Studies on toughening modification and the properties of phenolic resin by carbon nanotubes in collaboration with hexamethylenetetramine
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摘要: 传统热固性酚醛树脂脆性大,本文采用六亚甲基四胺(HMTA)对酚醛树脂进行了化学增韧改性,并考察了碳纳米管协同改性提高酚醛树脂耐热性能的综合效应。研究发现,不同含量HMTA对酚醛树脂力学性能影响规律呈先增长后下降趋势,2.5wt%HMTA改性酚醛的力学性能最为突出,其压缩强度达到393 MPa,弯曲强度为149 MPa,相比未改性酚醛树脂分别提升24%与62%,断口分析表明增韧体系中形成的“海-岛”结构显著提升了树脂基体的力学性能。但是,HMTA导致酚醛树脂的耐热性能明显下降,在2.5wt%HMTA增韧酚醛体系中加入碳纳米管可将树脂体系的Td5提升至初始酚醛树脂的水平,同时兼具优异的增韧后力学性能。这一结果对结构/防热一体化新型酚醛树脂基体的设计研制具有重要参考价值。Abstract: The conventional thermosetting phenolic resin exhibits significant brittleness. This paper utilized hexamethylenetetramine (HMTA) to chemically toughen phenolic resins. And the comprehensive effect of carbon nanotube synergistic modification on improving the heat-resistant properties of the phenolic resin was also examined. The results indicate that the mechanical properties of the HMTA-modified phenolic resin present a tendency of first increasing and then decreasing with the increase of the HMTA content. The highest mechanical properties are observed in the modified phenolic resin with 2.5wt% HMTA, as its compression strength reaches up to 393 MPa and the bending strength up to 149 MPa, representing increases of 24% and 62%, respectively, compared to the unmodified phenolic resin matrix. The fracture morphology reveals that the low content of HMTA creates numerous "sea-island" structures within the modified phenolic matrix, which significantly contributes to the improvement of the mechanical properties of the phenolic matrix. However, HMTA can lead to an obvious decrease in the heat-resistance of phenolic resins. Adding carbon nanotubes to the 2.5wt% HMTA toughened phenolic system can increase the Td5 of the resin system to the level of the unmodified phenolic resin, while also exhibiting excellent toughened mechanical properties. This lays an important foundation for the design and development of new structural/thermal protection integrated phenolic resin matrices and their composites.
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Key words:
- phenolic resin /
- chemical toughening /
- carbon nanotubes /
- heat resistant performance
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表 1 改性酚醛树脂(PF)的样品名称与组成
Table 1. Nominations and compositions of modified phenolic resins (PF)
Nominations PF/g HMTA/g CNTs/g PF 100 0 0 PF/2.5H 97.5 2.5 0 PF/5.0H 95.0 5.0 0 PF/7.0H 93.0 7.0 0 PF/2.5H-0.25CNTs 97.5 2.5 0.25 PF/2.5H-0.50CNTs 97.5 2.5 0.50 PF/2.5H-0.75CNTs 97.5 2.5 0.75 表 2 不同含量HMTA改性酚醛树脂固化后的热性能参数
Table 2. Thermogravimetric analysis data of cured phenolic resins modified with different contents of HMTA
Designation Td5/℃ Td10/℃ Residue
at 800℃/%PF 362 446 63.8 PF/2.5H 329 430 61.6 PF/5.0H 324 425 60.3 PF/7.0H 304 417 59.5 Notes:Td5 is the pyrolysis temperature at 5% mass loss; Td10 is the pyrolysis temperature at 10% mass loss. 表 3 CNTs与HMTA协同改性酚醛树脂固化后的热性能参数
Table 3. Thermogravimetric analysis data of cured phenolic resins co-modified with CNTs and HMTA
Designation Td5/℃ Td10/℃ Residue
at 800℃/%PF 362 446 63.8 PF/2.5H 329 430 61.6 PF/2.5H-0.25CNTs 380 444 61.8 PF/2.5H-0.50CNTs 392 446 62.5 PF/2.5H-0.75CNTs 394 449 62.9 -
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