Chapter 16 Processes Used to Form WoodMaterials

Objectives Two basic wood forming processes: bonding and bending. Composition boards: hardboard, insulation board, and particleboard. Particleboards: wood pieces and resin binder. Engineered wood material: reconstituted wood. Plasticizing wood: steam or soaking.

Bonding Processes Bonding processes use heat and pressure to compact particles into sheet stock in the production of wood composite board. Composition boards: 3 major types – hardboard, insulation board, and particleboard. Hardboard: has high tensile strength, high density, and low water absorption. Insulation board: manufactured using pulp wood and bagasse (sugarcane). Water and chemicals are added to turn the fibers into a continuous mat. The mats are fed into a drier, then cut and trimmed to size in sheets. Particleboard: is a panel material composed of small discrete pieces of wood bonded together in the presence of heat and pressure by an external binder. About 40% of the particleboard used today is purchased by the construction industry for flooring underlayment. Most of the remaining 60% is used as core material by the furniture industry.

Lamination Process Lamination is used extensively for the construction of plywood. It involves sandwiching sheets of wood together to form larger pieces. Veneer is thin sheets cut from expensive wood. These sheets are used as the exposed layer that is glued over a core of less expensive wood.

Plywood Plywood is made by gluing a number of layers together at right angles to each other. ANSI (American National Standards Institute) standards specify the species, strength, type of adhesive, and appearance of plywood. Lamination produces much stronger product than solid stock. Bending: Steaming or soaking is a better way to bend wood. The stock is subjected to steam or soaked in boiling water till the moisture content reaches 20%. It is then placed in a forming jig that conforms to the desired shape. It is kept in that position till it cools and dries.

Summary Bonding processes use heat and pressure to compact particles into sheet stock in the production of wood composite board. Composition boards: 3 major types – hardboard, insulation board, and particleboard. About 40% of the particleboard used today is purchased by the construction industry for flooring underlayment. Most of the remaining 60% is used as core material by the furniture industry. Veneer is thin sheets cut from expensive wood. These sheets are used as the exposed layer that is glued over a core of less expensive wood. Lamination produces much stronger product than solid stock. Bending: Steaming or soaking is a better way to bend wood.

Home Work 1. What are the 3 major types of composition boards? 2. What is veneer and where is it used? 3. What is the advantage of lamination?