Why Thin Films Are the Most Demanding CI Flexo Substrate
Unlike paper, thin plastic films are elastic, dimensionally sensitive to temperature and tension, non-absorbent, and inherently low-energy surfaces requiring surface treatment for ink adhesion. Each film type has distinct properties that determine press setup parameters.
BOPP (Biaxially Oriented Polypropylene)
Typical thicknesses: 15–40 μm. Used for snack food bags, confectionery wrappers, tape base.
- Surface energy: 30–32 dynes/cm untreated — corona treat to minimum 38 dynes/cm for water-based inks
- Heat-sensitive due to biaxial orientation: maximum processing temperatures ~80°C
- Drying temperatures: 45–65°C inter-station (verify with specific film supplier)
- Web tension: 30–80 N/m; dyne level decays over time — verify before every run
PET (Polyethylene Terephthalate)
Typical thicknesses: 12–25 μm. Used for high-clarity pouches, pharmaceutical, laminated structures.
- Higher surface energy (40–44 dynes/cm treated) — better inherent ink adhesion than BOPP
- More dimensionally stable due to higher stiffness — supports tighter register
- Maximum drying: 60–80°C inter-station
- Web tension: 50–120 N/m; anti-static bars required (PET builds strong static charge)
PE (Polyethylene)
Typical thicknesses: 20–100 μm. Highest-volume packaging film — FFS bags, produce bags, bread bags, shrink film.
- Very low surface energy (31–33 dynes/cm LDPE) — requires strong corona or flame treatment
- Highest elasticity of common packaging films — closed-loop tension control is not optional
- LDPE maximum drying: 40–50°C; HDPE: 55–65°C
- Web tension: 20–60 N/m (extremely low for LDPE — any over-tension causes neck-in and registration errors)
Universal Best Practices
- Verify corona level before every production run — do not assume stored roll dyne levels are adequate
- Validate drying temperature profiles per substrate grade — never apply a BOPP profile to LDPE
- Install anti-static bars at infeed, between print units, and at rewind
- Use closed-loop servo tension control — manual brake adjustment is insufficient for film substrates
LISHG Master Series CI flexo presses include substrate-specific tension profiling with preset profiles configurable per substrate and gauge. Contact our application team for film-specific press setup recommendations.
