Preparation and flame retardancy of thermoplastic polyester elastomer composites
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摘要: 由于热塑性聚酯弹性体(TPEE)极易燃烧,严重阻碍了其在电子电气、电线护套、充电桩等领域的应用,为解决此问题,以二乙基次磷酸铝(AlPi)和三聚氰胺聚磷酸盐(MPP)为阻燃剂,添加到TPEE中,采用密炼和热压成型方法制备出高阻燃性TPEE复合材料。采用极限氧指数(LOI)测试、垂直燃烧(UL-94)测试、锥形量热(CONE)测试等对TPEE复合材料的阻燃性能进行了测试。结果表明:AlPi和MPP复配可以实现TPEE的高效阻燃,添加22wt%复配阻燃剂的TPEE材料的LOI由19.3%提升至31.5%,UL-94达到V-0级,总热释放和峰值热释放速率下降27.6%和64.8%。采用热失重分析仪(TGA)、扫描电子显微镜、力学性能测试仪及电绝缘性能测试仪等对TPEE材料的热稳定性、力学性能、电性能及其烧蚀前后的微观形貌进行了表征。结果表明:复配阻燃剂的阻燃机制为膨胀炭层凝聚相阻隔型阻燃,且促进了TPEE分解成炭;力学性能、电绝缘性能和微观形貌测试表明复配的AlPi和MPP能够提升TPEE材料的电绝缘性,但其与TPEE相容性较差,导致TPEE材料的力学性能下降。Abstract: Thermoplastic polyester elastomer (TPEE) is extremely flammable, which seriously hinders its application in the fields of electronics and electrical, wire sheath, charging station, etc. TPEE composites with high flame retardancy were prepared by adding aluminum diethylphosphinate (AlPi) and melamine polyphosphate (MPP) flame retardant into TPEE matrix through internal mixing and hot pressing process. The flame retardancy of the TPEE composites was studied by limiting oxygen index (LOI), vertical burning (UL-94) and cone calorimeter (CONE) tests. The results show that AlPi combined with MPP can achieve high-efficiency flame retardancy of TPEE composites. In addition, the TPEE composite with 22wt%AlPi and MPP passed the UL-94 V-0 rating and its LOI value increase from 19.3% to 31.5%, accompanied with 27.6% reduction in the total heat release and 64.8% reduction of the peak heat release rate compared to pure TPEE. The thermal stabilities, mechanical properties, and electrical properties of the TPEE composites, as well as the microscopic morphology of the composites before and after ablation were studied by thermogravimetric analyzer (TGA), SEM, universal testing machine and electrical insulation test. The results indicate that the flame retardant mechanism of the composite flame retardant system is the barrier action of intumescent char layer in the condense phase. The composite flame retardant system can promote the decomposition of TPEE into carbon. The mechanical properties, electrical insulation properties and microtopography tests show that the combination of AlPi and MPP can improve the electrical insulation performance, but reduce the mechanical properties of TPEE composites due to their poor compatibility with TPEE matrix.
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图 3 MPP-AlPi/TPEE复合材料的热释放率(HRR) (a)、总热释放(THR) (b)、质量损失率(MLR) (c)和TPEE (d)、3MPP-9AlPi/TPEE (e)、4.25MPP-12.75AlPi/TPEE (f)、5.5MPP-16.5AlPi/TPEE (g)复合材料在锥形量热实验后的残炭照片
Figure 3. Heat release rate (HRR) (a), total heat release (THR) (b), mass loss rate (MLR) (c) of MPP-AlPi/TPEE composite materials and carbon residue photos of TPEE (d), 3MPP-9AlPi/TPEE (e), 4.25MPP-12.75AlPi/TPEE (f) and 5.5MPP-16.5AlPi/TPEE (g) after cone calorimetry test
图 5 TPEE (a)、3MPP-9AlPi/TPEE (b)和5.5MPP-16.5AlPi/TPEE (c)的断面微观形貌及4.25MPP-12.75AlPi/TPEE (d)和5.5MPP-16.5AlPi/TPEE (e)在锥形量热实验后的微观形态
Figure 5. SEM images of shear cross-section microstructure of TPEE (a), 3MPP-9AlPi/TPEE (b), 5.5MPP-16.5AlPi/TPEE (c) and micromorphology of carbon layer of 4.25MPP-12.75AlPi/TPEE (d) and 5.5MPP-16.5AlPi/TPEE (e) after cone calorimetry test
表 1 三聚氰胺聚磷酸盐(MPP)-二乙基次磷酸铝(AlPi)/热塑性聚酯弹性体(TPEE)复合材料的配方
Table 1. Formulations of melamine polyphosphate (MPP)-aluminum diethylphosphinate (AlPi)/thermoplastic polyester elastomer (TPEE) composites
Sample TPEE/wt% AlPi/wt% MPP/wt% TPEE
3MPP-9AlPi/TPEE
4.25MPP-12.75AlPi/TPEE
5.5MPP-16.5AlPi/TPEE100
88
83
780.00
9.00
12.75
16.500.00
3.00
4.25
5.50Note: Each sample contains an additional 2% antioxidant 1010. 表 2 不同MPP-AlPi/TPEE复合材料的极限氧指数(LOI)及垂直燃烧(UL-94)测试结果
Table 2. Limiting oxygen index (LOI) and vertical burning (UL-94) test results of different MPP-AlPi/TPEE composites
Sample LOI/% UL-94 Driping t1/s t2/s TPEE 19.3 No rating Yes —a —a 3MPP-9AlPi/TPEE 26.3 No rating Yes —a —a 4.25MPP-12.75AlPi/TPEE 27.6 V-0 No 2.3 5.7 5.5MPP-16.5AlPi/TPEE 31.5 V-0 No 0.0 1.1 Notes: t1—Self-extinguishing time after the first ignition; t2—Self-extinguishing time after the second ignition; —a: After ignition, the sample continues to burn until it is completely burned out. 表 3 不同MPP-AlPi/TPEE复合材料的锥形量热数据
Table 3. Cone calorimetric data of different MPP-AlPi/TPEE composites
Sample TTI/s Tp/s PHRR/
(kW·m–2)THR/
(MJ·m–2)CO yield/
(kg·kg–1)CO2 yield/
(kg·kg–1)Residue/
%FGI FPI TPEE 33 65 529.0±5.8 41.4±2.6 0.04±0.01 1.82±0.01 4.2±0.1 8.1 0.06 3MPP-9AlPi/TPEE 40 105 277.1±3.2 34.9±2.1 0.18±0.02 1.43±0.02 10.1±0.1 2.6 0.14 4.25MPP-12.75AlPi/TPEE 39 116 260.7±2.8 36.0±2.3 0.21±0.01 1.43±0.01 10.6±0.2 2.3 0.15 5.5MPP-16.5AlPi/TPEE 41 114 186.3±2.4 30.0±1.8 0.20±0.01 1.43±0.01 28.0±0.1 1.6 0.22 Notes: TTI—Ignition time; Tp—Time to reach peak heat release rate; PHRR—Peak heat release rate; FGI—Fire growth index; FPI—Fire performance index. 表 4 MPP-AlPi/TPEE复合材料在空气中的TGA数据
Table 4. TGA data of MPP-AlPi/TPEE composites in air
Sample T5%/℃ Tmax/℃ DTGmax/(%·℃–1) Residue at 700℃ (Exp.)/wt% Residue at 700℃ (Cal.)/wt% TPEE 333.1 393.1 1.9 0.5 — AlPi 435.6 445.6 2.2 24.0 — MPP 351.7 411.1 1.0 21.0 — 3MPP-9AlPi/TPEE 342.1 390.0 1.8 4.1 3.2 4.25MPP-12.75AlPi/TPEE 347.1 391.2 1.7 5.1 4.4 5.5MPP-16.5AlPi/TPEE 348.2 392.2 1.6 7.0 5.5 Notes: T5%—Initial degradation temperature of the composite; Tmax—Temperature at maximum mass loss rate; DTGmax—Maximum mass loss rate; Exp.—Experimental value; Cal.—Calculated value.
表 5 MPP-AlPi/TPEE复合材料的杨氏模量
Table 5. Young's modulus of MPP-AlPi/TPEE composites
Sample Young's modulus/MPa TPEE 4.32±0.23 3MPP-9AlPi/TPEE 4.26±0.26 4.25MPP-12.75AlPi/TPEE 7.01±0.55 5.5MPP-16.5AlPi/TPEE 45.48±1.58 表 6 MPP-AlPi/TPEE复合材料的体积电阻率
Table 6. Volume resistivity of MPP-AlPi/TPEE composites
Sample Volume
resistivity/(1011 Ω·m)TPEE 3.41±0.34 3MPP-9AlPi/TPEE 6.21±0.46 4.25MPP-12.75AlPi/TPEE 8.59±0.57 5.5MPP-16.5AlPi/TPEE 16.90±8.90 -
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