Proceedings of the 51st International Convention of Society of Wood Science and Technology November 10-12, 2008 Concepción, CHILE Technological characterization of Chusquea culeou, a bamboo growing in Chile H. POBLETE, R. JUACIDA, H. CUEVAS, J.E. DIAZ-VAZ Inst. Tecnología de Productos Forestales Universidad Austral de Chile Email: [email protected] SUMMARY A technological characterization of Chusquea culeou Desv. (colihue), a bamboo growing in Chile, was conducted. Physical, chemical and mechanical properties, considering plant diameter, position in culm length and nodal or internodal sections, were determined. Keywords: Chusquea culeou, bamboo, mechanical, chemical properties. Paper WS-41 1 of 8 Proceedings of the 51st International Convention of Society of Wood Science and Technology November 10-12, 2008 Concepción, CHILE INTRODUCTION Colihue (Chusquea culeou Desv.) is one of eleven bamboo species of the Chusquea genus growing in Chile. The estimated surface where colihue is present reaches 180.000 ha with a productivity of 10 tons/ha/year or 12 m³/ha/year. Colihue has no industrial utilization in Chile (Campos et al 2003). The technological characterisation of colihue wood was the aim of this study. The determinations were oriented to obtain information about physical and mechanical properties, anatomical structure, fibre length and chemical composition. MATERIALS AND METHODS. Colihue culms were collected selecting those showing a straight form and no insect attack. A diameter classification was done (thick > 3 cm and thin < 3 cm). Five centimetre long test pieces from the top, middle and base of 200 culms of each diameter class were analysed. Test pieces included nodal and intermodal sections. Physical and anatomical determinations. Moisture content, specific weight, fibre length and some anatomical observations were conducted. The determinations considered position in the culm length, nodes or internodes, and two culm diameter classes, bigger and less than 3 cm. Chemical composition. Extractives in cold and boiling water, 1% NaOH, ethanol and ethanol toluene according to TAPPI T 204-om-88 were determined. Determinations of holocellulose (Poljak), cellulose (Kurschner and Hoffer) and lignin (TAPPI T 222 om-88) were also conducted. Mechanical properties. Shear strength (ASTM D-5751), MOR and MOE (DIN 52 186), compression (parallel to fibres – DIN 52 185), and hardness (Janka) were tested. Figure 1. Shear test pieces. A: without node, B: node at the centre. Paper WS-41 2 of 8 Proceedings of the 51st International Convention of Society of Wood Science and Technology November 10-12, 2008 Concepción, CHILE ANATOMICAL ASPECTS, PHYSICAL PROPERTIES. Culms are formed by about 50% of parenchyma cells, 40% corresponding to fibres and 10% to vessels and sieve tubes. The proportion of cell types varies within a single culm and across its length and width. a. Node section b. Inter nodal section Figure 2. Transversal sections of colihue. In nodes and internodes, vascular bundles with one phloem field and two metaxylem vessels (labelled as V) are always present. The vascular bundles are surrounded by fibres and inserted in parenchyma tissue. The phloem field looks like a cluster arranged and located within the two vessels. The parenchyma tissue surrounding vessels and phloem has thin cell walls and round section. This tissue contain relatively small intercellular spaces, some times not visible. The most important difference between nodes and internodes is the fibre wall thickness. Fibres in nodes sections have thicker cell walls. In the nodal sections the high amount of fibres in every vascular bundle and the higher amount of vascular bundles, are probably responsible for the higher specific weight of this part of the culms. Fibre length. The position in the culm height had no significant effect on the length of fibres. Culm diameter seems to have some effect on fibre length (Figure 3). Specific weight. In figure 4 specific weight results are presented. The internodal sections had lower values than nodal material. The specific weight of culms with diameters bigger than 3 cm was lower than the measured in thin culms in the intermodal sections. The nodal sections of the two diameter classes showed no significant differences in their specific weight. When the height position in culm was considered, an increment of Paper WS-41 3 of 8 Proceedings of the 51st International Convention of Society of Wood Science and Technology November 10-12, 2008 Concepción, CHILE specific weight from base to top was detected. Moisture content. The moisture content was always higher in the intermodal than in the nodal sections (Figure 5). Culms with diameter bigger than 3 cm showed higher moisture contents. Both diameter classes showed an slight trend to decrease moisture content from the base to the top of the culm 2,0 1,8 1,6 1,4 1,2 1,0 0,8 0,6 FIBRE LENGTH (mm) FIBRE 0,4 0,2 0,0 NODE INTERNODE NODE INTERNODE NODE INTERNODE POSITION: BASE POSITION: MIDDLE POSITION: TOP CULMS < 3 cm CULMS > 3 cm Figure 3. Fibre length of colihue in two diameter classes (<3cm, >3cm), three positions in culm length and in nodes or internodes sections. Paper WS-41 4 of 8 Proceedings of the 51st International Convention of Society of Wood Science and Technology November 10-12, 2008 Concepción, CHILE 0,8 0,75 ) 0,7 0,65 0,6 0,55 SPECIFIC WEIGHT (g/cm³ 0,5 0,45 0,4 NODE INTERNODE NODE INTERNODE NODE INTERNODE POSITION: BASE POSITION: MIDDLE POSITION:TOP CULMS< 3 cm CULMS> 3 cm Figure 4: Specific weight of colihue. Two diameter classes (<3cm, >3cm), three positions in culm length and in nodes or internodes sections. 160 140 120 100 80 MOISTURE CONTENT (%) - (%) CONTENT MOISTURE 60 40 NODAL INTERNODAL NODAL INTERNODAL NODAL INTERNODAL POSITION: BASE POSITION: MIDDLE POSITION: TOP CULMS < 3 cm CULMS > 3 cm Figure 5. Moisture content of colihue, considering two diameter classes (<3cm, >3cm), three positions in culm length and nodes or internodes sections. Paper WS-41 5 of 8 Proceedings of the 51st International Convention of Society of Wood Science and Technology November 10-12, 2008 Concepción, CHILE CHEMICAL COMPOSITION The intermodal material had a higher amount of extractives. The high content of extractable compounds, mostly acidic in nature, is reflected in the pH value. The ash content from this bamboo is almost four times higher than the reported for wood species growing in Chile. Table 1: Chemical composition of nodal and intermodal sections of colihue NODAL INTERNODAL Extractives: (%) (%) Cold water 12,6 13,1 Boiling water 13,2 14,3 NaOH (1%) 32,0 33,5 Ethanol 15,5 16,1 Ethanol-toluene 14,6 14,9 Total extractable compounds 16,8 17,8 Holocellulose 73,1 71,9 Cellulose 51,4 51,5 Lignin 22,3 23,0 Ashes 1,2 1,3 pH – cold water extractive 3,5 3,7 pH – boiling water extractive 4,5 4,6 MECHANICAL PROPERTIES Shear strength. No significant differences between nodes and internodes were determined. The obtained shear strength is higher than values reported by Perez (1983) for Populus sp. and similar to the values obtained with Pinus radiata, 61 and 100 kg/cm² respectively. Table 2: Shear strength NODAL INTERNODAL Parameter (kg/cm2) (kg/cm2) Average 92,27 92,66 Standard Desv. 17,49 17,73 Variation Coefficient 18,96 19,13 Minimum 57,42 64,59 Maximum 138,95 135,17 Paper WS-41 6 of 8 Proceedings of the 51st International Convention of Society of Wood Science and Technology November 10-12, 2008 Concepción, CHILE Bending strength (MOR and MOE). The presence of nodes in the middle of the test pieces, produced a lower modulus of rupture. The tension at the proportional limit is positively affected by the presence of nodes. According to MOE results, test pieces with nodes were more rigid than those prepared only with internodal material. Table 3: Bending strength, MOR and MOE. NODAL INTERNODAL Fibre stress at Fibre stress at Parameter proportional MOR MOE proportional MOR MOE 2 2 2 2 limit (σPL) (kg/cm ) (kg/cm ) limit (σPL) (kg/cm ) (kg/cm ) (kg/cm2) (kg/cm2) Average 356,25 610,73 74.703,13 313,75 631,25 67.687,50 Standard Desv. 101,30 156,52 20.124,17 103,95 165,44 17.253,21 Variation Coef. 28,43 25,63 26,94 174,38 26,21 26,27 Minimum 196,88 365,63 45.562,50 174,38 379,69 38.390,63 Maximum 573,75 950,63 116.437,50 618,75 981,56 106.312,50 Figure 6: Failure types in bending strength. A: Test piece without node; B: Test piece with node in the centre. Compression, parallel. No differences between nodal and internodal sections were determined. The obtained compression values are lower than the reported for wooden species growing in Chile. Perez (1983) reported 302 kg/cm² for Populus sp. and 400 kg/cm² for Pinus radiata Paper WS-41 7 of 8 Proceedings of the 51st International Convention of Society of Wood Science and Technology November 10-12, 2008 Concepción, CHILE Table 4. Parallel compression NODAL INTERNODAL Parameter (kg/cm2) (kg/cm2) Average 266,97 267,07 Standard Desv. 48,34 55,81 Variation Coefficient 18,11 20,90 Minimum 170 178 Maximum 355 384 Janka hardness. It’s important to bear in mind that when cutting colihue’s test pieces the outer part of the culm, with a higher density, is removed. Compared with wood, the average values for hardness are low and restrict the use of this material to the production of decorative elements, handicrafts or some parts of furniture. Table 5: Janka Hardness NODAL INTERNODAL Parameter (kg) (kg) Average 346,31 219,85 Standard Desv. 56,65 73,34 Variation Coefficient 16,36 33,36 Minimum 200 119 Maximum 456 380 LITERATURE AMERICAN SOCIETY FOR TESTING AND MATERIALS.