No abstract

The temperature-composition phase diagram in the diluted region of the cationic surfactant cetyldimethylbenzylammonium salicylate/water system was studied with a battery of techniques. The Krafft temperature (T k = 33 ± 1°C) was measured by differential scanning calorimetry, polarizing microscopy, conductimetry, viscosimetry, and rheometry. The critical vesicle concentration (cvc, *0.002 wt%) and a vesicle-micellar transition (cvm, *0.005 wt%) was detected at a temperature of 35°C. Below T k and concentrations B2 wt%, a transparent solution is formed (I). Above 2-8.5 wt%, a lamellar (L 1 ) phase forms. At higher concentrations and up to 12 wt%, a second lamellar phase (L 2 ) is detected. From 12.4 to 15.5 wt%, an emulsion phase (E) is formed. Rheological dynamic measurements for the I phase indicate that the system exhibits a predominantly viscous behavior (G 0 \ G 00 ) for concentrations lower than the overlap or entanglement concentration (C e , *0.75 wt%). At higher concentrations, wormlike micelles form and the elastic behavior predominates (G 0 [ G 00 ). The elastic (G 0 ) modulus collapses in a concentration-time master curve in the whole reduced frequencies range xs c examined, whereas the viscous modulus (G 00 ) collapses only at reduced frequencies lower than 0.1. Reduced stress plotted as a function of the reduced shear rate yields a good superposition of the curves at the different concentrations up to the onset of the non-linear behavior.

Natural lignocellulosic biomass is a valuable feedstock for soluble-grade cellulose (α-cellulose > 90%) with advantageous features such as abundance, high strength, rigid structure, low weight, and it is biodegradable. The bagasse from Agave tequilana Weber var. azul is the main agroindustrial waste from the tequila industry and poses an environmental threat. However, due to its high cellulose content, Agave tequilana bagasse is an excellent candidate for the extraction and utilization of its components. In this study, alkaline cooking, followed by five stages of bleaching, was employed to obtain soluble-grade cellulose pulp. The obtained soda pulp material had a Kappa number (KN) of 23 ± 3, viscosity (μ) of 11.53 to 10.18 cp, degree of polymerization (DP) of 830 to 750, brightness of 87.5%, and percentage of alpha-cellulose (α) of 81 ± 3 at 94 ± 3%. The obtained material was characterized using X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy to compare its properties with published information. The waste of A. tequilana Weber var. azul produced pulp with a high percentage of alpha cellulose and a high crystallinity degree. This methodology is novel and simple for the production of soluble-grade cellulose pulp, a raw material for the production of cellulose nanocrystals.