Plastic-like moulded products made from renewable forest resources

Abstract

The bark of fast-growing wood species such as Pinus and Acacia species contains a high amount of tannin, a renewable forest resource. In this study, the possibility of utilizing radiata pine tannin as a substitute for synthetic thermosetting resins in the production of moulded products was investigated. When tannin powder and wood flour (tannin : wood flour = 1 : 1 w/w) were mixe and moulded at 190 °C and 100 MPa for 10 minutes, plastic-like moulded products with a modulus of elasticity (MOE) of 9 to 10 GPa and a modulus of rupture (MOR) of 60 to 70 MPa were obtained without further additives. Furthermore, when tannin and wood flour (1 : 1 w/w) were mixed in water and freeze-dried, tannin was partially impregnated into the wood flour, and the MOR of the moulded product increased by more than 10% compared with that of products produced without the impregnation process. The moulded products described above showed good water resistance. Moreover, an increase in wood flour content was found to upgrade the mechanical properties effectively, with a MOR of 90 to 100 MPa being obtained at 75% wood content, despite a reduction in water resistance.