Relation between fibre flexibility and cross-sectional properties

Abstract

The correlation between the fibre flexibility and cross-sectional area moment of inertia of thermomechanical pulp fibres was investigated. The main effects of refining were found to be internal fibrillation, external fibrillation, and fibre shortening. Internal fibrillation increases fibre flexibility and fibre collapsibility, improving fibre-to-fibre contact in a paper sheet. The raw materials used were pulps produced from six different Norway spruce logs and six different Scots pine logs, chosen in a manner that allowed variation of fibre wall thickness and fibril angle independently. Each wood sample was refined in four stages using a pressurized 12″ Sprout Waldron single disc refiner. Fibre flexibility was assessed by FiberMaster bendability measurements. Fibre bendability was measured on the +48 Bauer McNett fractions of the twelve 2nd, 3rd, and 4th stage thermomechanical pulps (TMP). The fibre cross-sectional samples were imaged using scanning electron microscopy (SEM). An image analysis method to calculate the area moment of inertia of each fibre using numerical integration was developed. Fiber bendability increased with specific energy consumption for both wood species (spruce and pine) from the 2nd refining stage to the fourth refining stage. Spruce had a higher rate of bendability increase than pine upon refining. It was expected that fibres with a low area moment of inertia would result in higher bendability, but no such correlation was found for either spruce or pine. Fibre bendability increased with internal fibrillation, as assessed from Simons staining. These results imply that local damage of the fibre wall such as delaminations, kinks, and compressions was the main effect in increasing the flexibility through refining of TMP.

Review: Effects of wood quality and refining process on TMP pulp and paper quality

“…The more the applied energy is consumed for refining pulp, the greater the changes in fiber and pulp properties. Increasing specific energy decreases fibre length (Law 2000), reduces fibre coarseness of long fibre fraction, and fibres become more flexible (Karnis 1994;Rusu et al 2011). Fibres are peeled, collapsed, cell wall thickness decreases (Corson and Ekstam 1994), and cell wall delamination/internal fibrillation increases (Fernando and Daniel 2010;Rusu et al 2011).…”

“…Increasing specific energy decreases fibre length (Law 2000), reduces fibre coarseness of long fibre fraction, and fibres become more flexible (Karnis 1994;Rusu et al 2011). Fibres are peeled, collapsed, cell wall thickness decreases (Corson and Ekstam 1994), and cell wall delamination/internal fibrillation increases (Fernando and Daniel 2010;Rusu et al 2011). On the other hand, the fine content and specific surface area of fines increases with the increase in specific energy (Chagaev and Zou 2007).…”

Modeling the Disc Refining of Lignocellulosic Biomass toward Reduced Biofuel Production Cost and Greenhouse Gas Emissions: Energy Consumption Prediction and Validation

“…Disc refining is an effective but energy-intensive technology that is widely deployed in the pulp and paper industry . Current disc refining technology is optimized to achieve optimal energy consumption with higher strength of the final paper product by increasing fiber flexibility and bonding surface areas . The fines production is minimized to avoid plugging issues in paper production machines.…”

Electrospun Materials with High Reflectance and Polarization Contrast for Sensing Applications in the Mid-Infrared Atmospheric Window

“…We also emphasize that in addition to its excellent optical response in the MIR AW, the D-C mat also maintains mechanical properties appropriate for field deployment, notably by allowing multiple bending-unbending cycles (see Figure S13) and stretching by an additional 50% without apparent deterioration. This capability stems not only from the robustness of POM but also from its processing into fibers, whose form factor has been theoretically shown to allow for more flexibility than the corresponding bulk material …”