Flame retardant epoxy resins and glass fiber reinforced epoxy composites synergistically modified by ammonium polyphosphate, melamine and triazine carbon-forming agent
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摘要: 采用聚磷酸铵(APP)与不同比例三聚氰胺(MA)和三嗪成炭剂(CFA)复配对环氧树脂进行阻燃改性。系统研究了不同配比阻燃剂(总量保持40wt%)的加入对环氧树脂流变特性、固化行为、热机械性能、力学性能及阻燃性能的影响。将优化后的阻燃改性环氧树脂用于制备玻璃纤维增强环氧树脂复合材料(GFRC),对并其力学和阻燃性能进行了研究。结果表明,APP单独与MA或CFA复配改性环氧树脂并未表现出明显的协同阻燃效应,但它们组成的三元复配阻燃体系(30wt%APP-5wt%MA-5wt%CFA)具有良好的协同阻燃效应。相比未改性环氧树脂,APP-MA-CFA改性环氧树脂的极限氧指数(LOI)由18.0%提高到了50.2%,热释放峰值速率(PHRR)下降了84%,总热释放量(THR)下降了78%。树脂基体中加入阻燃剂后,GFRC的力学性能有所下降,尤其是层间剪切强度。同样地,基于APP-MA-CFA复配改性环氧树脂的GFRC表现出最佳阻燃性能,相比未改性的GFRC,其LOI值由22.8%提高到了66.0%,PHRR由354 kW/m2下降到93 kW/m2,THR由49.3 MJ/m2下降到22.8 MJ/m2。Abstract: Epoxy resins were modified by ammonium polyphosphate (APP) and its combination with different contents of melamine (MA) and triazine carbon-forming agent (CFA). The effects of flame retardants with different proportions(total content of 40wt%) on the rheological, curing, thermomechanical, mechanical and flame-retardant properties of epoxy resins were investigated systematically. The optimized flameretardant epoxy resin was used to fabricate glass fiber reinforced epoxy composite (GFRC), and the mechanical as well as flame retardancy of the resulting GFRC were studied. The results show that the epoxy resins modified by APP-MA and APP-CFA combinations do not show apparent synergistic flame retardancy effects, but the ternary APP-MA-CFA system (30wt%APP-5wt% MA-5wt%CFA) demonstrates superior synergistic flame retardancy effects. Compared with the unmodified epoxy resin, the epoxy resin modified by APP-MA-CFA exhibits an increase in limit oxygen index (LOI) from 18% to 50.2%, a 84% decrease in peak heat release rate (PHRR) and a 78% decrease in total hear release (THR). With the addition of flame retardants in the epoxy matrix, the GFRC shows deteriorative mechanical properties, especially for interlaminar shear strength. Again, the GFRC based on the epoxy matrix modified by APP-MA-CFA presents the best flame-retardant performance. Compared with the unmodified GFRC, the modified GFRC shows an increased LOI (from 22.8% to 66.0%), a decreased PHRR (from 354 kW/m2 to 93 kW/m2) and a decreased THR (from 49.3 MJ/m2 to 22.8 MJ/m2).
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图 7 40APP/EP (a)和30APP-5MA-CFA/EP (b)试样燃烧后照片;未改性环氧树脂((c)、(d))、40APP((e)、(f))和30APP-5MA-CF/EP ((g)、(h))试样燃烧后残炭在500和2 000倍下SEM图像
Figure 7. Images of 40APP/EP (a) and 30APP-5MA-CFA/EP (b) after combustion;SEM images of char residues after combustion for unmodified epoxy ((c), (d)), 40APP/EP ((e), (f)) and 30APP-5MA-CFA/EP ((g), (h)) at 500 and 2000 magnification
表 1 未改性和阻燃改性环氧树脂组成配方
Table 1. Formulations of unmodified and flame retardant modified epoxy resins
Sample EP828/wt% Neopentyl diglycidyl ether/wt% HTDA/wt% APP/wt% MA/wt% CFA/wt% Neat 30 20 10 0 0 0 20APP/EP 30 20 10 15 0 0 30APP/EP 30 20 10 26 0 0 40APP/EP 30 20 10 40 0 0 35APP-5MA/EP 30 20 10 35 5 0 30APP-10MA/EP 30 20 10 30 10 0 35APP-5CFA/EP 30 20 10 35 0 5 30APP-10CFA/EP 30 20 10 30 0 10 30APP-5MA-5CFA/EP 30 20 10 30 5 5 Notes: EP—Epoxy; HTDA—Methyl cyclohexandiamine; APP—Ammonium polyphosphate; MA—melamine; CFA—Triazine carbon-forming agent. 表 2 不同含量APP改性环氧树脂的极限氧指数(LOI)和UL-94测试结果
Table 2. Limiting oxygen index (LOI) and UL-94 rating of epoxy resins with different APP contents
Sample LOI/% UL-94 Neat 18.0 No rating 20APP/EP 34.0 V0 30APP/EP 36.5 V0 40APP/EP 47.3 V0 表 3 未改性和阻燃改性环氧树脂的DSC和动态力学分析测试数据
Table 3. DSC and dynamic mechanic alanalysis data of unmodified and flame retardant modified epoxy resins
Sample ΔH/(J.g−1) Ti/℃ Tp/℃ Storage modulus
at 30℃/MPaTg/℃ Neat 446 52 106 2675 94 40APP/EP 290 58 122 4064 108 35APP-5MA/EP 295 50 116 3854 108 30APP-10MA/EP 293 46 117 3651 107 35APP-5CFA/EP 283 53 109 3802 111 30APP-10CFA/EP 287 50 116 3458 110 30APP-5MA-5CFA/EP 275 52 110 3639 110 Notes: ΔH—Enthalpy change of curingreaction; Ti—Initial curing temperature; Tp—Peak temperature; Tg—Glass transition temperature. 表 4 未改性和阻燃改性环氧树脂的LOI和UL-94测试结果
Table 4. LOI and UL-94 rating of unmodified and flame retardant modified epoxy resins
Sample LOI/% UL-94 Neat 18.0 No rating 40APP/EP 47.3 V0 35APP-5MA/EP 46.1 V0 30APP-10MA/EP 47.6 V0 35APP-5CFA/EP 46.7 V0 30APP-10CFA/EP 48.9 V0 30APP-5MA-CFA/EP 50.2 V0 表 5 未改性和阻燃改性环氧树脂的锥形量热测试数据
Table 5. Data of cone calorimeter tests for unmodified and flame retardant modified epoxy resins
Sample PHRR/(kW·m−2) THR/(MJ·m−2) av-ECH/(MJ·kg−1) av-CO/(kg·kg−1) av-CO2/(kg·kg−1) Mass loss/% Neat 1 055 107.0 18.30 0.21 1.99 98.6 40APP/EP 200 26.2 2.50 0.049 0.64 58.9 35APP-5MA/EP 211 27.5 2.33 0.035 0.52 61.5 30APP-10MA/EP 194 25.8 1.88 0.036 0.49 67.3 35APP-/5CFA/EP 249 27.0 4.37 0.051 0.61 40.3 30APP-10CFA/EP 192 25.0 2.06 0.035 0.50 61.3 30APP-5MA-CFA/EP 172 24.0 1.52 0.031 0.42 44.5 Notes: PHRR—Peak heat release rate; THR—Total heat release;av-ECH—Average effective heat of combustion;av-CO—Average release rate of CO;av-CO2—Average release rate of CO2. 表 6 未改性和阻燃改性玻璃纤维增强环氧树脂复合材料(GFRC)的LOI、UL-94和锥形量热测试数据
Table 6. LOI, UL-94 rating and data of cone calorimeter tests for unmodified and flame retardant modified GFRC
Sample LOI/% UL-94 PHRR/(kW·m−2) THR/(MJ·m−2) Neat 22.8 No rating 354 49.3 40APP/EP 56.0 V0 114 31.2 30APP-5MA-5CFA/EP 66.0 V0 93 22.8 -
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