Abstract
Colloidal dispersions of cellulose nanofibrils (CNFs) are viable alternatives to cellulose II dissolutions used for filament spinning. The porosity and water vapor affinity of CNF filaments make them suitable for controlled breathability. However, many textile applications also require water repellence. Here, we investigated the effects of postmodification of wet-spun CNF filaments via chemical vapor deposition (CVD). Two organosilanes with different numbers of methyl substituents were considered. Various surface structures were achieved, either as continuous, homogeneous coating layers or as three-dimensional, hairy-like assemblies. Such surface features reduced the surface energy, which significantly affected the interactions with water. Filaments with water contact angles of up to 116° were obtained, and surface energy measurements indicated the possibility of developing amphiphobicity. Dynamic vapor sorption and full immersion experiments were carried out to inquire about the interactions with water, whether in the liquid or gas forms. Mechanical tests revealed that the wet strength of the modified filaments were almost 3 times higher than that of the unmodified precursors. The hydrolytic and mechanical stabilities of the adsorbed layers were also revealed. Overall, our results shed light on the transformation of aqueous dispersions of CNFs into filaments that are suited for controlled interactions with water via concurrent hydrolysis and condensation reactions in CVD, while maintaining the moisture buffering capacity and breathability of related structures.
Highlights
The scarcity of fossil resources, climate change, and sustainability are some of the current megatrends that have triggered a renewed interest in biobased materials
Alternative methods have been introduced for obtaining textile filaments from cellulose nanofibrils (CNFs) through spinning.[4−17] Compared to filaments from native and regenerated cellulose, those from CNFs have the potential to develop advanced moisture sorption profiles, given their high surface area and colloidal size, which can be exploited to obtain an optimal porosity, depending on the spinning conditions
The organosilane gas−solid reaction via chemical vapor deposition (CVD) was effective for surface modification of the filaments by condensation reactions, as has been reported between cellulose surface hydroxyl groups and Si−Cl moieties.[21]
Summary
The scarcity of fossil resources, climate change, and sustainability are some of the current megatrends that have triggered a renewed interest in biobased materials. Higher hydrophobicity and lower moisture sorption, were the ones that underwent the highest reduction in strength This can be explained by the fact that their surface coverage was not homogeneous (as assessed by SEM); i.e., they were subjected to more extensive interaction with water via the more accessible and unprotected hydroxyl groups at the surface of the filaments. When exposed to liquid water for a prolonged time, the TC-modified filaments, which generally presented higher hydrophobicity and lower moisture sorption, were the ones that underwent the highest reduction in strength The results show promise in the utilization of naturally based filaments, for example, in wearable materials, given their hydrophobic but breathable character
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