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Palmer, E. R.; Gibbs, J. A. (1973)
Publisher: Tropical Products Institute (TPI)
Languages: English
Types: Book

Classified by OpenAIRE into

mesheuropmc: stomatognathic system, stomatognathic diseases
The pulping characteristics of three trees of Pinus caribaea var hondurensis with different densities grown in Jamaica were determined using the sulphate method. Ten trees, ten years old, had been selected at random from a single plantation in Jamaica and the first, fifth and ninth in order of density were pulped to assess the differences in pulping characteristics that might be due to density. Two digestions, one with 17.5% active alkali, one with 20% were made on each tree using otherwise identical conditions. At both alkali doses yields of pulp increased with increasing density of the wood and, unexpectedly, the Kappa numbers of the pulps from the medium density wood were higher than those of either of the others. The breaking lengths and bursting strengths decreased and the bulk increased with increasing density. When compared at equal digestion conditions, the tearing strengths increased but to a peak with medium density. This was influenced by the higher Kappa numbers of the pulps from medium density wood and, when compared at equal Kappa numbers, the tearing strength showed a marked increase as the wood density increased from low to medium, and a smaller increase as it increased from medium to high density. The same trends held in the case of bleached pulps. Because of the limited scale of this trial and the fact that the medium density sample yielded pulps with Kappa numbers completely out of line with the pulps from the other two samples, it is not possible to draw firm conclusions about the relationship between density and pulping characteristics, or the merit of density for predicting the quality of pulp. However, in this and in earlier similar work (Tropical Products Institute Report L25) it appears that low density trees can have the economic disadvantage of not only higher handling costs but also lower pulp yields per bone dry ton, and the technical disadvantage of giving the lowest tearing strength although with somewhat higher bonding strengths. The choice between medium and highest density is obscure. The conclusion might be different with trees at a different age and site conditions because both these affect the general level of pulp strength and they also affect the relationship between bonding and tearing strength.
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    • 1 TAPPI Standard and Suggested Methods, Published by the Technical Association of the Pulp and Paper Industry, New York.
    • 3 Second Report of the Pulp Evaluation Committee to the (British) Paper Makers' Association, London, 1936.
    • 4 H. W. GIERTZ, Svensk Papperstidning, 1950, 53, 673.
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