During the construction of particle board in the extrusion pressing process, what is the orientation of the wood particles with respect to the plane of board?
Manufacturing Particle Board
Particle board is an engineered wood product made from wood chips, sawmill shavings, or even sawdust, mixed with a synthetic resin or another suitable binder. This mixture is then pressed and extruded. The method of pressing is crucial as it determines the internal structure and properties of the board.
- Platen Pressing: Pressure is applied perpendicular to the face of the board. This orients the particles parallel to the board's surface (0°), creating a stronger board.
- Extrusion Pressing: Pressure is applied along the edge of the board, pushing the material through a die. This is the process described in the question.
📝 Detailed Analysis of the Options
(a) 45°, (b) 30°, and (d) 0°
An orientation of 0° (parallel to the plane) is characteristic of flat-platen pressed boards, not extruded boards. Other specific angles like 30° or 45° are not the primary orientation resulting from the extrusion process. The forces involved in extrusion lead to a distinct perpendicular alignment.
(c) 90°
This is the correct answer. In the extrusion pressing process, the mixture of wood particles and resin is forced through a die. The pressure is applied parallel to the length of the board being formed. This force causes the wood particles to align themselves predominantly in a direction perpendicular (at a right angle or 90°) to the plane (face) of the board. This results in a board that has good dimensional stability but is generally weaker than platen-pressed boards.
📊 Particle Board Pressing Methods
| Pressing Method | Direction of Pressure | Resulting Particle Orientation |
|---|---|---|
| Platen Press | Perpendicular to the board face | Parallel to the board face (0°) |
| Extrusion Press | Parallel to the board length (along the edge) | Perpendicular to the board face (90°) |
💡 Study Tips
- Extrusion = Pushing Out: Think of extruding something like toothpaste from a tube. The force is along the length. In board making, this lengthwise force turns the particles sideways.
- Platen = Pressing Down: A platen press works like a giant flat stamp, pressing down on the face of the board. This flattens the particles, aligning them with the face.
- 90° for Extrusion: This is the key association to remember. The extrusion process results in particles oriented at a right angle to the board's surface.