COMPRESSION WOOD IN Pinus radiata III: KRAFT PULP PROPERTIES

J.E. Diaz-vaz, R. A. Ananias, L. Valenzuela, M. Torres, S. Rodriguez

Abstract


Previous studies with radiata pine trees growing slightly leaned towards one side showed that theyhave small amounts of compression wood with di erent characteristics than the opposite wood atthe other side of the annual rings. ese di erences include shorter tracheids, higher density, higherproportion of lining, higher proportion of extractives in toluene ethanol, and a smaller amount ofalpha-cellulose. e present study compares the properties of kra pulp, with and without bleaching, for mixturesof compression and opposite wood obtained from een 22-year-old radiata pine trees that grewin humid sand soils of Chile. e kra pulp mixture was studied for di erent proportions of 0, 40,70 and 100% compression wood. Considering all mixtures with and without bleaching, the studyreports values between 501 and 695 kg/m3 density, 28 and 51 Nm/g tension index, 18 and 25 mNm2/gtear index, 2,2 and 4,1 kPam2/g burst index, and 44% and 50,6% pulp yield.It was found that the pulp without bleaching from compression wood (for both the internal pulpand the external lumber areas) had lower density, but higher tension, tear, and burst indexes. epulp with bleaching from compression wood had both higher density and tension index, but theother properties only show small random di erences with respect to opposite wood.A higher proportion of compression wood in the mixture reduced pulp yield. e yield for theinternal pulp area was 50,6 % with pure opposite wood and 44% with pure compression wood,while the yield for external lumber area was 48,4% with pure opposite wood and 44,3% with purecompression wood. I was concluded, however, that the relatively small amount of compression woodfound in these trees had only a minor e ect in the properties and yield of kra pulp.

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