Basic properties of Chimonobambusa utilis and its spatiotemporal variations

  Objective  This paper aims to further improve the high value-added utilization of culm resources of Chimonobambusa utilis, the chemical components, physical and mechanical properties were investigated, and the variation regularity with age and axial part of bamboo culm were also revealed.

  Method  In this study, the natural plants of Chimonobambusa utilis were used as raw materials to determine the chemical component (mass fraction in this article) content and physical and mechanical properties, such as density, dry shrinkage, compressive strength parallel to grain, modulus of rapture (MOR), modulus of elasticity (MOE) and hardness according to the national standards. The crystallinity of cellulose and microfibril angle was calculated from the results of X-ray diffraction.

  Result  The content of each chemical component of Chimonobambusa utilis varied slightly with the age and axial part, and the variation pattern was not significant. The crystallinity increased with the age of bamboo and then decreased gradually, with a maximum of 50.39% at 2 years old, and increased gradually with the increase of axial part. The microfibril angle decreased and then increased with increasing age and axial part, and the smallest angle was 9.10° in the middle of 2 years old. The basic density ranged from 0.513 to 0.693 g/cm³, the oven-dried density ranged from 0.535 to 0.725 g/cm³, and the air-dried density ranged from 0.556 to 0.756 g/cm³. All densities showed an increasing trend with increasing age and axial part, and increased significantly between 1 and 2 years, and then increased steadily to stabilize. The oven-dried and air-dried shrinking ratio showed a decreasing trend with the increasing age and axial part, and decreased significantly between 1−2 years, and then decreased steadily, the latter fluctuating relatively more. The compressive strength parallel to grain ranged from 50.73 to 64.58 MPa, MOR ranged from 114.09 to 134.26 MPa, and MOE ranged from 8.45 to 12.42 GPa, all of which showed an increasing-decreasing-increasing trend with increasing age, and an increasing trend with increasing axial part; the mean values of inner and outer hardness ranged from 60.00 to 72.70 HD, which showed an increasing trend with increasing age and axial part. The dry shrinkage, compressive strength parallel to grain, MOE and hardness of Chimonobambusa utilis were significantly affected by anatomical index and major chemical components.

  Conclusion  Both bamboo age and axial part of culm affected the basic properties, but the effect of bamboo age was more significant. The culm material of Chimonobambusa utilis was basically mature over 2 years old, which could be the optimized cutting age of Chimonobambusa utilis. In addition, there were some significant correlations between physical-mechanical properties and anatomical structure index.