fields,but its flammability has laid an enormous security risk in the application process.As a solid waste discharged after refining iron concentrate,steel slag(SS)causes environmental pollution problems due to its low comprehensive utilization efficiency.To improve the fire safety of RPUF and the added value of steel slag,SS and aluminium hypophosphate(AHP)were introduced into RPUF.A series of flame retardant RPUF(FR-RPUF)composites were prepared using one-step water-blown method.The chemical composition of SS was investigated by X-ray fluorescence spectroscopy(XRF),and the effects of SS/AHP on the microstructure,thermal stability,flame retardancy and gas phase products of FR-RPUF composites were systematically studied.XRF test showed that the chemical components of steel slag were mainly CaO,SiO_(2),Al_(2)O_(3),Fe_(2)O_(3),SO_(3),MgO,et al,which could be used as synergistic agents to promote the char formation of polymer and cover the surface of the material to block combustion heat,to achieve the purpose of condensed phase flame retardant.Scanning electron microscope(SEM)test indicated that the poor compatibility between SS/AHP and RPUF matrix led to varying degrees of damage of FR-RPUF cells.The flame retardant tests made known that the limiting oxygen indexes of RPUF-1,RPUF-4,and RPUF-5 were 24.2 vol%,23.4 vol%,and 19.7 vol%,respectively,indicating that SS and AHP had a synergistic flame retardant effect.The RPUF/SS/AHP composites all passed UL-94 V-0 level,meeting the requirements of external wall insulation materials.Thermogravimetry-infrared(TG-FTIR)analysis showed that SS/AHP did not change the degradation process of RPUF.The gaseous products were mainly hydrocarbons,carbonyl compounds,carbamates,CO_(2),isocyanate compounds,aromatic compounds,hydrogen cyanide,carbonyl compounds and esters.TG-FTIR tests implied that RPUF and FR-RPUF generated carbamates,hydrocarbons,CO_(2),isocyanates,carbonyl compounds,aromatic compounds,esters and hydrogen cyanide.Further analysis of typical volatile products showed that the addition of AHP and SS promoted the early degradation of RPUF matrix.Raman test confirmed that the peak area ratio(I_(D)/I_(G))of D peak to G peak of RPUF-4 was the smallest when SS/AHP was added to RPUF,indicating that the addition of SS/AHP improved the compactness and graphitization degree of FR-RPUF composites.The flame retardant mechanism was proposed.Firstly,AHP endothermic decomposition reduced the temperature around the flame,and the decomposed PO free radicals captured free HO·to inhibited the chain reaction.Secondly,the decomposed aluminum pyrophosphate and char layer were covered on the substrate surface,which inhibited the diffusion of flame and combustible gas.The PH3 produced by AHP decomposition reacted with oxygen to form acidic substances(phosphoric acid and polyphosphoric acid),which promoted the dehydration of RPUF into char.The mineral components in steel slag reacted with phosphoric acid or polyphosphoric acid to form a dense char layer,which played a synergistic flame retardant effect with AHP.