Preparation and properties of silicone/phenolic hybrid aerogel

doi:10.11949/0438-1157.20230500

Abstract

Abstract:

The inherent brittleness of phenolic aerogels limits its application in the fields of adsorption and heat insulation. In this study, silicone solution was prepared by using 3-aminopropyltriethoxysilane and terephthalaldehyde, which is mixed with the solution of thermoplastic phenolic resin and hexamethylene tetramine, solving the compatibility problem between the two systems through chemical bonding, and sol-gel reaction and ambient pressure drying were carried out to obtain the silicone/phenolic hybrid aerogel. Due to both the introduction of flexible silicone molecular chains and the effect of smaller gel particle size, the brittleness of phenolic aerogel is overcome. The results indicate that obtained hybrid aerogel possesses nanoscale gel network structure, and has a low density of 0.187 g/cm³ and a low room-temperature thermal conductivity of 0.035 W/(m·K). Besides, the hybrid aerogel can better dissipate the stress instead of experiencing brittle fractures under compressive stress. The modulus of the hybrid aerogel is as low as 13.92 MPa, 46% lower than that of phenolic aerogel. This hybrid aerogel prepared with a facile and efficient method is of promising application prospects.

Key words: phenolic, silicone, aerogel, mechanical, insulation

摘要：

酚醛气凝胶的本征脆性限制了其在吸附、隔热等领域的应用。以3-氨丙基三乙氧基硅烷和对苯二甲醛配制有机硅溶液，将其与热塑型酚醛树脂-六亚甲基四胺溶液混合，利用化学键作用解决了两体系的相容性问题，再经溶胶-凝胶反应和常压干燥工艺制备有机硅/酚醛杂化气凝胶。由于韧性有机硅分子链的引入和较小凝胶颗粒尺寸的效应，改善了酚醛气凝胶的脆性。研究结果表明，杂化气凝胶具有纳米级凝胶网络结构，表现出较低的密度（0.187 g/cm³）和室温热导率[0.035 W/(m·K)]；在压缩应力作用下，杂化气凝胶能够更好地耗散应力而未发生脆性断裂，其压缩模量低至13.92 MPa，相较于纯酚醛气凝胶降低了46%。这种通过简易高效方法制备的杂化气凝胶具有广阔的应用前景。

关键词: 酚醛树脂, 有机硅, 气凝胶, 力学性能, 隔热性能

CLC Number:

TB 303

Wenjie XU, Xianfeng JIA, Jitong WANG, Wenming QIAO, Licheng LING, Renping WANG, Zijian YU, Yinxu ZHANG. Preparation and properties of silicone/phenolic hybrid aerogel[J]. CIESC Journal, 2023, 74(8): 3572-3583.

徐文杰, 贾献峰, 王际童, 乔文明, 凌立成, 王任平, 余子舰, 张寅旭. 有机硅/酚醛杂化气凝胶的制备和性能研究[J]. 化工学报, 2023, 74(8): 3572-3583.

Figures/Tables 10

Fig.1 Preparation process, reaction mechanism and digital photographs of Si/PR hybrid aerogel

Table 1 Volume shrinkage and density of representative Si/PR hybrid aerogel samples

Samples	Volume shrinkage/%	Density/(g/cm³)
Si/PR-0	3.7	0.170
Si/PR-25	4.2	0.187
Si/PR-50	7.9	0.242
Si/PR-75	8.6	0.293
Si/PR-100	9.6	0.327

Fig.2 XPS spectrum and FT-IR spectra of Si/PR hybrid aerogel

Fig.3 SEM photographs, particle size distribution and N2 adsorption-desorption isotherms of Si/PR hybrid aerogel

Table 2 Textural characteristics of Si/PR hybrid aerogel sample

Samples	S_BET/ (m²/g)	S_meso/(m²/g)	V_total/(cm³/g)	V_mic/(cm³/g)	V_meso/(cm³/g)	Porosity/%
Si/PR-0	12.56	10.28	0.03	0	0.03	99.49
Si/PR-25	48.63	27.93	0.10	0	0.10	98.13
Si/PR-50	69.72	49.43	0.19	0	0.18	95.40
Si/PR-75	94.34	75.44	0.27	0	0.26	92.09
Si/PR-100	127.47	81.20	0.30	0.01	0.29	90.19

Fig.4 Elemental mapping images of the representative Si/PR hybrid aerogel sample

Fig.5 TG curves and DTG curves of Si/PR hybrid aerogel samples

Fig.6 Characterization of compressive mechanical properties of Si/PR hybrid aerogel

Fig.7 Schematic diagram of the toughening mechanism

Fig.8 Schematic diagram of the heat insulation mechanism and room-temperature thermal conductivities of Si/PR hybrid aerogels

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