New flax yarn cross-linked with citric acid by thermal treatment or by microwave irradiation

Industrial flax yarn can be successfully cross-linked with citric acid by thermal treatment or by microwave irradiation. Both the methods were applied to an industrial yarn, exactly as it is produced and commercialized. Treatments were run on 100-200 g of yarn spinned on polypropylene cones, i.e. common industrial textile supports. The proposed cross-linking of flax cellulose with citric acid affords a new cross-linked flax yarn, ready to produce new materials of industrial applications, in relationship to the introduced cross-linkage. The new yarn maintains the morphology of the fiber and the textile potentiality of the flax itself and moreover it can be further modified, due to the presence of the citric acid functional group. The bond between cellulose and citric acid is an ester bond, of general interest for polysaccharides. Nevertheless, this bond is critical for the textiles, as it can be broken by high temperature and hydrolyzed in basic media, typical of washing operations. In this context, esterification with polycarboxylic acids like citric acid was found to afford cross-linked cellulose more resistant to heating and basic media.