The fibre, beating, and papermaking properties of kraft pulps prepared from red beech (Nothofagus fusca
(Hook, f.) Oerst.), hard beech (Nothofagus truncata
(Col.) Ckn.), and two silver beech (Nothofagus menziesii
(Hook, f.) Oerst.) wood samples were examined. The anatomical properties and chemical compositions of the wood samples and of fibre and vessel elements in wet pulps and in situ
in handsheets were examined and related to beating effects and papermaking properties. The effects of pulp beating in a Lampen mill, and in a PFI mill at 10 and 25% stock concentrations were evaluated.
Wood chips from the red beech and silver beech samples had similar densities and similar anatomical characteristics. The hard beech chips, on the other hand, were denser by more than 100 kg/m3 and contained proportionately fewer rays and vessels and more fibres than the silver beech and red beech chips. Methanol extractives, ash, lignin, and carbohydrate contents were similar for the silver beech and red beech samples. The high-density hard beech chips contained more methanol extractives and less lignin than the other species.
Pulp yields, fibre and vessel lengths, fibre and vessel diameters, and chemical compositions were in general similar for the red beech and the two silver beech pulps. The hard beech pulp, on the other hand, had the highest yield, the thickest fibre walls, and the longest and widest fibres and vessels.
Effects of beating on beech fibres were in general similar to those on softwood fibres. Ease of pulp beating was dependent on fibre dimensions, particularly fibre wall thickness, and on the conditions and types of beating. Depending on the species and the degree and conditions of pulp beating, wall material was progressively removed from fibre surfaces, fibrillated, and converted into fines. At the same time, fibre walls were progressively disorganised through the development of wall dislocations and delamination, fibres were made flexible and more able to collapse during papermaking, and fibre configurations (kinking) were modified.
Pulp beating at high stock concentrations selectively caused vessels to become fibre-like and ropy. Thus, pulps processed in this way should not be susceptible to vessel picking from paper surfaces during printing. This conclusion was supported by microscopic examination of vessel configurations in paper webs.
Trends for the strength and optical properties of paper prepared from the beech pulps were found to be generally predictable from a knowledge of their characteristics and the types of beating treatments given the pulps. General trends for the different species and the different beating conditions were similar to those obtained with softwood fibres. The exception was paper tearing-strength which increased rather than decreased with pulp beating. The typically low tearing-strengths of hardwood kraft pulps must be related to the shortness and narrow diameters of their fibres when compared with those of softwood fibres.