Gluing High Pressure Decorative Laminates

It is stated that 150 million sq.-ft. of high-pressure-laminate plastic overlay was produced in 1955. Plastic overlays go into a host of products readily accepted by the consumer. Most laminates are produced for resale by independent manufacturers. The plastic laminants are purchased from independent plastic producers. The plastic sheets are glued to a plywood, lumber, or particle board core by one of four methods: 1) Hot press method. This method is not widely used due to large capital equipment costs and more difficult production methods, particularly in temperature control. 2) Contact cements. These rapid bonding adhesives approach the perfect production adhesive. One simply coats the surfaces to be glued, combines them runs them through a low-cost pinch roll, and they are available almost immediately for machining. The drawbacks are: a) low shear strength of 1000 psi compared to 3000 psi for ureas, caseins, or polyvinyls, b) six to eight times the cost of conventional adhesives, c) they are volatile in nature and must be stored and handled properly, and d) they are thermoplastic and, must have perfect contact for best bond. 3) Urea and casein adhesives. These have been extensively used since the innovation of high pressure laminants; due to their low cost, they provide durable bonds and they do not present excessive handling problems. Their major drawbacks are: slow speed of set, high abrasive characteristics to cutting machines, lack of flexibility in temperature operating conditions, limited pot life, require glue crew to use protective clothing, require a premix, and if urea is allowed to come into contact with the face of the plastic it will “pick out” the sheet and spoil the top. 4) Polyvinyls. These adhesives have, during the, last 4 years taken over as the major adhesive for the bonding of laminants. They can be used directly as received. The pressing time is intermediate between contact cements and urea adhesives. A 60 psi load for 20-35 minutes followed by 2 to 3 hours of cure is sufficient. Present day challenges are to improve design, improve quality, and lower cost in order to remain competitive. The latter two factors could be attained with a more suitable core material at a lower cost.

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