Slip and Anti-Block — Controlling COF Without Losing the Print
Direct answer
Slip and anti-block solve two different problems that are usually bought as one package. Slip agents — erucamide and oleamide — migrate to the surface and lower the coefficient of friction so film runs through formers, collars and sealing jaws. Anti-block agents are inorganic particles that create microscopic surface roughness so two film faces cannot wring together and vacuum-lock. Adding more slip does not fix blocking, and adding more anti-block does not fix a film that will not slide over a former. Diagnose which one is failing before changing a recipe.
Reading the line, not the datasheet
- Film will not open on the bag machine, but slides fine — a blocking problem. Increase anti-block particle loading or move to a larger mean particle size.
- Film opens fine but drags on the collar and gives seal wrinkles — a COF problem. Slip level or slip migration time.
- COF good on day one, poor after three weeks in the roll — slip has migrated into the adjacent wrap or been adsorbed onto anti-block particles.
- COF good on day one, too slippery after two weeks — over-slipped; rolls telescope and pallets slide.
Erucamide vs oleamide, in one paragraph
Oleamide migrates faster and gives an earlier COF drop, which suits fast converting. Erucamide migrates more slowly, is more thermally stable, and holds COF over a longer period and at higher processing temperature, which suits film that will be stored and converted later. Neither survives indefinitely; both are consumed by adsorption onto fillers, pigments and anti-block particles.
The print and lamination conflict
Amide slip is the most common root cause of ink adhesion and lamination bond failure in polyolefin film. The bloomed layer is a low-surface-energy release coating — exactly what you do not want under an ink or an adhesive. Where the film is printed or laminated, the practical routes are a lower slip loading with higher anti-block, a non-migratory slip system, or corona treatment applied immediately before printing rather than at film production. Corona treatment also decays over time in the presence of amide slip, which is why a film that printed well last month can fail this month with the same treatment level.
Specify it properly
State kinetic COF target film-to-film and film-to-metal, the acceptable measurement window after production, whether the film is printed or laminated, the seal temperature range, and whether the application has food-contact or optical clarity requirements — natural silica, synthetic silica and talc differ markedly in haze contribution.
What we supply
Allzone supplies a combined anti-block and slip masterbatch on a PP/PE carrier at a 1–5 % addition rate, per the supplier technical data sheet held on file. Target COF and application must be stated at enquiry so the right variant is quoted.