Blocked hot-melt adhesive granules – causes, effects and solutions

11. März 2025 Tim Charzinski adhesives Kommentar hinterlassen

In production processes where hot-melt adhesives are used, a smooth material feed is crucial. In the case of an increased demand for adhesive, the use of a granulate conveyor is to be recommended.

One problem can, however, considerably disrupt the process: blocked granulate. If adhesive granules stick together or clump, this can hinder the automatic conveying, clog the machines and cause production downtime. But why does this happen – and how can the problem be avoided?

What does blocking mean?

Blocking describes the undesired clumping or sticking together of granulate particles during storage or transport. This results in the adhesive no longer being free-flowing and hinders the flow of material in the melting device.

1. Temperature

High temperatures – particularly in summer or improper storage – can cause the surface of the granulate to melt slightly and become sticky. When the granules then cool down, they stick together.

2. Pressure (weight load)

The greater the amount of granulate stored, the higher the load on the lower layers. Particularly when stored on pallets (up to 750 kg/m²), this pressure can compress the granulate and promote blocking.

3. Time

The longer the granules are stored under pressure, the greater the possibility that they will clump. This risk is particularly increased in the case of longer transport routes or storage times.

4. Material properties

Hot-melt adhesives are not all alike. Some granules are more prone to clumping than others, due to their chemical composition or surface structure.

5. Powder quantity and distribution

Some adhesive granules are coated with a fine release agent (e.g.talcum) to prevent them sticking. An uneven or insufficient coating can encourage blocking.

Solutions for blocked granules

If, despite all precautionary measures, blocking still occurs, there are pragmatic solutions:

Shake up granulate bags: Mechanical movement can often make the granulate free-flowing again.

Use sieve inserts: A sieve separates clumped particles before they reach the storage bin.

Optimised storage conditions: Cool, dry storage locations prevent the granules from softening and sticking together.

Do you have any questions or would you like to know about the optimal storage and processing conditions for your hot-melt adhesives? We will be happy to advise you!