Preparation and characterization of transparent and compressible methylsilsesquioxane aerogels using MTES as precursor

doi:10.16085/j.issn.1000-6613.2019-1080

Abstract

Abstract:

At present, the aerogels prepared from methyltrimethoxysilane mainly use methanol or ethanol as solvent, which has the problems of high preparation cost, poor thermal insulation performance and poor transparency. In order to substantially improve the preparation process and properties of the aerogel, a superhydrophobic compressible methylsilsesquioxane aerogel with high transparency was prepared by replacing the alcohol solvent with water solvent, compatibilizing by surfactant, sol-gel acid-base two-step method and CO₂ supercritical drying method. The influence of the trifunctional silicon source content on the molecular behavior of surfactant cetyltrimethylammonium bromide was analyzed. The results showed that in the aqueous solvent system, the increase of the trifunctional silicon source content could affect the morphology of surfactant micelles, which promoted the skeletal structure of aerogel changing from the uniformly distributed fibrous shape to the densely packed granular shape. In the study of the replacement process, it was found that when a strong alkaline aqueous solution was used instead of the conventional aqueous solution as a replacement liquid, there was a more efficient replacement efficiency, resulting in less residual impurities in the pores. As a result, there was almost no mass loss during thermogravimetric analysis at 0—300℃. The aerogel can be widely applied to the thermal insulation walls of buildings and the insulation layer of windows.

Key words: MTES, CTAB, methylsilsesquioxane silica aerogel, compressible, transparent, superhydrophobic, low thermal conductivity

摘要：

目前利用甲基三乙氧基硅烷制备的气凝胶主要是以甲醇或乙醇为溶剂，存在制备成本高、气凝胶隔热性能和透明度差的问题。为了对该气凝胶制备工艺和性能进行实质性改进，本文以水溶剂代替醇类溶剂，利用表面活性剂的增容作用，结合溶胶-凝胶酸碱两步法以及CO₂超临界干燥法制备得到了具有高透明度的超疏水可压缩的甲基倍半硅氧烷气凝胶，并且对三官能团硅源含量变化影响表面活性剂十六烷基三甲基溴化铵分子行为的内容进行了对比分析。结果表明：在水溶剂体系中，三官能团硅源含量的增加会影响表面活性剂胶束的形态，从而促使气凝胶的骨架结构逐渐由均匀分布的纤维状转变为密集堆积的颗粒状。在对置换工艺的研究中，发现用强碱性水溶液替代传统水溶液作为置换液时会有更加高效的置换效率，使得孔隙中杂质残留较少，以致0～300℃热重分析过程中几乎没有质量损失。该气凝胶可以广泛应用于建筑物的隔热墙和窗户的保温层。

关键词: 甲基三乙氧基硅烷, 十六烷基三甲基溴化铵, 甲基倍半硅氧烷气凝胶, 可压缩性, 透明, 超疏水, 低热导率

CLC Number:

TB321

Xiaohua LI,Zichun YANG,Kunfeng LI,Shuang ZHAO,Zhifang FEI,Zhen ZHANG. Preparation and characterization of transparent and compressible methylsilsesquioxane aerogels using MTES as precursor[J]. Chemical Industry and Engineering Progress, 2020, 39(3): 1115-1121.

李肖华,杨自春,李昆锋,赵爽,费志方,张震. 以MTES为硅源制备透明可压缩的甲基倍半硅氧烷气凝胶及其表征[J]. 化工进展, 2020, 39(3): 1115-1121.

Figures/Tables 12

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样品	MTES /mL	CTAB /g	酸性去离子水 (0.02mol·L^-1) /mL	氨水（6.5mol·L^-1） /mL
M1-1	5	1	30	0.06
M1-2	10	1	30	0.06
M1-3	15	1	30	0.06
M1-4	20	1	30	0.06

样品	MTES /mL	CTAB /g	酸性去离子水 (0.02mol·L^-1) /mL	氨水（6.5mol·L^-1） /mL
M1-1	5	1	30	0.06
M1-2	10	1	30	0.06
M1-3	15	1	30	0.06
M1-4	20	1	30	0.06

样品	密度 /mg·cm^-3	比表面积 /m²·g^-1	平均孔径 /nm	可见光透光率/%	疏水角 /(°)
M1-1	52	682	7.8	56	149
M1-2	75	663.1	9.9	89	151
M1-3	126	581.6	13.3	82	149
M1-4	168	555	13.0	72	150

样品	密度 /mg·cm^-3	比表面积 /m²·g^-1	平均孔径 /nm	可见光透光率/%	疏水角 /(°)
M1-1	52	682	7.8	56	149
M1-2	75	663.1	9.9	89	151
M1-3	126	581.6	13.3	82	149
M1-4	168	555	13.0	72	150

三官能团硅源	MTES气凝胶	MTES在有机溶剂中制备的气凝胶	MTMS在水溶剂中制备的气凝胶	MTMS在有机溶剂中制备的气凝胶
密度/mg·cm^-3	52～168	10^[28]、37～54^[17]	35～247^[21,22]	41～61^[11,23]
热导率/mW·m^-1·K^-1	21～25	38^[27]、56～62^[17]	26～35^[21,22]	36～57^[11,23]