Preparation and properties of flame retardant rigid polyurethane foam composites based on microencapsulated ammonium polyphosphate and microencapsulated expanded graphite
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摘要: 采用原位聚合法,以聚氨酯为壳材,制备微胶囊化聚磷酸铵(PUAPP)和微胶囊化膨胀石墨(PUEG)。采用XPS、FTIR、TG和SEM分别对PUAPP和PUEG进行表征,结果表明,聚氨酯有效包覆在聚磷酸铵和膨胀石墨表面,成功制备了PUAPP和PUEG。在此基础上,采用一步法全水发泡工艺将PUAPP和PUEG引入到聚氨酯硬泡(RPUF)中,制备出一系列阻燃RPUF复合材料。采用极限氧指数(LOI)、垂直燃烧(UL-94)、TG、万能试验机、导热及密度测试研究了PUAPP/RPUF、PUEG/RPUF及PUAPP-PUEG/RPUF复合材料的阻燃性能、力学性能、保温性能及热稳定性。研究表明,微胶囊化阻燃剂的加入可以提高RPUF复合材料的高温稳定性,PUEG/RPUF、PUAPP/RPUF和PUAPP-PUEG/RPUF复合材料在700℃的残炭率从1.2wt%分别提高至6.9wt%、11.2wt%和10.7wt%。阻燃测试表明,PUAPP和PUEG可以有效提高RPUF复合材料的阻燃性能,当加入10.4wt% PUAPP时,PUAPP/RPUF复合材料的LOI提高到22.3vol%,UL-94等级为V-0级;当加入10.4wt% PUEG时,PUEG/RPUF复合材料的LOI达到25.3vol%,UL-94等级为V-0级;PUAPP-PUEG/RPUF复合材料的LOI达到24.3vol%,UL-94等级为V-0级。SEM和拉曼测试表明,PUAPP和PUEG可以提高RPUF复合材料的炭渣石墨化程度,使炭渣的致密性更强。Abstract: Microencapsulated ammonium polyphosphate (PUAPP) and microencapsulated expanded graphite (PUEG) were prepared by in situ polymerization with polyurethane as shell material. XPS, FTIR, TG and SEM were used to characterize PUAPP and PUEG. The results show that polyurethane is effectively coated on the surface of ammonium polyphosphate and expanded graphite, and PUAPP and PUEG are successfully fabricated. On this basis, a series of flame-retardant rigid polyurethane foam (RPUF) composites were prepared with PUAPP and PUEG loading by one-step water-blown method. The flame retardancy, mechanical properties, thermal insulation and thermal stability of PUAPP/RPUF, PUAPP/RPUF and PUAPP-PUEG/RPUF composites were investigated by limiting oxygen index (LOI), underwriters laboratories vertical burning test (UL-94), TG, universal testing machine, heat conduction and density test. The results show that the thermal stability at high temperature of RPUF composites can be improved by the addition of PUAPP and PUEG. The charresidues of PUAPP/RPUF, PUAPP/RPUF and PUAPP-PUEG/RPUF at 700℃ are increased from 1.2wt% to 6.9wt%, 11.2wt% and 10.7wt%, respectively. Flame retardant tests show that the microencapsulated flame retardant can effectively improve flame retardancy of RPUF composites. When 10.4wt% PUAPP is added, the LOI of the PUAPP/RPUF composite is increased to 22.3vol% with V-0 rating in UL-94 test; when 10.4 wt% PUEG is added, the LOI of the PUAPP/RPUF composite is increased to 25.3vol% with UL-94 V-0 rating; PUAPP-PUEG/RPUF composite presents LOI of 24.3vol% with UL-94 V-0 rating. SEM and Raman tests indicate that PUAPP and PUEG can increase graphitization degree of char residues for RPUF composites with enhanced compactness of the char residues.
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表 1 硬质聚氨酯泡沫(RPUF)、微胶囊化聚磷酸铵(PUAPP)/RPUF、微胶囊化膨胀石墨(PUEG)/RPUF和PUAPP-PUEG/RPUF复合材料配比
Table 1. Formulation of rigid polyurethane foam (RPUF), microencapsulated ammonium polyphosphate (PUAPP)/RPUF, microencapsulated expanded graphite (PUEG)/RPUF and PUAPP-PUEG/RPUF composites
Sample LY-4110/g PM-200/g LC/g AK-8805/g A33/g TEOA/g Water/g PUEG/g PUEG/wt% PUAPP/g PUAPP/wt% RPUF 100 150 0.5 2 1 3 2 0 0 0 0 PUEG/RPUF 100 150 0.5 2 1 3 2 30 10.4 0 0 PUAPP/RPUF 100 150 0.5 2 1 3 2 0 0 30 10.4 PUAPP-PUEG/
RPUF100 150 0.5 2 1 3 2 10 3.5 20 6.9 Notes: LY-4110—Polyether polyol; PM-200—Polyarylpolymethyleneisocyanate; LC—Dibutyltindilaurate; AK-8805—Silicone surfactant; A33—Triethylenediamine; TEOA—Triethanolamine. 表 2 空气条件下APP、PUAPP、EG和PUEG的TGA数据
Table 2. TGA data of APP, PUAPP, EG and PUEG under air conditions
Sample T−5%/℃ Tmax1/℃ Tmax2/℃ Residues at 700℃/wt% APP 331 357 606 10.4 EG 204 215 — 24.8 RPUF 271 313 569 1.2 PUAPP 285 299 568 10.0 PUEG 203 216 — 21.8 Notes: T−5%—Onset degradation temperature; Tmax1, Tmax2—Maximum decomposition temperature in the first and second stage, respectively. 表 3 空气条件下RPUF、PUAPP/RPUF、PUEG/RPUF和PUAPP-PUEG/RPUF的TGA数据
Table 3. TGA data of RPUF, PUAPP/RPUF, PUEG/RPUF and PUAPP-PUEG/RPUF under air conditions
Sample T−5%/℃ Tmax1/℃ Tmax2/℃ Residues at 700℃/wt% RPUF 271 312 569 1.2 PUEG/RPUF 249 319 572 6.9 PUAPP/RPUF 264 315 565 11.2 PUAPP-PUEG/RPUF 262 308 566 10.7 表 4 RPUF、PUAPP/RPUF、PUEG/RPUF和PUAPP-PUEG/RPUF复合材料的密度、导热系数和压缩强度
Table 4. Density, thermal conductivity and compressive strength of RPUF, PUAPP/RPUF, PUEG/RPUF, PUAPP-PUEG/RPUF composites
Sample RPUF PUEG/RPUF PUAPP/RPUF PUAPP-PUEG/RPUF ρ/(kg·m−3) 64.16±0.91 57.92±0.23 59.92±5.77 55.84±1.36 λ/(W(m·K)−1) 0.0390±0.00038 0.0394±0.000436 0.0389±0.000493 0.0395±0.00029 Pressure/MPa 0.325±0.0075 0.276±0.0151 0.286±0.0205 0.271±0.0411 Notes: ρ—Density; λ—Thermal conductivity; Pressure—Compressive strength. -
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