3D Printing of Thermal Insulating Polyimide/Cellulose Nanocrystal Composite Aerogels with Low Dimensional Shrinkage

Abstract

Polyimide (PI)-based aerogels have been widely applied to aviation, automobiles, and thermal insulation because of their high porosity, low density, and excellent thermal insulating ability. However, the fabrication of PI aerogels is still restricted to the traditional molding process, and it is often challenging to prepare high-performance PI aerogels with complex 3D structures. Interestingly, renewable nanomaterials such as cellulose nanocrystals (CNCs) may provide a unique approach for 3D printing, mechanical reinforcement, and shape fidelity of the PI aerogels. Herein, we proposed a facile water-based 3D printable ink with sustainable nanofillers, cellulose nanocrystals (CNCs). Polyamic acid was first mixed with triethylamine to form an aqueous solution of polyamic acid ammonium salts (PAAS). CNCs were then dispersed in the aqueous PAAS solution to form a reversible physical network for direct ink writing (DIW). Further freeze-drying and thermal imidization produced porous PI/CNC composite aerogels with increased mechanical strength. The concentration of CNCs needed for DIW was reduced in the presence of PAAS, potentially because of the depletion effect of the polymer solution. Further analysis suggested that the physical network of CNCs lowered the shrinkage of aerogels during preparation and improved the shape-fidelity of the PI/CNC composite aerogels. In addition, the composite aerogels retained low thermal conductivity and may be used as heat management materials. Overall, our approach successfully utilized CNCs as rheological modifiers and reinforcement to 3D print strong PI/CNC composite aerogels for advanced thermal regulation.

Anisotropic Polyimide/Cellulose Nanofibril Composite Aerogels for Thermal Insulation and Flame Retardancy

“…29 Hence, such structure and property differences between axial and radial directions of anisotropic aerogel materials provide promising candidates for microelectronics, thermal insulation, and electromagnetic interference shielding applications. 27,29,32,40 Nanofillers with low thermal conductivity such as silica, 11,13 glass fiber, 41 cellulose nanocrystal, 42 attapulgite, 43 and halloysite 44 are also incorporated to facilely fabricate heatinsulated PI composite aerogels. However, maintaining low shrinkage and tuning pore morphology remain a recurring challenge in such an area.…”

“…Nanofillers with low thermal conductivity such as silica, , glass fiber, cellulose nanocrystal, attapulgite, and halloysite are also incorporated to facilely fabricate heat-insulated PI composite aerogels. However, maintaining low shrinkage and tuning pore morphology remain a recurring challenge in such an area.…”

Emerging 3D printed thermal insulating materials for sustainable approach: A review and a way forward

“…Figure 5 below represents the two techniques adopted for fabricating various shapes and sizes of samples. This study suggested that SLA and DIW could be used to fabricate efficient thermal insulating polymer composites 49 …”

“…This study suggested that SLA and DIW could be used to fabricate efficient thermal insulating polymer composites. 49 In a recent study, polyamide was used to fabricate 3D-printed gyroid structured objects through selective layer sintering 3D printing. B. Anwajler carried out this experimental work.…”

3D Printing Processability of a Thermally Conductive Compound Based on Carbon Nanofiller-Modified Thermoplastic Polyamide 12

“…Recent advances in multi-material 3D printing present a potential extension of the product design beyond complex geometries, while functional, single-step manufacturing processes can be exploited by utilizing custom composite materials suitable for multifactorial applications. The fused filament fabrication (FFF) technique is of low cost with a large range of feedstock materials suitable for a wide range of 3D printing applications [ 4 , 5 ]. Thermoplastic materials, such as polylactic acid (PLA) and polyamide (PA) [ 6 ], can be melted and extruded as a strand through a nozzle in a line by line and layer by layer manner in FFF, and the extruded material (thermoplastic strands) rapidly solidifies and adheres with the surrounding material, which is especially useful for complex design and advanced functionality of smart products [ 4 , 7 , 8 ].…”