Toni Antikainen

Analysing density profile characteristics of surface densified solid wood using computational approach

Abstract In this study, solid Scots pine was surface densified in an open press using different moisture contents (9·6 and 12·4%), temperatures (150 and 200°C), press closing times (0·5 and 5 min), holding times (1 and 10 min) and compression ratios (6·7 and 25%). The characteristics of the formed density profiles were defined and their correlations to the process parameters and Brinell hardness and elastic recovery were analysed. Compression ratio and closing time had the strongest effect on the formation of the density profile, as well as the hardness and elastic recovery. The amount of localised deformation (peak area) did not have significant effect on the Brinell hardness or elastic recovery, whereas, the highest density achieved (peak density) and its location (peak distance) dominated the effect. Brinell hardness and elastic recovery were found to correlate well with each other.

Spruce fiber properties after high-temperature thermomechanical pulping (HT-TMP)

Abstract Spruce was submitted to high-temperature (150°C–170°C) refining for 2 or 5 min to produce thermomechanical pulp (TMP) fibers with decreased electrical energy consumption. The pulp was characterized in terms of specific energy consumption as well as tensile and surface properties. The fibers from high-temperature TMP contained more surface lignin even if all sample types usually broke at the S1–S2 cell wall region. They also produced significantly weaker paper sheets, whereas their dry zero-span strength did not suffer substantial losses, indicating decreased fiber-fiber bonding. Tensile strength properties were also determined of a bisphenol-A-epichlorohydrin-based epoxy resin mixed with 5% fiber as a test for fiber-matrix compatibility in composite applications. Based on these preliminary results, high-temperature TMP shows potential for composite reinforcement due to its lower tendency to aggregate and its better compatibility with the tested matrix material.