Preparation and flame retardancy of titanium carbide-manganese dioxide/thermoplastic polyurethane nanocomposites
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摘要: 热塑性聚氨酯(TPU)具有优良的性能,现已广泛应用于生产生活的各个领域。但该材料是一种有机高分子材料,具有高度易燃性,且燃烧时会发生熔融滴落现象,同时产生大量CO、CO2、NOx等有毒、窒息性气体,限制了TPU的应用。将层状碳化钛(Ti3C2Tx)与二氧化锰(MnO2)通过界面调控技术制备为MXene(一类二维无机化合物,碳化钛是其中的一种)基杂化阻燃剂(Ti3C2Tx-MnO2),然后再引入TPU材料形成MXene/TPU基杂化物纳米复合材料(Ti3C2Tx-MnO2/TPU),利用TGA、XRD、SEM等进行检测。结果显示,在Ti3C2Tx-MnO2/TPU纳米复合材料中,700℃时炭渣含量最大程度提高91.89%,总热释放量(THR)、总烟释放量(TSR)、CO释放总量(CO TY)和CO2释放总量(CO2 TY)相较于纯TPU分别最大程度降低了28.62%、33.41%、34.12%和29.77%。通过分析,MXene基杂化阻燃剂中Ti3C2Tx氧化为TiO2,并与MnO2协同催化成炭,大幅度提高纳米复合材料燃烧后炭层连续性和致密性,阻隔热量、阻挡氧气进入并抑制烟气释放。Abstract: Thermoplastic polyurethane elastomer (TPU) was equipped with excellent properties, which was widely used in various fields of industry and living. However, the application scope of TPU was limited because the material was a kind of organic polymer material with high inflammability. Moreover, a large amount of CO, CO2, NOx and other toxic asphyxiating gases from TPU material were released during combustion. The design of MXene-based hybrid flame retardant based on layered titanium carbide (Ti3C2Tx) and manganese dioxide (MnO2) was proposed for preparation of MXene-based hybrid/TPU nanocomposites. The mechanisms of flame retardancy, smoke suppression and toxicity reduction of the TPU nanocomposites were studied by means of TGA, XRD, SEM and other techniques. In the case of Ti3C2Tx-MnO2/TPU systems, the total heat release (THR), the total smoke release (TSR), the total CO yield (CO TY) and the total CO2 yield (CO2 TY) of the TPU nanocomposite were maximally decreased by 28.62%, 33.41%, 34.12% and 29.77% respectively compared to those of TPU, besides 91.89% increase in residual char at 700℃. According to the analysis, Ti3C2Tx in MXene-based hybrid flame retardant was oxidized to TiO2 and co-catalyzed with MnO2 to form carbon, which not only improved the continuity and compactness of carbon layer after combustion of nanocomposite materials, but also blocked the entry of heat and oxygen and inhibit the release of flue gas.
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图 6 锥形量热仪测试后样品炭渣的数码照片:(a) TPU;(b) MnO2/TPU;(c) Ti3C2Tx/TPU;(d) Ti3C2Tx-MnO2-0.5/TPU;(e) Ti3C2Tx-MnO2-1.0/TPU;(f) Ti3C2Tx-MnO2-2.0/TPU
Figure 6. Digital photo of carbon residues of samples after cone calorimeter test: (a) TPU; (b) MnO2/TPU; (c) Ti3C2Tx/TPU; (d) Ti3C2Tx-MnO2-0.5/TPU; (e) Ti3C2Tx-MnO2-1.0/TPU; (f) Ti3C2Tx-MnO2-2.0/TPU
图 8 锥形量热仪测试后TPU纳米复合材料炭渣的SEM图像:((a1), (a2)) TPU;((b1), ( b2)) MnO2/TPU;((c1), (c2)) Ti3C2Tx/TPU;((d1), (d2)) Ti3C2Tx-MnO2-0.5/TPU;((e1), (e2)) Ti3C2Tx-MnO2-1.0/TPU;((f1), (f2)) Ti3C2Tx-MnO2-2.0/TPU
Figure 8. SEM images of carbon residues of TPU nanocomposites after CCT: ((a1), (a2)) TPU; ((b1), (b2)) MnO2/TPU; ((c1), (c2)) Ti3C2Tx/TPU; ((d1), (d2)) Ti3C2Tx-MnO2-0.5/TPU; ((e1), (e2)) Ti3C2Tx-MnO2-1.0/TPU; ((f1), (f2)) Ti3C2Tx-MnO2-2.0/TPU
表 1 TPU纳米复合材料配方表
Table 1. Recipe list of TPU nanocomposites
No. Sample TPU/g Ti3C2Tx-MnO2/g Ti3C2Tx/g MnO2/g 1# TPU 60.000 0.000 0.000 0.000 2# Ti3C2Tx-2.0/TPU 58.800 0.000 1.200 0.000 3# MnO2-2.0/TPU 58.800 0.000 0.000 1.200 4# Ti3C2Tx-MnO2-2.0/TPU 58.800 1.200 0.000 0.000 5# Ti3C2Tx-MnO2-1.0/TPU 59.400 0.600 0.000 0.000 6# Ti3C2Tx-MnO2-0.5/TPU 59.700 0.300 0.000 0.000 表 2 TPU纳米复合材料的热降解行为
Table 2. Thermal degradation behavior of TPU nanocomposites
Sample T−5%/℃ T−50%/℃ Tmax/℃ Residual yield/wt% Step1 Step2 TPU 319.9 392.4 340.3 404.8 5.92 Ti3C2Tx-2.0/TPU 305.9 400.4 329.9 409.6 7.80 MnO2-2.0/TPU 257.1 310.6 275.7 311.6 9.04 Ti3C2Tx-MnO2-2.0/TPU 295.3 376.1 396.0 349.3 11.36 Ti3C2Tx-MnO2-1.0/TPU 296.2 373.2 323.1 378.7 10.51 Ti3C2Tx-MnO2-0.5/TPU 310.1 392.4 344.9 405.5 4.47 Notes: T−5%—Corresponding temperature at 5wt% weight loss; T−50%—Corresponding temperature when the material is reduced to 50wt%; Tmax—Temperature corresponding to the maximum mass loss rate. 表 3 TPU纳米复合材料在热流密度为35 kW/m2的情况下锥形量热仪测试数据
Table 3. Conical calorimeter test data of the TPU nanocomposites under the heat flux of 35 kW/m2
Sample TTI/
sPHRR/
(kW·m−2)THR/
(MJ·m−2)PSPR/
(m2·s−1)TSR/
(m2·m−2)PCOPR/
(g·s−1)PCO2PR/
(g·s−1)CO TY/
(kg·kg−1)CO2 TY/
(kg·kg−1)TPU 63 920 85.6 0.63 9108.4 0.0085 0.50 0.85 49.38 (Error) ±5 ±65 ±9.4 ±0.04 ±1073.6 ±0.0005 ±0.03 ±0.07 ±5.62 Ti3C2Tx-2.0/TPU 55 883 69.1 0.78 7528.6 0.0076 0.48 0.92 39.60 MnO2-2.0/TPU 29 940 66.3 0.95 7447.3 0.0103 0.53 0.53 39.14 Ti3C2Tx-MnO2-0.5/TPU 47 764 61.1 0.45 6576.8 0.0056 0.42 0.56 37.90 Ti3C2Tx-MnO2-1.0/TPU 38 891 68.1 0.44 6065.6 0.0071 0.49 0.61 35.17 Ti3C2Tx-MnO2-2.0/TPU 39 955 61.1 0.39 6285.8 0.0070 0.51 0.66 34.68 Notes: TTI—Time to ignite; PHRR—Peak of heat release rate; THR—Total heat release; PSPR—Peak of smoke production rate; TSR—Total smoke release; PCOPR—Peak of carbon monoxide production rate; PCO2PR—Peak of carbon dioxide production rate; CO TY—Total yield of carbon monoxide; CO2 TY—Total yield of carbon dioxide. -
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