Perfect balance between the water absorption and mechanical properties of carboxymethyl cellulose/polyvinyl alcohol electrospun nanofibre pads through citric acid cross-linking

Natural polysaccharides combined with biodegradable polymers are used as raw materials to obtain nanostructures through electrospinning, and they have attracted attention in many fields (such as food packaging pads) because of their high water absorption. However, maintaining physical stability while absorbing water in this cross-linked porous structure is challenging. In this study, a modified nanofibre absorbent membrane was prepared by electrospinning using carboxymethyl cellulose (CMC) and polyvinyl alcohol (PVA) (2:8, w/w) as the matrix materials and citric acid (CA, 0%, 5%, 10%, and 15%, w/w relative to the total weight of the CMC and PVA polymers) as the cross-linking agent. Under 10% CA, the fibre membranes achieved a 1597% water absorption rate with only 15% solubility, and they exhibited satisfactory tensile strength (TS) and elongation at break (EB). Experimental results have shown that the high water absorption rate of nanofilms is attributed to an improvement in nanostructure uniformity. In this study, the mechanical stability of the nanofilm after water absorption was due to the crosslinking effect of macromolecules caused by CA. FT-IR and XPS results showed that CA and the matrix material might have undergone esterification cross-linking reactions, which consumed the hydroxyl groups in the material and increased the ester group content. XRD showed that CA changed the crystal structure of the material. The incorporation of 15% CA resulted in enhanced thermal stability, solubility, and surface wettability but a reduction in water absorption, TS, and EB of the nanofibres. In general, an appropriate amount of CA can be used to balance the mechanical properties and water absorption characteristics of an electrospinning nanofibre pad. A nanofibre absorbent pad with 10% CA (NFs/CA 10%) demonstrated suitable surface wettability, strong tensile strength, and strong water absorption, and it could maintain integrity in water, indicating that it has potential application value and good application prospects in the field of food absorbent pads.