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Shrinkage and Density Studies on Two Bamboo Species.

Y.A. Talukdar
Senior Research Officer
Seasoning &Timber Physics Division, Bangladesh Forest Research Institute, Chittagong.

M.A. Sattar
Seasoning &Timber Physics Division, Bangladesh Forest Research Institute, Chittagong.

Abstract/ Executive Summary:

Shrinkage, bulk density and moisture content of two important indigenous bamboo species, Bariala (Bambusa vulgaris) and Mitinga (Bambusa tulda) were investigated at three heights. Shrinkages in both wall thickness and diameter were found appreciable both at 12 percent moisture content and at ovendry condition. There was variation in shrinkage with the change of height from the butt to the top of culm, but this variation was not found to be statistically significant. Mature bamboos had lower wall-thickness-shrinkage compared to that of immature bamboos. Higher values of diameter-shrinkage were observed in immature Bariala in contrast to those of mitinga.Variation in density and moisture content was observed between the species, as well as, within the species. However, this variation was not statistically significant.

Keywords: Shrinkage, Density, Moisture content, Bariala, Mitinga

Location: Chittagong and Chittagong Hill Tracts

Start Date: 00-00-0000

End Date: 00-00-0000

Program Area: Postharvest and Agro-processing

Commodity: Bamboo

Objectives:

To know the extent of the shrinkage with the variation of density and moisture content of bamboo.

Methodology:

Investigations were carried out with Bariala and Mitinga since these two species are relatively important from the consideration of their utilization. Three mature and three immature culms of each species were collected from selected bamboo clumps of Chittagong and Chittagong Hill Tracts. The maturity of the bamboos was determined arbitrarily from their positions in the clump. Bamboos standing inside the clump were taken to be matured while those growing outside the clump were considered to be immature.The specimens for shrinkage study were prepared from three different heights- butt, middle and top of the culm. The specimens for wall-thickness-shrinkage were in the form of 2.5 cm (1.0 in) long rings while the specimens for diameter-shrinkage were the internodes of the culm of varying lengths bounded by nodes at the extremity. In this way a total of three rings and three internodal columns were cut from each of the bamboo and thus a total of 18 rings and 18 internodal columns were obtained from each of the species.The wall thickness was determined at two perpendicularly marked positions while the diameter shrinkage measured along two diameters perpendicular to each other. The wall thickness and diameter measurements were made with a slide caliper to the nearest 0.005 cm. To equilibrate the samples to 12 percent moisture content all the test pieces were placed in a conditioning chamber maintained at 26.7⁰C and 66% R.H. after taking weights and measurements in green condition. Periodic weights of the samples were taken until a constant weight was attained. Thereafter, the samples were placed in an electric oven maintained at 70⁰C and then gradually raising the temperature at 103⁰C ± 2 in order to avoid drying defects. The samples were weighed at regular intervals until the weights became constant. The measurements in wall thickness and diameter were then taken. A number of samples for diameter shrinkage study were found splitted during drying in the oven.

Samples for moisture content and density determination were taken in the form of a pair of 2.5 cm (1.0 in) long rings from each of the height positions. Density was determined on the basis of both green and oven dry volumes. For the determination of green volume the sample was soaked night-long in water. The sample was then oven dried, weighed and data recorded. The dried sample was soaked in melted paraffin and the oven dry volume was determined. In both the cases the volume was ascertained by the water displacement method.

Source of Information: Bano biggyan patrika, Vol : 9 (1 & 2), Jan-July 1980, 65-70

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Shrinkage in bamboos in the wall-thickness were quite appreciable for both the 12 percent moisture content and the oven dry condition. A variation in shrinkage was apparent but was not found to follow any definite trend. There was no progressive increase or decrease of shrinkage with he increase of height. Thus height factor was not found to be statistically significant on wall-thickness shrinkage. It is also found that mature bamboo had less wall-thickness-shrinkage than immature bamboo. This change of shrinkage was not, however, observed to be statistically significant. It is further apparent that bariala had a lower shrinkage rate compared to Mitinga. This difference of shrinkage was not also significant. In this case too, no correlation could be established between height and shrinkage. The higher values of diameter-shrinkage were, however, apparent in immature Bariala while the reverse was found in case of Mitinga.Density values show that there was apparent difference between the values of mature and immature bamboos. Such differences were also observed between the species. These differences were not, however, statistically significant. Like shrinkage, the density values also did not change with the change of height.

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