Highly filled organoclay/phenolic resin nanocomposite as an ablative heat shield material

摘要

The successful return of space vehicles to the Earth's atmosphere depends largely on the provision made for reducing the aerodynamic heat transfer to its structure. Regarding this, using charring ablative composites is more effective and economic than other methods. Some limitations are associated with the ablative composites, such as weakness of composite char structure which results in easy mechanical corrosion leading to faster surface erosion of insulator. Polymer nanocomposites, especially highly filled systems, show interesting mechanical and thermal properties. In this work, high-filled organoclay/asbestos/phenolic nanocomposite samples were prepared as prototypes. The morphology, mechanical and ablation performance of these nanocomposites were investigated and compared with those of their composite counterparts. Furthermore, toughening mechanism of such highly filled nanocomposite system was studied and its capability as ablative heat shield was discussed. The results showed that the ablation performance of the highly filled polymeric nanocomposite, with exfoliated morphology, was higher than that of the composite counterpart; up to 35 % reduction in erosion rate and above 300 % decrease in temperature in depth. These nanocomposites preserved their strength and modulus in spite of high loading of clay and showed higher toughening in comparison with composite counterpart. The toughening mechanism of the highly filled polymeric nanocomposite was distinguished as crack branching due to flake shape and strength of organoclay platelets.