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 highpressure 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

Cellulose micro and nanofibrils as coating agent for improved printability in office papers

The use of nanocelluloses is being conducted for the most diverse applications. Their performance as coating agent has been mainly explored to improve barrier properties, as they emerge as perfect candidate for plastic substitution, but it is also important to explore their potential to improve printing quality. In the present work, the influence of different nanocelluloses, obtained through mechanical, enzymatic, TEMPO-mediated oxidation and carboxymethylation treatments, in the coating process and inkjet printability of office papers was assessed. The results revealed that the cellulose nanofibrils are better for printability than the microfibrils. But the size and charge of the former must be taken into account, since fibrils of very small size penetrate the paper structure, dragging the pigments from the surface, and very anionic nanofibrils can also have negative influence on the optical density. Besides, an interesting synergy between surface-sizing starch and the cellulose nanofibrils was found to occur as the latter closed the paper structure, which prevented starch from penetrating, while potentiating both of their positive effects on ink pigment entrapment. An additional study of characterization of inkjet pigments was also performed