Physico-chemical and mechanical characterisation of the bark of selected ficus species growing in Uganda

Abstract

The bark of Ficus trees is underutilized and often linked to Cultural norms yet it can be a driving force for continuous planting of Ficus trees. In this study, the physical, chemical and mechanical properties of the bark of three Ficus species growing in Uganda were investigated. The objectives of the study were: (i) to determine the basic density and water absorption rate of the bark of F. natalensis, F. thonningii and F. glumosa; (ii) to evaluate the cellulose and lignin content of the bark of the three Ficus species; and (iii) to assess the tensile strength of the bark of the three Ficus species. Bark samples of the three species i.e Ficus natalensis (K1), Ficus thonningii (K2) and Ficus glumosa (K3) were collected, the outer bark was scrapped off and inner bark analysed. The water absorption rate was determined according to ASTM D570 (1998) while density was determined using the standard water displacement method. The cellulose content was determined using analytical biochemistry method by Updegroff (1969). The Lignin content was determined using Klason lignin according to COST FP0901 (2011) similar to TAPPI T 222om (2002) and TAPPI UM 250 (1991). The tensile strength of the bark was determined according to ASTM D5035 (1995) using an Instron testing machine of load 25KN. Basic density, lignin content and tensile strength were highest in the bark of F. natalensis, and lowest in F. glumosa. Water absorption rate and cellulose content were highest in the bark of F. glumosa and lowest in F. natalensis. Based on the lignin content for all Ficus species studied, the bark is not suitable for use in industries such as paper manufacturing where lignin is undesirable. The high water absorption rate of the bark of Ficus glumosa makes it a suitable candidate for the manufacture of indoor products.