This study was conducted to improve the adhesion strength between a propellant, liner, and heat‐resistant material. As the drying time of the heat‐resistant material increased, the adhesion strength between the propellant, liner, and heat‐resistant material improved. Further, the surface of the heat‐resistant material was subjected to buffing treatment to improve the adhesion strength. In addition, as the thickness of the heat‐resistant material increased, the adhesion strength degraded. Moreover, the adhesion strength was improved by increasing the thickness of the liner on the heat‐resistant material. Besides, the adhesion strength slightly reduced with an increase in the plasticizer content. The liner curing time was an important factor affecting the adhesion strength, and an optimum liner curing time was obtained. In this study, the adhesion strength was improved by applying a barrier coat between the heat‐resistant material and liner. The adhesion was further improved when the heat‐resistant material was buffed.

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This study demonstrates the utility of thermo-regulated phase separable alumina/camphene suspensions containing poly(methyl methacrylate) (PMMA) microspheres as porogens for the production of multi-scale porosity structures. The homogeneous suspension prepared at 60 °C could undergo phase separation during freezing at room temperature. This process resulted in the 3D networks of camphene crystals and alumina walls containing PMMA microspheres. As a consequence, relatively large dendritic pores with several tens of microns size could be created as the replica of frozen camphene crystals. In addition, after the removal of PMMA microspheres via heat-treatment, micron-sized small spherical pores could be generated in alumina walls. As the PMMA content with respect to the alumina content increased from 0 vol% to 40 vol%, while the camphene content in the suspensions was kept constant (70 vol%), the overall porosity increased from 45.7 ± 0.5 vol% to 71.4 ± 0.5 vol%. This increase in porosity is attributed to an increase in the fraction of spherical pores in the alumina walls. Thus, compressive strength decreased from 153 ± 18.3 MPa to 33 ± 7.2 MPa. In addition, multi-scale porosity alumina objects with a honeycomb structure comprising periodic hexagonal macrochannels surrounded by dual-scale porosity walls were constructed using a 3D plotting technique.

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