Synthesis of bio-based polyurethanes from Kraft lignin and castor oil with simultaneous film formation.

Kraft lignin (KL) and castor oil (CO) were used as polyols in the synthesis of bio-based polyurethanes (PUs) in the absence of both solvents and catalysts at room temperature with simultaneous film formation. KL was purified (PKL), and both KL and PKL were fully characterized. CO was mixed with different percentages of PKL (0%, 10%, 30%, and 50%), as well as with polymeric methyl phenyl diisocyanate. After degassing, the reaction mixture was stirred; when the medium viscosity was suitable for spreading, it was poured onto a glass plate, and the thickness was adjusted using an extender. The storage modulus (E', 25 °C) and tensile strength of the lignopolyurethane films (LignoPUCOPKL) were higher than those of the control film (PUCO). LignoPUCOPKL30 and LignoPUCOPKL50 did not break under the conditions that the other films broke under. It was noted phase segregation (rigid and flexible domains) for LignoPUCOPKL30 and LignoPUCOPKL50, and the glass transition temperature (Tg) of the flexible domains (96.2 °C and 52.3 °C, respectively) was higher than that of PUCO (8.4 °C). The formed films were also characterized by scanning electron microscopy, thermogravimetric analysis, X-ray diffraction, contact angles, and swelling tests. To our knowledge, the approach of this study is unprecedented.

Extraction and characterization of nanocellulose structures from raw cotton linter.

This study aimed to characterize nanocellulose extracted from cotton (Gossypium hirsutum) linters. The nanocellulose was subjected to electronic microscopy, thermal analysis, X-ray diffractometry, light scattering, and contact angle. The properties of the nanocellulose are considerably different from the linter. The acidic hydrolyses applied to extract the nanocrystals increased the crystallinity index and the hydrophilicity and decreased the thermal stability. On average, the nanocrystals were 177 nm long and 12 nm wide, with an aspect ratio of 19 when measured by microscopy. The light scattering results were coherent with the crystal dimensions. Cotton linter is a potential source of nanocellulose crystals, particularly to be used in the production of hydrophilic nanocomposites. Extraction of nanocellulose from raw cotton linter does not require pulping.