Micro and nanostructured carbon-phenolic ablators modified by PVP addition

Abstract

Carbon-phenolic ablators can efficiently protect space vehicles from the extreme temperatures typical of the reentry phase in a planet’s atmosphere. Their performances are attributed to the low thermal conductivity and to the decomposition of the phenolic resin. These phenomena are strongly influenced by the materials microstructure. In the present work, standard and polyvinylpyrrolidone (PVP)-modified carbon-phenolic ablators were manufactured and characterized: the influence of PVP on the final microstructure and chemistry of the ablators was studied through SEM-EDS, X-ray Microscopy (XRM) analysis and FTIR technique; the mechanical properties were evaluated through compression tests on virgin and charred samples while ablative performance of the ablators were evaluated with an oxyacetylene flame exposure test. Weak bonds between phenolic resin chains and PVP were observed. The microstructure of the ablators, both before and after the exposure to the oxyacetylene flame, is strongly influenced by the PVP addition, furthermore the addition of 10 and 20 %wt of PVP can guarantee a reduction of about 30 % of the back temperature during the oxyacetylene flame test with respect to the standard carbon-phenolic ablator. Compression tests on the manufactured ablators enlighten also an improvement in the mechanical properties for PVP-enriched ablators, in particular considering their charred state.