Foam is used for a wide range of packaging applications. Hot Melts are very effective for bonding foams to packaging material.
In packaging expanded polystyrene (EPS), polyethylene and urethane forms are used to produce packages that offer greater protective qualities to the products inside. These foams are easily bonded to themselves and other substrates such as wood and corrugated paper boxes using standard EVA and APAO hot melts.
Bonding foams to resin, plastic and metallic containers can be more of a challenge as these surfaces are typically smooth. In these instances pressure sensitive hot melts (PSA’s) are often used as they have immediate and long term bonding capabilities. PSA’s should not be used where substantial stress is placed on the bond or where elevated temperatures are the norm unless this is taken into account in the specification of the pressure sensitive hot melt.
There are many methods of applying these hot melts for the attachment of foam substrates to packaging materials. Typically, companies extrude a bead of hot melt in a random pattern and bond the substrates. While this can be sufficient it is not the most effective method of bonding foam. Foams typically have minimal surface strength so spreading the adhesive across the foam bonds a much wider area and offers more long term strength than the beads point of contact bond.
Swirl, spray and roll coating is used to apply hot melts to foam or the substrates the foams will be bonded to. These methods apply a thin coating to the top of the foam or other substrate prior to lamination. The swirling and spraying of hot melt reduces the temperature of the adhesive and is preferred for heat sensitive foam products. While roll coating is fast and efficient is can also be wasteful as large quantities of hot melt can be driven into open cell foam and perform no function in the bonding process.
Prior to assembling your package you should evaluate the range of hot melt adhesives and systems used to apply these products.