Comprehensive Study on Cellulose Swelling for Completely Recyclable Nonaqueous Reactive Dyeing

The swelling of cotton by non-nucleophilic organic solvents was investigated to achieve completely recyclable reactive dyeing. The degree of swelling was determined and correlated to the Hansen Solubility Parameter distance (<i>Ra</i>) of cellulose to the solvents and the dielectric constant of the solvents (ε). The effect of swelling temperature was also investigated. Preswelling of cotton fabrics by 150 °C <i>N</i>,<i>N</i>-dimethylacetamide (DMAc) for 1 h was found to be sufficient to accelerate dye sorption. Dyeing was carried out using C.I. Reactive Red 24 in a 40/60 mixture of DMAc and dimethylcarbonate (DMC), a cosolvent selected to facilitate dye exhaustion. The efficiency of unfixed dye removal was found to predominantly correlate to swelling (<i>R</i>² = 0.9236). Excellent colorfastness was achieved with 4 rinses by 95 °C DMAc. A 10-cycle repeated dyeing sequence was demonstrated to give 43% and 90% reduction in dye consumption and disposal. The overall reduction in material disposal was estimated to be over 99.99%. The favorable results indicated that discharge-free reactive dyeing could be made possible

Electrothermal Phase Change Composite with Flexibility over a Wide Temperature Range for Wearable Thermotherapy

Flexible electrothermal composite phase change materials (PCMs) are promising candidates for portable thermotherapy. However, a great challenge remains to achieve high PCM loading while maintaining reasonable flexibility. Herein, the polypyrrole-decorated melamine foam (PPy@MF) was fabricated and thereafter applied to confine binary PCM mixtures composed of a high-enthalpy long-chain polyethylene glycol (PEG4000) and its short-chain homologue (PEG200) to make the novel PPy@MF-PEG4000+200 composite PCM. At a high loading of up to 74.1% PEG4000 and a high latent heat energy storage density of 150.1 J/g, the composite PCM remained flexible at temperature (−20 °C) far below its phase transition point thanks to the plasticine effect of PEG200. The composite also demonstrated good Joule heating performance, providing fast heating from 28 to 70 °C at low applied voltages (4.5–6.0 V). The energy could be stored efficiently and released to maintain the composites at the proper temperature. The electrothermal performance of the composite remained undisturbed during curved or repeated bending, showing good potential to be used for personal thermal management and thermotherapy

Green Finishing of Cotton Fabrics Using a Xylitol-Extended Citric Acid Cross-linking System on a Pilot Scale

Cross-linking is frequently applied to cotton fabrics for enhanced wrinkle recovery and dimensional stability. The combination of citric acid (CA) and xylitol shows great potential as a sustainable alternative to the market-dominating <i>N</i>-methylol resins, which are inherently formaldehyde-releasing. This paper reports a successful pilot-scale application of this green cross-linking system preceded by systematic investigation using response surface methodology (RSM). Responses of fabric properties to five foremost variables were investigated to gain insight of the cross-linking system and facilitate its industrialization. The model obtained by RSM suggests that curing temperature is the most prominent variable and the responses to CA and xylitol concentrations are closely coupled. The optimum conditions used for the pilot-scale experiments were 3 min, 175 °C, 130 g/L, 15 g/L, and 3 kg/cm² for curing time, curing temperature, CA concentration, xylitol concentration, and padder-roll pressure, respectively. The CA/xylitol finished fabrics were comparable to those finished with the market-dominating dimethylol­dihydroxy­ethylene­urea (DMDHEU) resins. Analyses show that CA/xylitol is more cost-effective than other formaldehyde-free cross-linking agents and clearly has a more preferable environmental, health, and safety (EHS) profile than DMDHEU. The encouraging results indicate that CA/xylitol has great potential in replacing <i>N</i>-methylol resins on an industrial scale

Fabrication of Thermoresponsive Polymer-Functionalized Cellulose Sponges: Flexible Porous Materials for Stimuli-Responsive Catalytic Systems

In this present work, a thermoresponsive and recyclable catalytic system was prepared by grafting poly­(<i>N</i>-isopropylacrylamide)-<i>co</i>-poly­(glycidyl methacrylate) (PNIPAM-<i>co</i>-PGM) to a cellulose sponge, which was reinforced by polydopamine (PDA) and (3-aminopropyl)­triethoxysilane (APTMS). Au nanoparticles (Au NPs) were loaded via in situ reduction of HAuCl₄ with PDA. Fourier transform infrared, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis results revealed that the Au NPs (<10 nm) were homogenously dispersed on the surface of the sponge. Catalytic experiments with sponges prepared without PNIPAM-<i>co</i>-PGM demonstrated an increased reaction rate when the temperature of the reaction medium was elevated. However, in the presence of PNIPAM-i<i>co</i>-PGM in the sponges, the reaction rate was decreased when the reaction temperature was higher than the lower critical solution temperature of the polymer. The sponge could be conveniently separated from the reactions and reused up to 22 cycles

Enamine Approach for Versatile and Reversible Functionalization on Cellulose Related Porous Sponges

A readily modifiable cellulose sponge was prepared from cellulose acetoacetate (CAA). Facile postsynthetic modification with primary amino-containing modifiers such as octadecyl amine (ODA), cysteine (CYS), and l-glutamic acid (GLU) could be achieved demonstrating the ease of anchoring a broad selection of functional groups to the surface of the sponges. This postsynthetic modification process was systematically characterized by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, which confirmed the formation of the enamine bonds. Besides, the microstructures and mechanical properties of the sponges were well preserved throughout the postsynthetic modification process. The enamine bonds, as one of the dynamic covalent bonds, were easily formed under mild and neutral conditions and broken under exposure to a low pH stimulus. The enamine bonds were used to modify the CAA sponges, which can achieve the versatility and recycling of cellulose porous materials. Therefore, the resulting sponges could serve as a versatile precursor to a broad spectrum of multifunctional porous materials, paving a new way for constructing smart sponges through the postsynthetic modification strategy