Chemically-bonded nonwoven is commonly used in single-use products, and are often composed of cellulose fibers with a fossil-based binder. To reduce the amount of plastic littering, we investigated a biobased and biodegradable binder consisting of polyelectrolyte complexes based on chitosan, carboxymethyl cellulose and citric acid. The binder significantly improved the mechanical properties of two different types of cellulosic fiber systems in both dry and wet states. The quality of the water used in the binder had a significant impact on the mechanical properties, especially in the dry state, indicating a beneficial effect by the presence of cations. It was shown that covalent bonds were formed during the low temperature drying, and that the amount of bonds increased with a high temperature curing. Electron microscopy and tensile data indicated that the binder acted as a joint between the fiber/fiber parts. The presented results enable a sustainable solution for the current plastic-based nonwoven industry.

Using biobased polyelectrolytes to emulsify natural fatty molecules is one possible key technology to create sustainable materials. The emulsions can be used in papermaking instead of synthetic hydrophobizing agents or in nonwoven manufacturing to create strong, hydrophobic textile-like materials. This article investigates a novel emulsification system based on a polyelectrolyte complex between chitosan dissolved in citric acid and carboxymethyl cellulose together with sunflower (Helianthus annuus) oil. Viscose nonwoven treated with the emulsion had a contact angle of over 120°. Tensile tests showed that the produced paper and nonwoven materials achieved high dry and, especially, high wet strength. Infrared spectroscopy illuminated the impact of heat curing the binder, and electron microscopy showed that the oil droplets from the emulsion were spread across the fibre surface. The results from this study enable sustainable nonwovens to be applied in areas where high dry and wet strength and water repellence are required; this includes outdoor applications, including agricultural mulch films, where nonwoven is used frequently and a sustainable approach is urgently needed to reduce the accumulation of plastics in the environment.

Chemically bonded nonwovens are strong, paper-like materials that traditionally contains a latex binder comprising a plastic polymer and (often) cellulosic fibers. With this composition, these materials are only partly biobased, having a low biodegradability and cannot be recycled in traditional waste streams. In the strive for a fully biobased nonwoven system with a hydrophobic character, a biobased binder (polyelectrolyte complex, PEC) out of carboxymethyl cellulose and chitosan dissolved in citric acid) was here combined with pea protein (PP). By varying the fat content in the pea protein, as well as the content of the protein in the binder, it was possible to obtain different degrees of cellulosic nonwoven hydrophobicity and mechanical properties. At equal amounts of PEC and PP, the cured system showed a contact angle of & AP;120 degrees, which was stable in time. As compared to the binder-free nonwoven, the dry strength was doubled in the presence of defatted PP, and the stiffness and strength in the wet state was significantly higher for all combinations between PEC and PP.

The amount of disposable nonwovens used today for different purposes have an impact on the plastic waste streams which is built up from several single-use products. A particular problem comes from nonwoven products with “hidden” plastic (such as cellulose mixed with synthetic fibers and/or plastic binders) where the consumers cannot see or expect plastic. We have here developed a sustainable binder based on natural components; wheat gluten (WG) and a polyelectrolyte complex (PEC) made from chitosan, carboxymethyl cellulose and citric acid which can be used with cellulosic fibers, creating a fully biobased nonwoven product. The binder formed a stable dispersion that improved the mechanical properties of a model nonwoven. With WG added, both the dry and the wet strength of the impregnated nonwoven increased. In dry-state, PEC increased the tensile index with >30 % (from 22.5 to 30 Nm/g), and with WG, with 60 % (to 36 Nm/g). The corresponding increase in the wet strength was 250 % (from 8 to 28 Nm/g) and 300 % (to 32 Nm/g). The increased strength was explained as an enrichment of covalent bonds (ester and amide bonds) established during curing at 170 °C, confirmed by DNP NMR and infrared spectroscopy.