Optimum conditions for use:
High Pressure Laminates should be properly conditioned to the ambient conditions of the surroundings before they are used. For eg., High Pressure Decorative Laminates and the substrate need at least 48 hours to get acclimatised. Provision should be made for the circulation of air around the components.
Recommended conditioning temperature is about 24°C. Laminates should be conditioned at 45% to 55% relative humidity.
Sawing: To avoid chipping, it is important that the saw blade teeth cut into the decorative face.
Always provide support to the material near the point of blade contact to avoid vibration that causes chipping. Blades with trapezoid tooth configuration and both tungsten carbide and diamond tip blades have proved to be excellent tools for sawing high pressure decorative laminates.
Routing may be done with electric or air powered carbide tip routers. Router speed should be maintained at 16000 to 22000 rpm. It is important to use a router having adequate horsepower to maintain cutting speeds (based on the type and amount of material to be cut). For special edge trimming, very high speed routers are available which produce smooth-edge chip-free work. Sharpness of the router cutters should be maintained.
Belt sanders may be used to flush the self-edge before the laminate top is applied. However, care should be taken to direct the sanding operation away from or parallel to the decorative surface.
A variety of adhesives have been found satisfactory for bonding decorative laminates to core materials. The choice of adhesive should be based on the service for which the assembly is intended and upon the bonding facilities available. In all cases, the adhesive manufacturer’s instructions for use should be followed closely.
Contact adhesives may be used for bonding laminates to a variety of substrates. Contact adhesives do not restrict the movement of the laminate caused by varying humidity conditions to the same extent as thermosetting adhesives. They are particularly useful for application to metal or other impervious surfaces. There are two primary types of contact adhesives – solvent based and water based. Water-based adhesives are not suitable for bonding laminates to non porous substrates. The solvent or the water must be evaporated before satisfactory bonding can be accomplished.
Polyvinyl acetate types (White glue):
Polyvinyl acetate (PVA) emulsion adhesives may be used for bonding laminates to wood substrates where resistance to moisture and high heat are not required in the application (e.g. furniture, kitchen cabinets and office partitions). Catalyzed PVA offers improved moisture and heat resistance
Urea-formaldehyde adhesives are satisfactory for most applications. Resorcinol and phenol-resorcinol adhesives are recommended for use when moisture resistance and heat resistance are required. Epoxy adhesives are liquids with no volatile components. They have good gap-filling and low shrinkage properties and are used mainly for bonding laminates to impervious cores such as steel.
Hot melt types:
Hot melt adhesives are suitable for use only in edge banding operations because of their low heat resistance.
Urethane adhesives are liquids with 100% solids and no volatile components. They have good gap filling and low shrinkage properties. These are used mainly for bonding laminates to impervious cores such as metal, glass etc.
The protective film where applied should be removed as soon as the application is complete. If the film is left in place after fabrication, exposure to strong lights for a period may cause a pale residue and make it difficult to remove the protective film.
Proper bonding recommendations:
- The surfaces should be clean, dry, and free of oils or other contaminants, such as dust, synthetic particles, and so forth. The adhesive film should have full contact with the surface to which it is applied in order to give maximum adhesion
- The adhesive should always be stirred or agitated before use. Sufficient amount of adhesive should be applied on either or both the surfaces to be bonded. When ready for bonding, the spread film of most contact adhesives will exhibit a uniform semi-gloss appearance over the entire surface of the materials to be bonded. Marked variation in appearance will generally indicate an improper or non-uniform adhesive spread. The substrate can generally be seen more readily through those areas where insufficient adhesive has been applied. If this occurs, re-coating the surfaces should achieve a uniform coating. Double coating the edges with adhesive is advisable because of the higher porosity of the substrate edge
- Sufficient bonding pressure to ensure intimate contact is necessary for an adequate bond. Sufficient pressure should be applied over the entire area using as much pressure as possible without damaging the assembly. Pinch rollers (rotary press) and heavy weighted rollers are ideal for such purposes. Hand rolling should be done from the center to the edges to ensure the removal of all air bubbles. The edges should be rolled twice
- Care should be taken to follow the manufacturer’s recommendations concerning the allowable tack range of the adhesive. If assembly is made before the adhesive is dry or after the allowable open time is exceeded, the bond may not have satisfactory results
- Unless otherwise indicated by the manufacturer, the temperature of the gluing area and all materials should be maintained around 21°C (70°F) or above
- Experience has shown that when the relative humidity is above 80% at temperatures of 21°C (70°F) or lower, moisture may condense on the surface during drying (known as blushing) and this will prevent an acceptable bond. Hot spray or forced air drying may be used to help prevent this condition
- It is recommended that the maximum sheet size used for vertical field application be limited to 610×2440 mm (2 x 8 ft). If larger panels are required, these should be fabricated in the shop
- A gap of minimum 2 mm should be maintained between two laminates while pasting side by side