Network structure enabling re-use and near full property retention in CNT sheets recycled from thermoset composites

Resumen

Carbon nanotubes are presently used in batteries, structural composites, and electrical conductors, at a scale of kilotonnes/year. Their use could increase above megatonnes/year as they become available as co -products of turquoise hydrogen and displace CO2-intensive metals. In this work we study the recycling potential of sheets of CNTs, the macroscopic architecture for battery current collectors and for structural laminate composites. We use CNT sheets produced both in our laboratory and commercially to manufacture composites with aerospace -grade epoxy resin through compression moulding. After removal of the polymer phase through pyrolysis, the sheets fully retain their structure and can be re -processed without further treatment. No introduction of chemical or orientational defects is observed. Commercial CNT sheets with areal density of 12-14 g/m2 retain 95 % of their longitudinal strength and 100 % modulus and electrical conductivity. Laboratory -grade sheets with higher alignment retain over 50 % of their strength (54-59 %). This level of property retention enables re -use for the same application, the highest level of recycling potential, which is currently unachievable for carbon fibres recycled in short discontinuous form. It stems from the inherent toughness of the CNT network structure. As a measure of damage tolerance, we evaluate the essential work of fracture of CNT sheets (3.96 kJ/m2 and 69 kJ/m2 for commercial and laboratory -grade, respectively) which is in the range of tough polymers and metals.