Generally, four areas have been found to be common sources of delamination:
1) Choice of adhesive:
The adhesive chosen may not be capable of performing adequately for the application. In applications that only see failures rarely, the adhesive is likely to be appropriately chosen. For example, 94CA is a versatile contact adhesive for use in most countertop type laminations but would have a hard time maintaining a strong bond in a stainless steel panel to plywood table used in a steam cleaning operation. Scotch Weld 1357 would be the next step up in performance.
2) Adhesive must be available at the surface over entire area to be bonded:
Manufacturing productivity is a key concern for many customers, but in an effort to increase output, proper adhesive application can suffer. For contact adhesives this usually shows as insufficient adhesive applied in some areas where delamination occurs. For materials that can absorb adhesive a heavier coating or a second application of adhesive is necessary for consistent results. Adhesives like Holdfast 70 or Hi Strength 90 that spray with a web or lace pattern do better on textured substrates like foams or OSB plywood. A mist spray give a finer spray that can soak into some materials but is good for applications where a smooth finish is desired such as Super 77 & 94CA
3) Bonds must be completed within the correct time frame:
Bonding range is a term used when using contact adhesives. It is defined as the time range recommended to make the bond. If bonds are completed too soon, solvent or water can be trapped within the bond resulting in bubbling. Or if bonds are completed too late the adhesive will be unable to knit (auto adhere) to itself. The bonding range is available in directions for use on the label or in the technical data sheet. The drying of the adhesive and therefore the bonding range is affected by the amount of adhesive applied, the temperature, humidity, and air movement in the application area.
4) Sufficient pressure must be applied to materials to achieve complete contact:
Without the materials touching a bond cannot occur. Further the pressures required to effect complete contact can vary greatly with the materials involved. It is vital that sufficient pressure is applied to the entire area to be bonded. Rarely if ever, is hand pressure adequate.