EFFECTS OF REFINING TEMPERATURE AND PRESSURE ON CHEMICAL AND PHYSICAL STRUCTURE OF LOW-ENERGY THERMOMECHANICAL PULP (ASPLUND FIBERS) DETERMINED BY RAPID FTIR ANALYSIS

Asplund fibers are manufactured using low-energy thermomechanical pulping. They have traditionally been used in fiberboard applications. Since Asplund fibers have a high specific surface area (SSA), they can find new uses as biorefinery feedstock. However, little is known about how the Asplund process parameters affect the chemical and physical structure of the fibers. This research examined the effect of refining temperature and pressure on softwood fiber properties at refining temperatures ranging from 170 °C to 200 °C. Spruce chips were subjected to a pilot-scale Asplund refining process. FTIR analyses revealed ordering of cellulose macromolecules at elevated temperatures up to 190 °C. Ordering of cellulose was confirmed by XRD analyses. FTIR analyses also suggested lignin condensation at elevated temperatures. SEM images showed improved fiber separation at higher temperatures when compared to the temperatures of 170 °C and 180 °C. These findings are useful when developing novel biorefinery concepts, where Asplund fibers are used as feedstock.