Co-polyimide aerogel using aromatic monomers and aliphatic monomers as mixing diamines

Polyimide aerogels are promising for diverse applications owing to their nano-porous structure and superior properties. However, the shrinkage of melamine-crosslinked polyimide (MPI) aerogels has greatly compromised their performance in practical applications. In this study, supercritical drying with ethanol rather than CO 2 is employed to enhance their in-use shape stability at high temperatures. The structure, thermal insulation, mechanical strength of the resultant aerogels as well as their shape stability are characterized. Experimental results reveal that the shape stability of MPI aerogels during use is greatly improved thanks to the in-advance baptism of supercritical ethanol drying. The aerogel shrinks by only 2.64 vol.% after being treated at 280 °C for 72 h. Besides, the MPI aerogel shows enhanced compressive strength and can easily support a load more than 20 000 times its own weight. The thermal conductivity of these aerogels varies from 0.034 to 0.046 W m −1 k −1 , indicative of remarkable performance in thermal insulation. In addition, the aerogels that started to decompose at as high as 500 °C also perform well in thermal stability and char forming. It can be envisaged that the developed MPI aerogels with greatly improved in-use shape stability may have broad prospects for thermal insulation at high temperatures.

Section: Thermal Propertiesmentioning

confidence: 85%

Melamine‐Crosslinked Polyimide Aerogels from Supercritical Ethanol Drying with Improved In‐Use Shape Stability Against Shrinking

Chen

Liu

Sun

et al. 2021

“…With respect to its nanostructure configuration, the fabricated double backbone aerogel (S4) presented very low thermal conductivity of 19.7 mW mK −1 , which shows about 40% decrease over previously studied polyimide aerogels. [ 17,18 ] Furthermore, this double backbone aerogel presented enhanced mechanical compression resistance at relatively low density of 0.068 g cm −3 , with measured compression modulus of 1.64 MPa. Double backbone polyimide aerogels with high service temperature, high thermal insulation, and improved mechanical properties can be used as light in weight thermal insulation layer of firefighting gears as well as in other applications such as triboelectric nanogenerator (TENG) for self‐powered and wearable sensor applications in extreme temperature environments.…”

Section: Introductionmentioning

confidence: 97%

“…[ 13,16 ] However, from the previous studies, unlike silica aerogels with low effective thermal conductivity of about 20 mW mK −1 , polyimides present higher thermal conductivity ranging from 30 to 50 mW mK −1 , which is comparable to significantly cheaper insulation materials such as micro porous polyurethane foams. [ 17,18 ] Based on this, enhanced ductility and suitable service temperature of the polyimide aerogels suggests their potential to be used as insulation material for high‐temperature applications such as firefighting gears. Yet, they still require further improvement in their thermal insulation while maintaining suitable physical and mechanical properties.…”

Section: Introductionmentioning

confidence: 99%

Double Dianhydride Backbone Polyimide Aerogels with Enhanced Thermal Insulation for High‐Temperature Applications

Mosanenzadeh

Alshrah

Saadatnia

et al. 2020

Aerogels owe their high thermal insulation and other unique properties to their nanostructure configuration. However, controlling the aerogels' morphology is always a scientific challenge. In this study, double dianhydride backbone (double backbone) polyimide aerogels with tailored nanostructure assembly are created for the first time. This is achieved by controlled polymerization reaction of oligomers with distinct dianhydride monomers. Combining the two oligomers through a controlled polymerization reaction is a successful strategy for tailoring the aerogels nanostructure assembly as well as other properties. The fabricated double backbone aerogel presents 40% reduced thermal conductivity of 19.7 mW mK−1 over previously studied polyimide aerogels along with the compression modulus of 1.64 MPa at a relatively low density of 0.068 g cm−3. Such low thermal conductivity is comparable with the inorganic counterparts. Light in weight and high thermally insulated polyimide aerogels with suitable mechanical properties and high service temperature are an appropriate replacement for current fireproof insulation materials.

“…The last region is a densification region at high strain (>45%), in which the stress increases steeply and the hardening behavior occurs. [ 41–44 ] All the samples have a certain degree of elasticity, while the rebound rate of PP‐7 is significantly higher than that of PP‐0. This is due to the presence of a large number of methyl groups on the aerogel skeleton.…”

Section: Resultsmentioning

confidence: 99%

Moisture‐Resistant and Mechanically Strong Polyimide‐Polymethylsilsesquioxane Hybrid Aerogels with Tunable Microstructure

Wang

Liu

et al. 2021

Moisture‐resistant and mechanically strong polyimide (PI)‐polymethylsilsesquioxane hybrid aerogels with doubly cross‐linked structures are synthesized through sol–gel technology and supercritical CO2 fluid drying. By using bis(trimethoxysilylpropyl) amine as a cross‐linker, the end‐capped polyamide acid derived from biphenyl‐3,3′,4,4′‐tetracarboxylic dianhydride and 4,4′‐oxydianiline is cross‐linked with a silica network using methyltrimethoxysilane as the silica source precursor. The resultant hybrid aerogels show low density (0.12–0.15 g cm−3), low thermal conductivity (0.032–0.049 W m−1 K−1), high hydrophobicity (125–140°) and good thermal stability (above 435 °C) with tunable microstructure. With the increase of silica sol volume, the microstructure of hybrid aerogels transforms from fibrous network to hierarchical microstructure. Aerogels with high content of silica sol exhibit good moisture resistance, high Young's modulus (Max. 19.6 MPa), and high specific modulus (Max. 131 kN m kg−1), which are attributed to their unique hierarchical microstructure with a sheet skeleton. These hybrid aerogels are promising in the fields of thermal insulation, aerospace applications and so on.