While aqueous solutions, dispersions and emulsions have been the most commonly used adhesives in the packaging industry,¹ there are many settings in which hot-melts and other products are preferred. Thats in part down to one major weakness in waterborne formulations - long setting times, caused by the need for water to evaporate.² However, in recent years researchers have striven to overcome this, and have gone some way towards rectifying the deficiency.

Waterborne adhesives are often used in packaging in conjunction with paper and board materials. Due to their relatively low viscosity, water-based adhesives can be sprayed or extruded in a thin layer that forms a strong adhesive bond. Their low viscosity also means that they can penetrate porous substrates, rapidly giving a high degree of tack and stronger bonding than is achievable with hot-melt adhesives.

While hot-melt adhesives soften at temperatures over 75°C and may become brittle near 0°C waterborne adhesives remain bonded strongly over a greater temperature range. They can also make packaging, for example corrugated containers, that can be re-pulped and recycled without removing or separating the adhesive layers, another distinct advantage over hot-melts.

Yet, in applications like sealing corrugated fibreboard containers made from pre-cut flats, setting time remains the most critical property. Under the type of compression typically used on carton sealing lines, a hot-melt adhesive will set in about 1 to 3 seconds, as compared with 10 to 20 seconds for a water-based adhesive.