Galactans and cellulose in flax fibres: putative contributions to the tensile strength

The proton spin-spin relaxation time, T2, measured from solid-state NMR, indicates a greater rigidity for cellulose than for the adhesive matrix between the microfibrils of flax ultimate fibres. Cytochemical and biochemical analyses allow the identification of: (1) EDTA-soluble RG I-polymers in the primary walls and cell junctions of fibres; (2) long 1 --> 4-beta-D-galactan chains between primary and secondary wall layers; and (3) arabinogalactan-proteins throughout the secondary walls. These polymers in the adhesive matrix between microfibrils and/or cellulose layers ensure that cracks propagate along the matrix rather than across the fibres and play an important role in allowing flax fibres to approach the tensile strength of advanced synthetic fibres like carbon and Kevlar.