Study of Compression Conditions on Compression Set in Treated Paulownia with Phenol Formaldehyde

Paulownia is one of the fast-growing species that was attended to supply industrial requirement in recent years. The application of this species is limited because of low density, so wood modification via compression and densification is an effective method. For this purpose, the paulownia boles were prepared from Shastkalateh forest and cut into blocks with 60×20×20 mm dimension. The variable factors of this test were effective factors in press process consist of compression percentage and direction and percentage of compression, press time and press temperature. Specimens were impregnated with 10% concentration PF resins before compression. Densification was done at 3 percentages (30%, 40% and 50%) and two directions (radial, tangential). Pressing process were done at two temperature levels (170 and 190^oc), and two periods of time (8 and 12 minute) residual compression was determined after 24 hour submerging in the water. Results showed that compression percentage and direction in modified wood had significant difference compared with control samples. But the effects of press temperature and time were not significant. The best treatment for paulownia wood was obtained in radial direction and 50% compression. But it depends on conditions.