The DN 30 hybrid poplar--a fiber source for high strength hardwood pulps.

APPLICATION: This information shows that a hybrid poplar has superior properties to aspen and could lead to a new source of hardwood fiber. Further research is required.

Wood supply is probably the most critical issue governing the long-term competitiveness of the U.S. pulp and paper industry. It was our objective to identify new sources of superior hardwood papermaking fibers from a sustainable source. We started by comparing three hybrid poplars to aspen in order to determine their suitability for chemithermomechanical pulp (CTMP) manufacture. One of clones, designated DN 30 (Populus deltoides P. nigra), appeared to have fiber properties that were more suited for CTMP than aspen fibers. The DN 30 fibers appeared to be more flexible than aspen fibers after sulfonation. After two stages of refining in a 12-in. (30.5 cm) refiner, the average fiber length of the aspen decreased by ~0.20 mm, but only ~0.05 mm for the DN 30. The percent strain (to the point of rupture) in the tensile test was much higher for the DN 30 sheets. The tensile energy absorption was ~40 % higher for DN 30 pulps compared to aspen pulps with the same specific refining energy. The maximum tear index attained was ~6.0 mN*[m.sup.2]/g for aspen and ~8.0 mN*[m.sup.2]/g for DN 30. A hypothesis is presented where the combination of a thin cell wall and large microfibril angle are responsible for the superior properties exhibited by the DN 30 pulp.

Kraft pulps were then produced from DN 30 grown on a different site by another organization. At an equivalent tear index to aspen kraft sheets, the TEA was 75% higher for the DN 30. The higher TEA should result in less breaks on a paper machine. Sheet density and SEM analyses confirmed that the extent of fiber collapse was much greater for the DN 30. Presumably, the DN 30 sheets had a higher relative bonded area, but this alone does not appear to explain the higher percent strain and TEA results. More research is needed to find an explanation and to determine the variation in fiber properties for DN 30 grown on different sites. The two DN 30 investigated had initial average fiber lengths of 0.99 mm and 0.91 mm. View this paper online at http://www.tappi.org/index.asp?pid=28647

Raymond C Francis, Alton F. Brown, and Robert B. Hanna are with Empire State Paper Research Institute. SUNY College of Environmental Science and Forestry, Syracuse, New York 13210, USA; D. Pascal Kamdem is with the Department of Forestry, Michigan State University East Lansing, Michigan 48824 Email Francis at [e-mail].