Slip vs Anti-Block Masterbatch for Packaging Film
Flexible packaging film must run smoothly through extrusion, winding, printing, bag making, filling and sealing. Two additives frequently used to control this behaviour are slip and anti-block masterbatches.
Although they are often supplied together, they solve different problems. Selecting them by dosage alone can create inconsistent coefficient of friction, poor roll opening, reduced clarity or downstream printing difficulties.
What Does a Slip Masterbatch Do?
Slip additives reduce resistance when a film surface moves across another film surface or machine component. This behaviour is normally evaluated using coefficient of friction, or COF.
Many conventional slip additives migrate toward the film surface after extrusion. Consequently, the final COF may change with time, storage temperature and film structure. Fast- and slow-bloom slip systems behave differently, so a buyer should specify when the film will be converted and when COF will be measured—not just a target value.
What Does an Anti-Block Masterbatch Do?
Blocking occurs when adjacent film layers adhere or become difficult to separate, particularly after winding or stacking. Anti-block additives create microscopic surface separation that helps reduce film-to-film contact.
The appropriate system depends on film thickness, clarity, winding pressure and the required opening behaviour. Anti-block selection can also influence optical properties and surface appearance.
Why One Additive Cannot Automatically Replace the Other
A film may have a suitable COF but still be difficult to open. Conversely, a film may separate easily but move too slowly or too quickly through converting equipment.
Slip and anti-block should therefore be evaluated as a system. The correct balance depends on:
Resin and film type
Blown, cast or oriented-film process
Single- or multilayer structure
Film thickness and winding conditions
Printing, lamination and sealing requirements
Packaging-machine requirements
Storage time and temperature
Consider the Film Layer Structure
In multilayer film, the additive may only be required in one or both skin layers. Adding it throughout the structure may increase cost without delivering a proportional benefit.
The supplier should receive the complete layer structure, the thickness of each layer and the location of printing, treatment, sealing or adhesive application.
Check Printing and Lamination
Surface-active or migrating additives can influence printing, coating and adhesive performance. The film producer should assess dyne level, ink adhesion and bond strength at the actual conversion time.
Testing immediately after extrusion may not represent performance several days later. Retained samples should be evaluated after realistic storage and ageing periods.
Define the Required COF Correctly
“Low COF” is not a complete specification. Buyers should state:
Static or kinetic COF
Film-to-film or film-to-metal measurement
Test method and conditioning time
Storage temperature
Acceptable range
Measurement direction, where relevant
The greater the resistance to sliding, the higher the COF value. Anti-block may also affect measured handling behaviour, so both functions should be assessed in the final film.
Avoid Assuming a Universal Dosage
Dosage depends on active concentration, resin, film thickness, layer design and target performance. A percentage recommended for one film should not be transferred automatically to another structure.
Trials should begin with the supplier’s guidance for the exact grade. Change one variable at a time and record extrusion conditions, roll behaviour, COF, opening force, haze, gloss, printing and sealing results.
Information to Include in an RFQ
Base polymer and grade
Film process and layer structure
Total thickness and skin-layer thickness
Target static and kinetic COF
Required opening behaviour
Time between extrusion and conversion
Printing, lamination and sealing requirements
Storage and destination climate
Required food-contact or regulatory documentation
Trial quantity and annual demand
Conclusion
Slip masterbatch controls sliding behaviour, while anti-block masterbatch helps adjacent film layers separate. Reliable packaging performance depends on balancing both effects in the actual resin, layer structure and converting process.
Corbi Polymer supplies additive masterbatches for film and other polymer-processing applications. Buyers can submit their polymer, film structure, target COF, conversion method and documentation requirements for technical review.
Contact Corbi Polymer
Tel: +98 21 22637450 | WhatsApp: +98 912 0585654 | Email: Info@onlinecorbi.com
Comments