Ink Additives in Flexographic Printing: Wax, Slip, and Adhesion

Flexographic printing dominates flexible packaging — printing on polyethylene, polypropylene, PET, and aluminum foil. Each substrate demands specific performance additives.

Wax Additives (Rub Resistance)

Polyethylene wax dispersions: Most widely used; particle size 0.5–3 µm; melting point 120–140°C. Provides rub resistance without blocking.

PTFE (polytetrafluoroethylene) wax dispersions: COF as low as 0.05; used in premium applications where high gloss must be maintained.

Carnauba wax: Natural wax; high melting point (82–86°C); high gloss + rub resistance; food-contact applications.

Typical loading: 1–5% dispersion.

Slip Additives

Reduce COF of the printed surface to enable smooth passage through filling equipment.

Erucamide and behenamide: Bloom to the ink surface after cure; reduce COF from >0.5 to 0.1–0.2. Silicone additives: Very low COF (0.05–0.1); use reactive silicone types if lamination follows.

Adhesion Promoters

Untreated polyolefin films (PE, PP) have low surface energy (<36 mN/m) and poor ink adhesion.

Chlorinated polyolefins (CPO): Traditional adhesion promoter for PP. Corona/plasma treatment: Surface treatment raising energy to >44 mN/m; inks must be applied within 24–72h.

Compatibility Testing

All ink additives must pass: heat seal bond strength, tape adhesion (cross-hatch/90° peel), rub resistance (Sutherland 50–100 cycles), and COF (ASTM D1894).

HMEChem supplies wax dispersions, slip additives, and adhesion promoter concentrates for flexographic, gravure, and digital packaging inks.