Why Does Hot Melt Adhesive String During Application?

Hot melt adhesive may string when the adhesive's viscosity, temperature, flow behavior or application equipment is not properly matched to the production process.

Common causes include:

• Unsuitable adhesive temperature

• Adhesive viscosity that is too high for the application

• Incorrect nozzle, valve or glue roller settings

• A mismatch between adhesive flow and production speed

• Adhesive buildup or contamination on the application equipment

• Excessive residence time of adhesive in the application system

• Incompatibility between the adhesive grade and application equipment

The troubleshooting process should begin by checking the recommended processing conditions for the specific adhesive grade.

Temperature, adhesive flow, production speed and equipment condition should then be checked systematically. Changing several parameters at the same time can make it difficult to identify the actual cause.

For PUR hot melt adhesive, proper storage, handling and equipment cleaning are particularly important because the adhesive can react with moisture before or during processing.