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Yu Wang*, Wiwin Suwinarti*, Shinji Fujiwara*, Kazuhiko Sameshima* and Zhou Cheng**

 * Kochi University (Japan); **Tongji University (Shanghai)

Kenaf bast fiber is composed of primary (P) and secondary (S) phloem fibers. The primary phloem is single layer but the secondary phloem comprised of multiple layers which decreased the number according to the height of the stem section. The higher section, the lower the number of secondary phloem layers. Layer separation was made at the middle part of a stem dan the fiber length, the weight and the viscosity (copper ethylene diamine, CED) were measured. The average fiber length as length weighted fiber length was 2.65-3.00mm (P) and 2.52-2.60mm (S). The primary phloem fiber is obviously longer than the secondary phloem fiber. The weight ratio (P/S) was 0.073. CED viscosity was 76-79cP (P) and 121-124cP (S). The primary phloem had lower viscosity. The five sample paper sheet [A) only secondary phloem, B) no separation, C) and D) increased P/S ratio and E) only primary phloem] pulps were prepared from the lower part of a stem and subjected to paper strength tests. It was shown that with the increase of the primary phloem pulp ratio give inferior strength properties that the only secondary phloem pulp. It could mainly be explained by the lower viscosity of primary phloem. It also means that the production of higher quality kenaf bast paper in strength is not possible by using the higher stem part which has more primary phloem than the lower stem part.

Keywords:  Kenaf, bast fiber, viscosity, fiber length, paper strength and phloem.

(Japan TAPPI Journal, September 2005)