Hot Melt Sticks

Most people are familiar with hot melt stick adhesives and hot melt glue guns used for craft projects.  For industrial use, glue guns are available with higher melt rates and improved durability and the adhesive is supplied in larger sticks. Adhesive is melted and applied as the stick of adhesive is advanced into the back of the applicator melt chamber. Handheld hot melt applicators are ideal for multi-station assembly or intermittent use since they require low initial investment and low maintenance. For smaller applications, only low melt rates and volumes of adhesive are needed and applicators that utilize hand pressure to deliver the adhesive can be used. For larger applications, larger applicators that utilize pneumatic systems to deliver adhesive are used. Adhesive is typically applied in beads which hold heat long enough to allow assembly of components. Special tips are available to apply single or multiple beads of adhesive. These are particularly useful for sealing corrugated cartons where the tip is also used to guide the application of adhesive along the flap of the carton.

Because the application of adhesive and assembly of components is done by hand, formulations for use in glue guns need to have longer open time (set more slowly on cooling) than hot melts used in automatic equipment. This allows more time for the adhesive to be applied and parts assembled. Some hot melt stick adhesives have been developed with extended open time to allow them to be spray applied for bonding larger areas.  A limited amount of pressure is available for dispensing adhesive when glue guns are used so there is a limit to the adhesive melt viscosity for use in these applicators.  In addition, hand application and assembly allows the possibility for workers to come in contact with the hot applicator tip or molten adhesive.  Traditional hot melts are applied at 350 to 425oF (175 to 220oC).  Proper procedures and safety equipment should be used to avoid the potential for burns. To address this concern, a family of hot melts has been developed that allows application at temperatures as low as 250oF (125oC).  Although burns can still occur if skin comes in contact with molten adhesive, the lower temperature generally results in only reddening or a minor burn.  Performance of these lower application temperature adhesives is similar to many higher application temperature adhesives but is not as good as the highest performing hot melts.  However, they are adequate for many industrial applications.