Filaments wet-spun from cellulose nanofibril (CNF) hydrogels have strong mechanical performance and chemical versatility, which make them promising for many structural and functional applications. However, they are highly susceptible to the effects of wet or humid conditions, as shown here through studies in dynamic vapor sorption, water absorption and wet tensile testing. The disruptive effects of water could be mitigated by covalently connecting the CNF in the filaments via UV-crosslinkable benzophenone. The applicability of the crosslinked filament in wet conditions was demonstrated by further modifying it into a sensor for hemoglobin. The strong affinity to water was also capitalized on by enhancing the porosity and hydrophilicity of the filament during spinning. This was accomplished in a setup where CNF was enclosed in a supportive polymer shell that enabled coagulation of the filament in water. The resulting filament could absorb more than 40 times its own weight in water and could thus be applied in absorbent products. Likewise, the high affinity to moisture could be utilized in wearable textiles to ensure their breathability. For this purpose, the filament surface was hydrophobized with organosilanes, which led to a water-repellent surface without disturbing the high moisture sorption capacity of the filament. This kind of textiles would be desirable for outdoor use when both breathability and repellence to liquid water are valued.

Water interactions of man-made cellulose I filaments – threat or opportunity?

2019 Spring National Meeting

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