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DENSITY, ANATOMY, PULP AND HAND-SHEET PROPERTIES OF
INNER-WOOD AND OUTER-WOOD OF PINUS PATULA

Authors

Anton Zbonak and James Wesley-Smith

Company

CSIR

Keywords

Pinus patula, inner-wood, outer-wood, anatomy, density, fibre length, microfibril angle, pulp, handsheet strength

 

 

 

 

ABSTRACT

The present work compared the properties of wood sampled from inner- (juvenile) and outer- (mature) areas of Pinus patula trees grown in different site qualities, as well as the characteristics of pulp and hand-sheets manufactured from these segments.

Ten trees aged 14 were sampled from each of three site qualities. Anatomy, density, fibre length and microfibril angle (MFA) were measured in discs extracted at breast-height from all trees. Preliminary studies revealed that an abrupt change in MFA occurred at about 8 years of age, and this criterion was used to separate inner and outer regions of each disc. Wood from the same region for each site quality was chipped and bulked into a total of six samples. Samples were pulped by the Kraft method, beaten and hand-sheets made. Anatomical and density data, in combination with tensile, tear and burst strengths, and brightness, porosity and bulk values measured in hand-sheets, were contrasted between wood from inner and outer regions.

Results show that inner-wood of P. patula trees is characterised by shorter tracheids having with small diameter. Cell walls of inner wood fibres were thinner, which reflected in lower wood density. The MFA of inner-wood was significantly higher than that from outer-wood. Pulp from inner-wood had relatively lower yield and higher consumption of chemicals compared to outer-wood. Hand-sheets made from outer-wood segments showed higher tear index, zero-span tensile index but lower porosity and sheet density. Burst index, tensile index and optical properties of handsheet were not affected by position in disc.

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