Influence of pretreatment and mechanical nanofibrillation energy on properties of nanofibers from Aspen cellulose

The characteristics of cellulose nanofibers (CNFs) depend on many factors such as the raw material, type and intensity of the pre-treatment, and type and severity of the mechanical defibrillation process. The relationship among factors is complex but crucial in determining the final, fit-for-use CNF properties. This study aims to find the relationship between the CNF properties morphology, aspect ratio, nanofibrillation yield, transmittance and cationic demand, and the production process using bleached Aspen thermomechanical pulp as the raw material. Five different types of pretreatments were carried out and five different defibrillation intensities of high-pressure homogenization were evaluated. Pretreatments were: PFI refining at 20,000 revolutions, enzymatic hydrolysis with 80 and 240 g of enzyme per ton of dry pulp and TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl)–mediated oxidation with 5 and 15 mmol of NaClO per gram of dry pulp. From the twenty-five different procedures evaluated, results show that both the pretreatment and the severity of the high-pressure homogenization determined both the fibrillation yield and the CNF morphology. Moreover, the main properties of CNFs (cationic demand, yield, transmittance and aspect ratio) can be estimated from the carboxylic content of the pretreated pulp, which would facilitate the control of the CNF production and their tuning according to the production needs.

Macro, Micro and Nanoscale Bamboo Fiber as a Potential Reinforcement for Composites

Vegetal fibers are obtained from leaves, stalks, culms, fruit and seeds, and have been used in the macro, micro and nanoscale as partial replacement of synthetic fibers in organic and inorganic matrices. Bamboo has high strength fibers, and is one of main nonwood resources and is available in tropical areas worldwide. These characteristics justify the study and application of bamboo fiber as reinforcement in the macro, micro and nanoscale. The macrofibers were obtained from bamboo culms, the microfibers from the chemical pulping and the nanofibers were obtained from the mechanical nanofibrillation of the pulp. The fibers were subjected to chemical, physical, mechanical and morphological tests. There was modification in the chemical composition of the bamboo after pulping, such as decrease of amount of the lignin, hemicellulose and extractives in 42.4%, 33.3% and 83.7%, respectively.The bamboo fibers width have been reduced from 0.26 mm to 19.8 μm after pulping and after nanofibrillation process the width was reduced from 19.8 μm to 16.2 nm.The decrease of the fibers dimension can be seen from the micrographs and analyzing it mechanical properties, the bamboo fibers are a reinforcement potential in macro, micro and nanoscale to organic and inorganic matrices.

Deep eutectic solvent system based on choline chloride-urea as a pre-treatment for nanofibrillation of wood cellulose

Deep eutectic solvent of choline chloride-urea was used as a sustainable pre-treatment media prior mechanical nanofibrillation of wood cellulose.