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Magnified Bonding Issues. Let’s Take A Closer Look!. Bonding. We can only obtain the perfect bond when there is enough water available at the proper temperature, to fully gelatinize the starch granules.
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Magnified Bonding Issues Let’s Take A Closer Look!
Bonding • We can only obtain the perfect bond when there is enough water available at the proper temperature, to fully gelatinize the starch granules. • Without the correct amount of starch, water and energy available in the proper proportions at the proper time, we cannot even achieve a commercially acceptable bond.
Bonding • Starch granules will gelatinize in the presence of water and heat, thus transforming into a film.
Fully Gelatinized Starch • This is what we should achieve in our glue lines:
Isobar Glue lines Flute tip Gelled Starch No Visible Crystallization.
Conventional Glue Lines Gelled starch Un-Gelled starch
Crystallyzed Starch? No, this is salt… BUT
Crystallized Starch This is STARCH in a conventional operation. If it’s hard and rough like grains of salt it WON’T BOND. Starch excess in the valleys (crystallized). Gelled starch in the fillet zone.
Crystallized Starch This is a typical WHITE GLUE LINE. • All the water left too soon : • By migration into the paper because the paper was too dry and too hot due to excess temperature. • By evaporation because the steam pressure setting in the double backer caused it to flash off before the gelatinization reaction could be completed.
What happens when you run out of water? • Partial bonding: Usually some part of the starch is gelled (center area), but most of it is crystallized, especially at the edges were the water migrates away faster. • This is normally caused by: • Too high a solids content. • Too much temperature in the paper. • Too high a steam pressure in the DB. • Normally (with hot corrugating) you’ll add more starch in order to give more water to the equation. • This will increase the amount of gelled starch because you can SATURATE the paper around the flute tip and still have some water left for PARTIAL gelatinization. • Of course more water also • means you’ll turn UP the heat!
What Should You Do?COOLER CORRUGATING Gives You Another Option. With Cooler Corrugating You Will: • Reduce Paper Temperature. 2. Apply less Starch. 3. Reduce Steam Pressure In The Double Backer. 4. Reduce Starch Solids Content In The Formulation.
COOLER CORRUGATING Gives You Better, Stronger Bonding!With Far Less Starch.Which Glue Line Do You Prefer?