The preparation and study of cellulose carbamates and their regenerated membranes

Effect of hemicellulose content on the solution properties of cellulose carbamates in NaOH/ZnO aqueous system

Hemicellulose removal from bleached bamboo pulp is key to produce qualified dissolving pulps. In this work, alkali/urea aqueous solution was firstly applied to remove hemicellulose in bleached bamboo pulp (BP). The effect of urea usage, time and temperature on the hemicellulose content of BP was studied. The reduction of hemicellulose content from 15.9 to 5.7 % was achieved in 6 wt% NaOH/1 wt% urea aqueous solution at 40 °C for 30 min. Cellulose carbamates (CCs) were obtained from the esterification of BP with urea. The dissolution behavior of CCs in NaOH/ZnO aqueous solutions with different degree of polymerization (DP), hemicellulose and nitrogen contents were studied by using optical microscope and rheology. The highest solubility was up to 97.7 % when the hemicellulose was 5.7 % and Mη was 6.5 × 104 (g/mol). With the decrease of hemicellulose content from 15.9 % to 8.60 % and 5.70 %, the gel temperature increased from 59.0, 69.0 to 73.4 °C. The apparent gelation time increased from 5640 to 12,120 s with the hemicellulose content increased from 8.60 % to 15.9 %. CC solution with 5.70 % hemicellulose always keeps a liquid-state (G" > G') until the test time reached 17,000 s. The results showed that the removal of hemicellulose, the decrease of DP and the increase of esterification endowed CC with higher solubility and solution stability.

Synthesis, characterization, and biodegradation studies of new cellulose-based polymers

New cellulose carbamates and cellulose acetate carbamates were prepared by classical addition reaction of isocyanates with alcohols. A Telomerization technique was used to make the grafted molecules strongly anchored and more hydrophobic. These molecules were grafted into cellulose and CA chains, respectively. The structures of the synthesized derivatives were confirmed using Nuclear Magnetic Resonance Spectroscopy, Fourier Transform Infrared and Thermogravimetric Analysis, and their solubility phenomenon was also established, and the carbamate derivatives showed better solubility compared to cellulose. Their ability to biodegrade was investigated, and it was concluded that Cell-P₁ and CA-P₁ derivatives are more biodegradable than the other samples. These results suggest that the resulting compounds can be used effectively in many useful industrial fields, for instance, eco-friendly food packaging, domains that use materials that are environmentally friendly and sustainable and the development of green chemistry.

Facile preparation and performance study of antibacterial regenerated cellulose carbamate fiber based on N-halamine

With the outbreak of coronavirus disease (COVID-19) which has incalculable disasters and economic losses, people have given increasing attention to the health and safety of textile and fiber materials. In this study, an eco-friendly, facile, and cost-effective wet-spinning cellulose carbamate fiber technology was developed, and N-halamine regenerated cellulose fiber (RCC-Cl) with rechargeable and rapid bactericidal properties were prepared by the Lewis acid-assisted chlorination method. The chemical properties of the fibers were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric analysis, and energy-dispersive X-ray spectroscopy. The mechanical and surface topography of the treated fiber was investigated by tensile testing and scanning electron microscopy. The results showed that the mechanical properties of RCC-Cl fibers can reach a breaking strength of 12.1 cN/tex and a breaking elongation of 41.4% with the optimized spinning process. Furthermore, RCC-Cl showed excellent antimicrobial activities, which can inactivate Escherichia coli and Staphylococcus aureus at a concentration of 10⁷ CFU/mL within 1 min. This work provided a novel approach to produce regenerated cellulose fibers with antibacterial properties, showing great potential in the field of functional textiles.

Dissolution and Interaction of Cellulose Carbamate in NaOH/ZnO Aqueous Solutions

The dissolution and molecular interactions of cellulose carbamate (CC) in NaOH/ZnO aqueous solutions were studied using optical microscopy, differential scanning calorimetry (DSC), ¹H NMR, dynamic light scattering (DLS), atomic force microscopy (AFM), transmission electron microscopy (TEM), and molecular dynamic simulation. The dissolution of CC in NaOH/ZnO aqueous solutions using the freezing–thawing method was an exothermic process, and the lower temperature was favorable for the dissolution of CC. ZnO dissolved in NaOH aqueous solutions with the formation of Zn(OH)₄²⁻, and no free Zn²⁺ ions existed in the solvents. NaOH/Na₂Zn(OH)₄ system formed strong interactions with the hydroxyl groups of CC to improve its solubility and the stability of CC solution. The results indicate that 7 wt% NaOH/1.6 wt% ZnO aqueous solution was the most appropriate solvent for the dissolution of CC. This work revealed the dissolution interaction of CC-NaOH/ZnO solutions, which is beneficial for the industrialization of the CarbaCell process.

New insensitive high-energy dense biopolymers from giant reed cellulosic fibers: their synthesis, characterization, and non-isothermal decomposition kinetics

Renewable giant reed has been explored for the first time to develop new advanced high-energy dense biopolymers through carbamate surface functionalization and nitration of native cellulose and cellulose microcrystals.