Variations in paper properties can be due to process conditions but also to variations in wood properties. Better knowledge about the relationships between wood properties and properties of mechanical pulp could lead to a more efficient use of wood resources. AFOCEL has used its thermomechanical pulping (TMP) laboratory pilot refiner to pulp small wood samples and determine the influence wood fibre properties have on pulp fibres. This two-stage laboratory procedure was used within the EU project EuroFiber, which aims at the definition of wood assortments better adapted to the end-product qualities of different European paper mills with TMP plants.
Picea abies (L.) H. Karst. (Norway spruce) trees were sampled in four European countries (Estonia, France, Norway, and Sweden). Samples were taken at different tree heights and split into juvenile, transition, and mature woods, resulting in a total of 450 samples. Wood samples were mechanically pulped after a two-stage refining procedure. Each pulp was characterised by its physical and optical properties, fibre morphology, and specific energy consumption. Data on forest, wood, and pulp properties were compiled and statistically analysed.
Principal Component Analysis revealed a correlation between pulp properties and fibre properties (light-scattering coefficient, fibre length, fines, freeness, brightness, energy consumption).
Five classes of wood were created based on tracheid length and wood density to identify the influence these parameters may have on pulp production (energy consumption, light-scattering coefficient, and tear index).
Finally, a modelling approach enabled us to detect and quantify wood properties and process effects on measured pulp properties. Some categorical data were also tested: wood age (juvenile, transition, and mature wood), country where the tree was grown, and the previous five classes of wood. Part of variances explained by the models was quite low, but showed a general relationship with the specific energy applied during refining and, to a lesser extent, some tendencies with wood properties. With a process that preserved fibre properties well, this work allowed the identification of some wood properties that may be investigated to produce tailor-made pulp.