The embira bark fiber: a sustainable Amazon tape

The embira bark fiber is routinely used in Brazil to construct simple structures because of its ease of extraction, flexibility, and considerable strength. It plays an important role, somewhat similar to duct tape, and is commonly used for temporary repairs and tying objects. The flexible bark is removed from the tree by making two cuts into it and manually pulling off the fibrous structure. Three similar but distinct embira bark fibers are characterized structurally and mechanically: embira branca, embira capa bode, and embira chichá. The bark separates readily into strips with thicknesses between 0.3 and 1 mm, enabling it to be twisted and bent without damage. The structure consists of aligned cellulose fibers bound by lignin and hemicellulose. Thus, it is a natural composite. The tensile strength of the three fibers varies in the range of 25 to 100 MPa, with no clear difference between them. There is structural and strength consistency among them. The mechanical strength of embira branca is measured for different fiber bundle diameters and is found to increase with decreasing diameter. Thermogravimetric analysis showed that degradation of the fibers initiates at 250 °C, consistent with other lignocellulosic fibers. X-ray diffraction identifies two major components: the monoclinic crystalline structure of cellulose and an amorphous phase; the crystallinity index is approximately 50%. The tensile strength shows significant variation, a characteristic of biological materials; this can be significantly improved by selective growing of embira-bearing trees.