A new glassy carbon fibre

Abstract

It is shown that phenol-hexamine polymers may be extruded from the melt to produce fibres which may be carbonised to form fine high-strength glassy carbon fibres with a tensile strength of up to 2 GNm⁻² (300 000 Ib in⁻²) after 900° C heat-treatment. The fibres have a specific modulus of ∼5 Mm compared with ∼14 Mm for carbonised polyacrylonitrile fibres and ∼3 Mm for silica glass fibres. Both strength and modulus increase rapidly with decrease in diameter. The fibres are subjected to no special surface treatment after extrusion but electron microscopy indicates the presence of a thin textured sheath surrounding a true glassy carbon core in the final fibre. The fibres have the advantages of glassy carbon (inertness to chemical attack, resistance to abrasion) and give promise of a new range of cheap high-strength carbon fibres derived from coal tar fractions.