ABSTRACT
The objective of this study was to produce cellulose acetate (CA) from oat (OH) and soybean (SH) hulls through an eco-friendly solvent-and catalyst-free hydrothermal process, and also to compare the acetylation of cellulose by the conventional synthesis process, employing sulfuric acid as the catalyst, and acetic acid as solvent. Cellulose was extracted from OH and SH using a one-step chlorine-free process, resulting in materials with 86 and 81 % cellulose, respectively. CA samples obtained by hydrothermal process had degrees of substitution ranging from 0.95 to 1.47, and from 1.10 to 1.50, for OH and SH samples, respectively, being classified as monoacetates, while the conventional acetylation resulted in cellulose di- and triacetates. The acetylation by the hydrothermal process did not affect cellulose fibers morphology or crystallinity. CA samples obtained by the conventional process showed changes in their surface morphology, with decrease in crystallinity indexes. Viscosimetric average molar mass increased for all modified samples, with mass gain ranging from 16.26 to 519.70 %. The hydrothermal treatment proved to be a promising process for obtaining cellulose monoacetates with some advantages, including short reaction times, it is a one-step process, and lower effluents generation when compared to the conventional processes.
Subject(s)
Cellulose , Solvents , AcetylationABSTRACT
This paper reports the use of acetylated starch nanoparticles (NPAac) as reinforcement in thermoplastic starch films. NPAac with an average size of approximately 500 nm were obtained by nanoprecipitation. Fourier transform infrared (FTIR) and thermogravimetric analysis (TGA) indicated that NPAac are more thermally stable and essentially amorphous when compared with acetylated starch. Thermoplastic starch films with different proportions of NPAac (0.5, 1.0, 1.5, 10.0%, w/w) were obtained and characterized by scanning electron microscopy (SEM), water vapor permeability (WVP), adsorption isotherms, TGA and mechanical tests. The inclusion of reinforcement caused changes in film properties: WVP was lowered by 41% for film with 1.5% (w/w) of NPAac and moisture adsorption by 33% for film with 10% (w/w) of NPAac; and the Young's modulus and thermal stability were increased by 162% and 15%, respectively, for film with 0.5% (w/w) of NPAac compared to the starch film without the addition of NPAac.