14—RIGIDITY, MOISTURE AND FIBRE STRUCTURE

Abstract

Results are given showing the relation between the modulus of torsional rigidity and moisture regain for ramie, mercerized cotton, Fortisan, viscose rayon, wool and nylon. For all the cellulose fibres, the equation log_e(G/G ₆₅) = — 0·;82[(M/M ₆₅)—1] describes the observed relation between rigidity (G) and moisture regain (M) in terms of the values of these quantities at 65% r.h. The results are analysed on the basis of a two-phase theory of absorption of moisture, originally proposed by Peirce, but modified to take into account the accessibility to moisture of a given fibre. The fall in rigidity with increase in regain is consistent with the idea that this is caused by the breaking of hydrogen bonds between chain molecules in the non-crystalline regions and that, at saturation regain, one molecule of water is bound to each accessible polar group which would otherwise be linked to a similar polar group in a neighbouring chain molecule by means of a hydrogen bond.