Acylation of silk and wool with acid anhydrides and preparation of water-repellent fibres

Silk and wool fibers were acylated with dodecenylsuccinic anhydride (DDSA) and octadecenylsuccinic anhydride (ODSA) with N,N-dimethylformamide (DMF) or dimethyl sulfoxide (DMSO) as the solvent, at 75°C. The weight gain and acyl content of wool was always higher than that of silk. Tensile properties of silk remained unchanged regardless of weight gain, whereas wool displayed a noticeably higher extensibility at high weight gain. Fine structural changes of acylated wool were detected by DSC analysis. Moisture regain and water retention of acylated silk and wool decreased significantly, whereas water repellency increased. SEM analysis showed the presence of foreign material firmly adherent to the surface of both silk and wool, whose amount increased with increasing weight gain. These deposits were attibuted to the presence of the modifying agents at the fiber surface on the basis of the characteristic IR bands. The possible application of silk and wool fibers acylated with DDSA or ODSA for the preparation of water-repellent textile materials was discussed.