Why are my boxes popping open?
Typically, pop-opens come from too little glue or glue applied too cool (poor penetration, little or no fiber tear), too much glue or glue too hot so it is still soft when compression ends, short or uneven compression, a change in board, or cold storage the grade was not made for. Pull a failed flap and look at it before changing settings.
A good hot melt case seal typically shows fiber tear: when you pull the flap, paper fibers come away with the glue. No fiber tear means the glue never wetted into the board.
Hot melt and hot equipment can cause burns. Follow your equipment maker’s safety manual and lockout steps; qualified personnel only. Call us for data sheets
Read the failed bond
| What you see | Likely cause | What to try |
|---|---|---|
| Glue on one side only, smooth, little or no fiber tear | Glue too cool, too little glue, or open time too short for the board | Raise temperature within range, check nozzle size and pressure, check for cold board |
| Glue on both sides, stringy, flap sprang open off compression | Glue still soft when compression ended: too much glue or too hot | Reduce bead size or temperature; lengthen compression |
| Bead flattened, fracture lines, failed in cold storage | Cold crack: grade not made for the cold | Use a freezer grade. Call 800-249-0337. |
| Uneven beads, some flaps hold and some fail | Plugged or worn nozzle, uneven guns, temperature swings | Clean or replace nozzles, keep the tank full and covered, keep hoses off a cold floor |
| Failure started with a new board lot | Coated, high-recycled or high-memory board | Trial a grade with faster hot tack; send us the board |
Board and the cold
High-memory, coated and high-recycled boards push back harder against the bond. Cattie’s metallocene hot melts are made with fast hot tack, which typically helps limit pop-opens on high-memory board. For cold chain, Cattie’s freezer grades 8280 and 8365 typically hold to about −40°F (grade-specific). Freezer and deep-freeze grades are listed on packaging adhesives.
What to send us
A failed case or a clear photo of the flap, the board spec, the grade you run now, setpoints, compression time, line speed, and where the cases go (ambient, cooler, freezer, hot truck).
Request a sample Call 800-249-0337 Request a quote
Related
How to solve hot melt application problems · Hot melt application trouble-shooting tips · Hot melt system trouble-shooting tips · Hot melt adhesive · Stringing · Charring and gelling · EVA vs metallocene
Pop-open and fiber tear FAQ
What is fiber tear?
Fiber tear is paper fiber that pulls away with the hot melt when you open a sealed flap. Good fiber tear typically means the glue wetted into the board and the bond is stronger than the board surface.
Why do cases pop open coming out of the compression section?
Usually the glue is still soft when compression ends, from too much glue, glue running too hot, or compression that is too short. Too little or too-cool glue can also fail there. Read the failed flap to tell which.
Why do cases pop open in the freezer?
A grade not made for the cold can crack. Look for a flattened bead with fracture lines. Cattie freezer grades 8280 and 8365 typically hold to about −40°F (grade-specific).
Can a new board cause pop-opens?
Yes. Coated, high-recycled and high-memory boards are harder to hold. Send us the board and we will match a grade. Call 800-249-0337.
