Particle board is a wood-based panel product manufactured under pressure and temperature from the particles of wood or other any lignocellulose fibrous materials and a binder based on UF, PF or with some natural adhesive. Therefore, in the building industry, a range of several different products based on the application of raw organic materials have already been experimented. Among these organic based building materials, wood and wood engineered products are perhaps the most commonly applied ones. However, different agricultural products have also been reported as possible raw organic building materials such as bagasse, cereal, straw, corn stalk, corncob, cotton stalks, kenaf, rice husks, rice, corn or maize cobs, straw, sunflower hulls and stalks, banana stalks, coconut coir, bamboo, durian peel, and palm leaf, among others. Applications for this agriculture waste may result in an alternative and sustainable product that may be relevant.
Furnish moisture content exerts much influence both on the manufacture and the properties of Particle board. Too high or low levels of furnish moisture result in troublesome operation and produce a poor quality board. The optimum moisture content depends on many factors such as geometry, and wood density. The maximum board strength occurs when the moisture content ranges between 8 to 12 percent at the particle interface. Generally, it is advisable that the boards made from low density woods possess a relatively lower moisture content compared to boards made from denser woods. To make a board of a given density and volume using a low density wood species will require a large number of particles.
Thus excessive moisture in mat made up of low density particles is likely to lead to low board strength or, in extreme cases, results in blows and blisters. Moisture differentiation can result in a number of advantages during the hot pressing operation with such as rapidly consolidating the mat surfaces into a dense, strong layer. In order to create a moisture differential, either surface particles with higher moisture are used or, just prior to hot pressing, the mat surface is sprayed with a given quantity of water per unit surface area. An optimum exists in the amount of water sprayed, depending on such factors as shape and size, and mat moisture content.
Short, thick particles normally used in the core layer require a greater amount of resin per unit surface area as compared to long, thin particles or very fine granular particle used for surface layers. Longer and thinner particle, everything else being the same, produce a board with higher bending strength and dimensional stability. Shorter and thicker particles produce a board with lower bending strength and dimensional stability but higher internal bond strength. The placing of particles to produce a board with high bending and internal bond strength the thick and short are used in core layers while the thin and long are used on the surface layers.
It has been investigated the ratio of particle thickness in the middle layer over particle thickness in the surface layer for its effect on the formation of the density profile of three-layered Particle board. A high ratio, indicating that the middle layer consists of thick particles, leads to higher density of the surface layer, as thick particles generate higher restoring forces, while the fine particles in the surface layers can be plasticized and formed more easily, leading to higher compaction in these zones. The use of thick particles in the panel core thus enhances both, the IB strength.
A further benefit from this strategy is the generation of a smooth panel surface for downstream laminating or coating works.The variation of the mass ratio of the fine surface to the rough core layer is also a means of shaping the density profile. At higher ratio, which means an increase in the proportion of surface layer, the zone of higher density grows which due to the conservation of mass leads to a decrease in core density. In this configuration, the core layer gets thinner and lighter at the same time.
While particle length and thickness have been identified as decisive factors for the mechanical properties. The orientation of the particles in relation to the test direction has a high impact on the mechanical properties of Particle board. The alignment of the particles in the long axis of bending specimen’s yields considerably higher MOR compared to perpendicularly aligned particles.The size of the particles influences the Resin Load (RL), which is most commonly referred to as the ratio of dry resin applied on dry particles, as the surface area relevant for adhesive application varies at different particle sizes. Referring to particle sizes typical for Particle board production.
As per literature 100 gm of rough particles possess a surface area of 1 m² whereas 100 gm of fine particles have a surface area of 10 m². Thus, for fine particles the RL must be chosen at higher level. The RL requires special attention in the case of adhesive application on a particle mix of different sizes. The roughness of the particle surface also influences the resin load. The smoother the particle surface is and the better its natural structure is preserved, the higher the shear strength of the bond between the particles gets. Rough particle surface hence implies the need for more resin to achieve satisfactory bonds.
Particle geometry (shape and size) is a prime consideration affecting both the board's important properties and its manufacturing process. Indeed, the performance of Particle board is, in large part, the reflection of particle characteristics Mechanical strength is an important property of the board and is greatly affected by particle geometry. Particle geometry affects the face and edge appearance significantly. Thin and small particles with their pliability and gap filling ability generate gap- free-surface. In recent years, most commercial operations have utilized fine, dust like particles and pressure- refined fibers on board surfaces. Particle geometry indirectly influences the finishing, gluing, and overlaying characteristics of Particle board. Further, the behavior of Particle board to machining (i.e., sawing, routing, shaping, planning, and sanding) is also affected by the type of particle used in manufacturing the product. The shape and size of particles have a direct influence on the amount of heat required for the particles to reach a certain level of moisture content. An increase in particle size of any specific shape necessitates a greater amount of heat to remove a given weight of water.
High quality particleboards with a high strength, smooth surface, and equal swelling are normally obtained by using a homogeneous material with a high degree of slenderness (long and thin particles), but without oversized particles, splinters, or dust. Thinner and longer particles yield a higher aspect ratio, larger surface area, and increased contact area in the glue line, which contributes to a better interaction and thus better strength. Differences in the wood type, shape, and size have been reported to have a remarkable effect on the properties of the produced particleboard.