Glue and Bonding Process on Corrugated Lines: The Root Cause of Delamination Is Here

Half of corrugated board's strength comes from the paper and half from the "glue." Get the glue wrong, and the board delaminates the moment it meets moisture — box compression collapses and customer complaints pile up.

The Scenario: Bonding Is the "Backbone" of Corrugated Board

Corrugated board is made by bonding the liner, corrugating medium and inner liner with starch glue. Whether the glue is spread evenly, gelatinized thoroughly and pressed firmly directly determines bonding strength and moisture resistance.

The Pain Points: Delamination, Blistering and Weak Bonding

A wrong starch formula or mismatched gelatinization temperature causes "false bonding" (the surface sticks but the core doesn't); uneven glue application leads to delamination or show-through; insufficient bonding pressure causes the board to separate into layers. These problems erupt together in humid weather.

The Solution: Dial In the Four Bonding Factors

1. Starch glue formula and gelatinization temperature. Corrugated board commonly uses starch glue (corn starch + caustic soda + borax), with a gelatinization temperature generally around 55–65°C. The formula must match machine speed and paper basis weight, and needs fine-tuning with the seasons.

2. Glue application control. The amount must be even and just right — too little won't bond, too much shows through and wastes glue. Calibrate glue-roll gap and pressure regularly to keep the glue line uniform.

3. Bonding pressure and contact. The gap between corrugating roll and pressure roll must be precise, with moderate pressure so the medium and liner bond fully — pressed firm without crushing the flute.

The Result: Firm Bonding, Stable Compression Strength

With the bonding process dialed in, board bonding strength (PAT/PCT tests) meets standard, moisture resistance and compression stay stable, and delamination complaints drop sharply.