Properties of HNTs modified phenolic composite foams
Properties of carbon foam composites were restricted by their precursor.In order to optimize the precursor of carbon foam composites,halloysite nanotubes(HNTs)modified phe-nolic composite foams were synthesized by compression molding and high-temperature curing treatment,with phenolic microspheres as dispersed phase,phenolic resin as matrix and HNTs as reinforcement.The microstructure,mechanical properties and thermal stability of the phenolic composite foams were characterized by scanning electron microscope(SEM),universal testing machine and thermogravimetric analyzer.The results show that the mechanical strength and frac-ture toughness improved significantly with the introduction of HNTs,due to the fact that phenolic microspheres'phase and HNTs phase effectively hinder crack propagation and consume crack propagation energy.The compressive strength and specific compressive strength achieved the maximum for the phenolic composite foam with 4％HNTs,15.4 MPa and 38.7 MPa·cm3·g-1,respectively,which were 65.6％and 59.3％higher than those of the pure phenolic composite foam.The modified phenolic composite foams showed good thermal stability.Their initial decom-position temperatures were all above 350 ℃.Because of the slow release of HNTs on the decom-position of the resin matrix and heat transfer,their carbon residue rates were more than 60.8％at 800 ℃,and even reached up to 68.3％.The current research of HNTs modified phenolic com-posite foams was helpful to improving comprehensive properties of carbon foams,which contrib-ute a lot to the application of carbon foams in the aerospace field.
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