LAMINATE MANUFACTURERS ASSOCIATION

Reg. No. :G 10307

T.F., 301, Shubham Complex, Sunrise Park, Vastrapur, Ahmedabad-380 015

GUIDELINES FOR APPLICATION OF ADHESIVE AND PASTING FOR PRODUCTION OF HIGH QUALITY LAMINATES AND TO AVOID BUBBLES

CHARACTERISTICS OF LAMINATES

Like wood, a High Pressure Decorative Laminate (HPDL) has grain direction and its dimensional behaviour is similar to that of wood. When humidity in the atmosphere changes width of the laminate undergoes greater dimensional change than the length by a ratio of approximately 2:1. In brief, when the humidity decreases, laminate sheet contracts and when the humidity increases, laminate sheet expands.

GUIDELINES FOR APPLICATION OF ADHESIVE FOR PRODUCTION OF HIGH QUALITY LAMINATES

A variety of adhesives have been found satisfactory for bonding decorative to core materials. The choice of adhesive is based upon the service for which the assembly is intended and upon the bonding facilities available. In all cases adhesive manufacturer’s instructions for application should be adhered to:

Synthetic resin adhesive water based white glue.
Or
Equivalent / Synthetic
resin adhesive
Or
Equivalent / Synthetic rubber based adhesive contains solvent
Or
Equivalent / Synthetic rubber based adhesive contains solvent
Or
Equivalent
1) Surface / Should be properly leveled / Should be properly leveled / Should be properly leveled / Should be properly leveled
2) Coating / Should be on both the surfaces / Should be on both the surfaces / Should be on both the surfaces / Should be on both the surfaces
3) a) Humidity / Should be used in normal humidity / Should be used in normal humidity / Can be used in higher humidity / Can be used in higher humidity
3) b) Humidity more than 80% / Should not be used / Should not be used / Can be used / Can be used
4) Pressure used / Under Pressure / Under Pressure / Under Pressure / Under Pressure
5) Duration / 6 - 8 Hours / 2 Hours / 30 Minutes / 20 Minutes

Note:

In case of highly porous surface like particle board it is advised that a thin coat of adhesive (water based synthetic resin adhesive white glue) should be applied on the surface with pressure and should be allowed to dry completely. After drying light sanding should be done to level the surface. Then second coat for bonding the material should be applied. In case of Marine/Treated Plywood care should be taken to remove any excess deposition of treatment chemical on the surface. This can be done by light sanding and wiping out with a damp cloth.

The time to achieve handling strength and complete curing varies with moisture content of wood, relative humidity in atmosphere and ambient temperature. In case of very high humidity, i.e. more than 80%, it is advisable not to undergo any bonding job. However if you need to bond under any inevitable circumstances, please use adhesive (synthetic rubber based adhesive containing solvent).

CAUSES AND RECOMMENDATIONS FOR AVOIDING FAILURES:

A)  PROPER LEVELLING OF THE SURFACES TO BE BONDED:
The surfaces to be bonded should be properly leveled, free from oil/grease/dust and excess moisture. For best results roughen the surfaces to be bonded.

B)  INSUFFICIENT AMOUNT OF ADHESIVE ON EITHER OR BOTH THE SURFACES TO BE BONDED:

When ready for bonding, the spread film of most contact adhesive will exhibit a uniform semi-gloss appearance over the entire surface of the material 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, recoating the surfaces should be done to achieve a uniform coating. Double coating the edges with adhesive is advisable because of the higher porosity of the substrate edge.

C)  INSUFFICIENT BONDING PRESSURE

To insure intimate contact 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 this process. Hand pressure rolling may prove adequate provided the operator exerts maximum pressure by means of a two handled or single long handled roller. The rollers should be of steel or hard solid rubber (50 – 80 durometer) and not over 75 mm (3 inches) wide. 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.

D)  BONDING WHEN ADHESIVE SURFACES ARE OVER-DRY OR UNDER-DRY

Care should be taken to follow the manufacturer’s recommendations concerning the allowable tack range of adhesive. Of assembly’s made before the adhesive is dry or after the allowable open tie is exceeded, an unsatisfactory bond may result.

E)  TEMPERATURE FOR BONDING OF SURFACES

Unless otherwise indicated by the manufacturer, the temperature of the gluing area and all materials should be 21 degree C (70 degree F) or above.

F)  BONDING OF SURFACE WHERE HUMIDITY IS TOO HIGH

Experience has shown that when the relative humidity is above 80 percent at temperatures of 21 degree C (70 degree F) or lower, moisture may condense on the surface during drying (known as “blushing”) and will prevent an acceptable bond. Hot spray or forced air drying may be used to help prevent this condition.

G)  IMPROPERLY PREPARED OR DIRTY GLUING SURFACES:

The surfaces should be clear, dry and free of oils or other contaminants, such as dust, loose paint particles, and so forth. The adhesive coat-film should have full contact with surface to which it is applied in order to give maximum adhesion.

H)  ADHESIVE NOT STIRRED THOROUGHLY

The adhesive should be stirred thoroughly before use. This is particularly necessary with large containers.

I)  FIELD BONDING OF OVERSIZED SHEETS

It is recommended that the maximum sheet size used for vertical field application be limited to 610 X 2400 mm (2 X 8 feet). If larger panels are required, these should be fabricated.

For, Indian Laminate Manufacturer’s Association

Jikesh Thakkar

HON. SECRETARY