Effect of flux agents on properties of ceramifiable flame retardant room temperature vulcanized silicone rubber foam
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摘要: 为提升室温硫化硅橡胶泡沫的阻燃性能和耐火性能,本文以不同熔点玻璃粉和硼酸锌为助熔剂,云母粉为耐火填料,制备可陶瓷化阻燃室温硫化硅橡胶泡沫,并研究了不同无机填料种类和配比对硅橡胶泡沫微观形貌、热稳定性、阻燃性能和燃烧行为的影响及不同温度烧蚀下硅橡胶泡沫的陶瓷化行为。结果表明,玻璃粉的引入影响了硅橡胶泡沫的发泡过程,形成了孔径较大的泡沫结构,不利于硅橡胶泡沫阻燃性能、热稳定性、火安全性的提升,但在烧蚀实验中,其能够显著降低硅橡胶泡沫的陶瓷化温度;硼酸锌的引入能够显著提升硅橡胶泡沫的阻燃性能、高温区热稳定性和火安全性,并且硼酸锌与云母粉展现出较好的协同阻燃作用,硅橡胶泡沫的LOI最高达到33.2%,并通过垂直燃烧V-0级,热重分析测试中900℃时的残炭含量最高可达75.9%,硅橡胶泡沫的热释放和烟释放以及烧蚀实验后的质量损失率均得到明显降低,同时,硼酸锌还有助于形成陶瓷状残炭。Abstract: In order to improve the flame retardancy and fire resistance of room temperature vulcanized (RTV) silicone rubber foam, glass powder and zinc borate as flux agent, and mica powder as refractory filler were used to prepare ceramifiable flame retardant RTV silicone rubber foam. The effects of different types and proportions of inorganic fillers on the micromorphology, thermal stability, flame retardancy and combustion behavior of the silicone rubber foam, as well as the ceramifiable behavior of the silicone rubber foam after ablation at different temperatures were studied. The results show that the introduction of glass powder affects the foaming process of the silicone rubber foam, forming a foam structure with large pore size, which is not conducive to the improvement of the flame retardancy, thermal stability and fire safety performances of the silicone rubber foam. But, glass power can remarkably decrease ceramization temperature of the silicone rubber foam. The introduction of zinc borate greatly improves the flame retardancy, thermal stability in high temperature zone and fire safety performances of the silicone rubber foam. Meanwhile, zinc borate and mica powder show good synergistic flame retardant effect. LOI value of the silicone rubber foam can reach to 33.2, and it can pass the vertical combustion V-0 level. Carbon residue of the silicone rubber foam at 900oC can reach up to 75.9% in thermogravimetric analysis. The heat release, smoke release of the silicone rubber foam and the mass loss after the ablation experiment are significantly reduced. In addition, zinc borate also contributes to the formation of ceramic carbon residue.
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Key words:
- RTV silicone rubber foam /
- flux agent /
- flame retardancy /
- combustion behavior /
- ceramifiable property
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表 1 可陶瓷化阻燃室温硫化硅橡胶泡沫的配方及LOI、UL-94测试结果
Table 1. Formulation, LOI and UL-94 test results of the ceramifiable flame retardant RTV silicone rubber foam
Sample Mass ratio Melting point of GP/oC LOI
/wt%UL-94 SRF/wt% GP/wt% ZB/wt% MP/wt% SF 100 0 0 0 − 23.4 NR SF/MP30 70 0 0 30 − 31.8 V-0 SF/GP40010MP20 70 10 0 20 400 23.4 NR SF/GP40015MP15 70 15 0 15 400 24.6 NR SF/GP40020MP10 70 20 0 10 400 23.4 NR SF/GP50020MP10 70 20 0 10 500 24.0 NR SF/GP65020MP10 70 20 0 10 650 22.8 NR SF/GP40030 70 30 0 0 400 26.4 NR SF/ZB10MP20 70 0 10 20 − 33.2 V-0 SF/ZB15MP15 70 0 15 15 − 31.8 V-0 SF/ZB20MP10 70 0 20 10 − 31.0 V-0 SF/ZB30 70 0 30 0 − 31.6 V-0 表 2 可陶瓷化阻燃室温硫化硅橡胶泡沫氮气氛下的热重测试具体数据
Table 2. TGA parameters of the ceramifiable flame retardant RTV silicone rubber foam under N2 atmosphere
Sample Tonset /℃ Tmax /℃ dW/dT/
(%·min−1)Residue /% SF 442.0 576.0 6.36 40.1 SF/MP30 451.7 510.8 2.24 73.0 SF/GP40010MP20 434.9 566.2 6.75 52.8 SF/GP40015MP15 441.4 559.4 10.20 47.5 SF/GP40020MP10 425.2 532.8 7.44 50.4 SF/GP50020MP10 449.7 557.3 10.41 43.7 SF/GP65020MP10 415.8 482.2 11.14 47.7 SF/GP40030 451.6 518.5 20.71 36.4 SF/ZB10MP20 406.2 467.9 2.74 62.9 SF/ZB15MP15 407.7 422.1 1.39 75.9 SF/ZB20MP10 419.1 463.6 1.28 75.0 SF/ZB30 418.4 421.8 1.14 74.1 Notes:Tonset, Tmax and dW/dT are the onset thermal decomposition temperature, the maximum thermal decomposition temperature and the thermal decomposition rate at the Tmax. 表 3 可陶瓷化阻燃室温硫化硅橡胶泡沫空气氛下的热重测试具体数据
Table 3. TGA parameters of the ceramifiable flame retardant RTV silicone rubber foam under air atmosphere
Sample Tonset/℃ Tmax/℃ dW/dT/
(%·min−1)Residue/% SF 354.4 362.0 9.81 56.9 SF/MP30 378.5 380.7 5.65 76.0 SF/GP40010MP20 377.0 509.3 11.91 52.2 SF/GP40015MP15 375.3 507.5 14.39 46.0 SF/GP40020MP10 373.7 498.9 15.64 42.1 SF/GP50020MP10 363.3 367.2 6.65 64.1 SF/GP65020MP10 376.5 452.8 17.03 42.4 SF/GP40030 369.6 495.8 16.60 40.6 SF/ZB10MP20 374.4 372.3 4.91 80.2 SF/ZB15MP15 379.8 551.9 3.91 73.0 SF/ZB20MP10 376.4 370.5 3.69 79.5 SF/ZB30 367.7 362.1 3.82 81.2 表 4 可陶瓷化阻燃室温硫化硅橡胶泡沫的锥形量热测试主要数据
Table 4. Burning parameters of the ceramifiable flame retardant RTV silicone rubber foam in cone calorimeter test
Sample TTI
/sPHRR
/(kW·m−2)THR
/(MJ·m−2)TTPHRR
/sTSP
/m−2Residue
/%SF 7 145.0 40.0 170 18.3 52.6 SF/MP30 13 76.6 23.0 30 1.7 79.6 SF/GP40010MP20 15 117.9 35.7 35 16.7 68.3 SF/GP40015MP15 23 133.5 47.7 45 17.6 65.4 SF/GP40020MP10 24 130.7 42.0 45 17.0 60.2 SF/GP50020MP10 14 98.6 36.3 40 11.8 69.2 SF/GP65020MP10 50 167.6 96.0 70 49.5 71.4 SF/GP40030 33 154.0 65.6 50 26.9 66.2 SF/ZB10MP20 16 84.5 25.8 35 3.4 81.8 SF/ZB15MP15 16 73.4 24.5 35 3.2 75.7 SF/ZB20MP10 10 72.2 29.1 30 4.8 81.6 SF/ZB30 14 80.1 30.7 35 7.1 80.5 Notes:TTI, PHRR, THR, TTPHRR and TSP are time to ignition, peak of heat release rate, total heat release, time to PHRR and total smoke production. 表 5 可陶瓷化阻燃室温硫化硅橡胶泡沫烧蚀后质量损失率
Table 5. Mass loss rate of the ceramifiable flame retardant RTV silicone rubber foam after ablation
Sample Mass loss/% 600oC 800oC 1000oC SF 89.16 75.71 80.33 SF/MP30 45.56 20.45 17.65 SF/GP40010MP20 66.73 67.18 67.52 SF/GP40015MP15 66.02 65.72 64.43 SF/GP40020MP10 62.60 69.52 62.12 SF/GP50020MP10 67.49 66.32 61.66 SF/GP65020MP10 59.73 47.85 51.40 SF/GP40030 64.30 54.52 50.00 SF/ZB10MP20 53.45 32.78 25.61 SF/ZB15MP15 52.07 48.19 26.45 SF/ZB20MP10 35.56 31.63 30.00 SF/ZB30 59.39 35.48 43.35 -
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