Strength and Water Interactions of Cellulose I Filaments Wet-Spun from Cellulose Nanofibril Hydrogels.

Hydrogels comprising cellulose nanofibrils (CNF) were used in the synthesis of continuous filaments via wet-spinning. Hydrogel viscosity and spinnability, as well as orientation and strength of the spun filaments, were found to be strongly affected by the osmotic pressure as determined by CNF surface charge and solid fraction in the spinning dope. The tensile strength, Young's modulus and degree of orientation (wide-angle X-ray scattering, WAXS) of filaments produced without drawing were 297 MPa, 21 GPa and 83%, respectively, which are remarkable values. A thorough investigation of the interactions with water using dynamic vapour sorption (DVS) experiments revealed the role of sorption sites in the stability of the filaments in wet conditions. DVS analysis during cycles of relative humidity (RH) between 0 and 95% revealed major differences in water uptake by the filaments spun from hydrogels of different charge density (CNF and TEMPO-oxidised CNF). It is concluded that the mechanical performance of filaments in the presence of water deteriorates drastically by the same factors that facilitate fibril alignment and, consequently, enhance dry strength. For the most oriented filaments, the maximum water vapour sorption at 95% RH was 39% based on dry weight.

Acid-generated soy protein hydrolysates and their interfacial behavior on model surfaces.

The present work attempts to provide data to warrant the consideration of soy proteins (SP) as potentially useful biomolecules for practical chemical and surface applications. Despite their sundry properties, SP use has been limited by their high molecular weight. In response to this limitation, we analyze acid hydrolysates of soy proteins (0.1 N HCl, 70 °C) for surface modification. Techniques typical in protein (SDS-PAGE) as well as colloidal (charge demand and electrophoretic mobility) analyses were used to follow the effects of molecular changes that occur upon hydrolysis. Adsorption experiments on hydrophobic (polypropylene) and mineral (aluminum oxide) surfaces were subsequently carried out to further interrogate the surface activity resultant from soy hydrolysis. It was found that during adsorption the hydrolysates tended to form less surface aggregates and adsorbed at faster rates compared with unmodified SP. Overall, the benefits derived from the application of SP hydrolysates are highlighted.