Abstract
In this study, cellulose microfibers and cellulose nanofibers (CNF) prepared from recycled boxboard pulp using a mechanical fine friction grinder were used as reinforcements in a board sheet. Micro- and nanofibers manufactured by mechanical grinding have typically broad particle size distribution, and they can contain both micro- and nano-sized fibrils. Deep eutectic solvent of choline chloride and urea was used as a non-hydrolytic pretreatment medium for the CNF, and reference CNF were used without any chemical pretreatment. The CNF were ground using three grinding levels (grinding time) and their dosage in the board varied from 2 to 6 wt%. The results indicate that the board properties could be tailored to obtain a balance between the processability and quality of the products by adjusting the amount of CNF that was added (2–6 wt%). A preliminary cost assessment indicated that the most economical way to enhance the board strength properties was to add around 4% of CNF with a moderate grinding level (i.e., grinding energy of 3–4 kWh/kg). Overall, the strength properties of the manufactured board sheets improved by several dozen percentages when CNF was used as the reinforcement.
Highlights
The production of nano-scale cellulose fibers and their application as reinforcements in materials have gained increasing attention due to the high strength and stiffness of the nanocelluloses combined with their small size, high surface area and aspect ratio, low weight, biodegradability, and renewability (Siroand Plackett 2010; Hassan et al 2011; Suopajarvi et al 2017)
Cellulose nanofibrils or nanofibers (CNF) produced by mechanical disintegration of cellulose without any chemical treatments are one of the simplest types of nanomaterials based on renewable resources
The optical resolution of FS5 ultra-high definition (UHD) camera unit is close to 1 lm, which means that the smallest particles are not visible in practice and not included in the calculations
Summary
The production of nano-scale cellulose fibers (nanocelluloses) and their application as reinforcements in materials have gained increasing attention due to the high strength and stiffness of the nanocelluloses combined with their small size, high surface area and aspect ratio, low weight, biodegradability, and renewability (Siroand Plackett 2010; Hassan et al 2011; Suopajarvi et al 2017). The mechanical fibrillation process causes permanent changes in the cellulose fiber structure, and it increases the bonding ability of cellulose by modifying the morphology and reducing the size of the fibers (Kamel 2007; da Costa Correia et al 2016). High tensile strength and tensile stiffness contribute to the stacking strength of corrugated paperboard by reducing the risk of box wall bulging; they are desired properties of board applications
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