Flakeboard Thickness Swelling. Part I. Stress Relaxation in a Flakeboard Mat

Robert L. Geimer, Jin Heon Kwon, James Bolton

Abstract


The steam injection schedule best suited for dimensionally stabilizing a flake mat is one in which steam treatment is initiated before the press is closed and is continued at least until the mat attains target thickness. Experiments showed that resinless mats treated with 20 sec of steam at 600 kPa had maximum thickness swelling of 205% compared to 350% for resinless mats pressed in a conventional fashion. Reductions in thickness swelling were proportional to steam duration and pressure. Mats treated with 20 sec of steam at 1,950 kPa had only one-tenth the thickness swelling measured in conventionally pressed mats. We believe that reduction of thickness swelling is dependent on a number of factors, including plasticization of the wood, "lignin" flow, and molecular changes in the wood structure.

Keywords


Flakeboard;steam injection;thickness swelling;dimensional stability;springback

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