Green and efficient method for preparing all-cellulose composites with NaOH/urea solvent

All-cellulose composite (ACC) was made from sulphite dissolving pulp fibres by using a partial dissolution method with sodium hydroxide/urea (NaOH/urea) solvent at a low temperature. The resultant composites were compared with untreated sheets. The effect of dissolution time (2, 30, 60, 120 and 240 s) were monitored by XRD, FESEM and mechanical tests. The initial fibre structure was transformed into a thoroughly consolidated composite material after a 30 s dissolution time, and the tensile strength was 14 times higher than that of the untreated fibre sheet without affecting strain. At the same time the amount of non-crystalline matrix in the ACC increased, and the apparent crystallinity decreased. Dissolution times of longer than 30 s had no or a minor effect on crystallinity and mechanical properties.