Preparation and properties of synergistic flame retardant nylon 66 with aluminium diethyl phosphate and halloysite nanotubes
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摘要: 使用二乙基次磷酸铝(ADP)与埃洛石纳米管(HNTs)作为阻燃体系,采用熔融共混法对尼龙66(PA66)进行阻燃改性,研究了ADP与HNTs的配比对ADP-HNTs/PA66复合材料的阻燃性能、力学性能及热稳定性的影响,对燃烧残炭进行SEM观察,通过TG-IR和FTIR的手段研究阻燃机制。研究发现,ADP-HNTs/PA66复合材料的阻燃性能随HNTs的比例增大而先增高后下降,在阻燃体系为11wt%ADP-1wt%HNTs时,ADP-HNTs/PA66复合材料的UL94阻燃等级为V-0级,极限氧指数(LOI)为35.6%,具有协效阻燃作用;拉伸强度及断裂伸长率随ADP-HNTs阻燃体系中HNTs的比例在一定范围内增大而逐渐增大,冲击强度则逐渐下降;TG分析表明,HNTs能够促进成炭,减缓降解;SEM结果显示,ADP-HNTs阻燃体系能够形成连续致密炭层;TG-IR和FTIR分析表明,ADP兼具气相及凝聚相阻燃,HNTs能够在凝聚相中与ADP产生相互作用,促进交联成炭。Abstract: The flame retardant modification of nylon 66 (PA66) was carried out by melt blending method using aluminium diethyl phosphate (ADP) and halloysite nanotubes (HNTs) as flame retardant system. The effects of the ratio of ADP to HNTs on the flame retardant properties, mechanical properties and thermal stability of ADP-HNTs/PA66 composites were studied. The combustion carbon layer was observed by SEM. The flame retardant mechanism was studied by TG-IR and FTIR. The results show that the flame retardancy of the ADP-HNTs/PA66 composites increases first and then decreases with the increase of the proportion of HNTs. When the flame retardant system is 11wt%ADP-1wt%HNTs, the UL94 flame retardant grade of the ADP-HNTs/PA66 composite is V-0 grade, the limiting oxygen index (LOI) is 35.6%, and it has synergistic flame retardant effect. The tensile strength and elongation at break increase with the increase of the proportion of HNTs in the ADP-HNTs flame retardant system, while the impact strength decreases gradually. TG analysis shows that HNTs can promote charring and slow down the degradation. SEM shows that ADP-HNTs flame retardant system can form a continuous dense carbon layer. TG-IR and FTIR analysis show that ADP has both gas phase and condensed phase flame retardancy, and the introduction of HNTs can interact with ADP in the condensed phase to promote cross-linking and charring.
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图 5 12wt%ADP/PA66(S1)及10wt%ADP-2wt%HNTs/PA66(S3)燃烧前后的FTIR图谱
Figure 5. FTIR spectra of 12wt%ADP/PA66 (S1) and 10wt%ADP-2wt%HNTs/PA66 (S3) before and after combustion ((a) 12wt%ADP/PA66 (S1) before combustion; (b) 12wt%ADP/PA66(S1) residual char; (c) 10wt%ADP-2wt%HNTs/PA66 (S3) before combustion; (d)10wt%ADP-2wt%HNTs/PA66 (S3) residual char)
表 1 ADP-HNTs/尼龙66(PA66)复合材料配方
Table 1. Formulation of ADP-HNTs/nylon 66 (PA66) composites
No. Mass fraction/wt% PA66 ADP HNTs Antioxidants S0 100 0 0 0.0 S1 87.5 12 0 0.5 S2 87.5 11 1 0.5 S3 87.5 10 2 0.5 S4 87.5 9 3 0.5 S5 87.5 8 4 0.5 S6 86.5 10 3 0.5 S7 85.5 10 4 0.5 表 2 ADP-HNTs/PA66复合材料的垂直燃烧(UL94)及极限氧指数(LOI)测试结果
Table 2. Vertical burning test (UL94) and limit oxygen index (LOI) test results of ADP-HNTs/PA66 composites
No. UL 94 LOI/% 3.2 mm Dripping 1.6 mm Dripping S0 V-2 Yes NR Yes 24.5 S1 V-1 No V-2 Yes 33.3 S2 V-0 No V-0 No 35.6 S3 V-0 No V-0 No 33.8 S4 V-0 No V-2 Yes 33.2 S5 V-2 Yes V-2 Yes 32.0 Note:NR—No rating. 表 3 ADP-HNTs/PA66复合材料的力学性能
Table 3. Mechanical properties of ADP-HNTs/PA66 composites
No. Tensile strength/MPa Elongation at break/% Impact strength/(kJ·m−2) S0 68.1 53.5 7.0 S1 63.5 10.6 4.0 S2 65.9 13.3 3.9 S3 68.2 24.7 3.8 S4 70.2 22.1 3.6 S5 69.6 19.0 3.0 S6 68.2 24.7 3.8 S7 68.8 26.5 3.4 -
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