The effect of expanded polystyrene on the heating of particle-polymer package

Abstract

This paper is devoted to the study of the influence of expanded polystyrene on the heating of the particle-polymer package during the hot pressing of lightweight particleboards. To fix the temperature, to which the middle layer of the particle-polymer package is warmed, a thermocouple was placed in the middle of the package. The hot pressing was made at a temperature and specific pressure levels of 200°C and 2,4 MPa, respectively. The lightweight particleboards (without expanded polystyrene and containing expanded polystyrene 4, 7, 10 %) overlaid by rotary-cut veneer were manufactured with dimensions of 300×300×18 mm and density of 350, 450 and 550 kg/m3. It was established that duration of the heating of the particle-polymer package of lightweight particleboards decreases with an increase of the amount of expanded polystyrene to 7%, and then begins to grow. Adding expanded polystyrene to particles causes the filling of voids with the simultaneous increasing the number of contacts between the particles through them the heat is transferred from the periphery to the middle of the particle-polymer package. An increasing the content of expanded polystyrene in a particle-polymer package of more than 7% leads to a slowing down of its heating due to the fact that the volume of expanded polystyrene is higher than volume of particles, and the thermal conductivity of the expanded polystyrene is lower than that of wood. With an increase in the density of the boards from 350 to 550 kg/m3, the duration of heating of the particle-polymer package decreases. Most of the mass of particles per unit package volume reduces its porosity, increases thermal conductivity and, as a result, causes it to warm up faster. The values of the time of heating of the middle layer of lightweight particleboards with a content of expanded polystyrene of 7% to 100 °С is lower by 12-33%, than those without expanded polystyrene. The application of the study results allow to increase the efficiency of the hot pressing of lightweight particleboards containing expanded polystyrene.

Keywords

• lightweight particleboards
• expanded polystyrene
• rotary-cut veneer
• wood particles
• urea formaldehyde adhesive
• thermal conductivity
• temperature gradient.