BOPP, PP, OPP, and PE films are widely used in flexible packaging, labels, and decorative applications due to their transparency, chemical resistance, and stable processing properties.

However, printing on these films isn’t always straightforward. A printed surface may look fine initially, but problems can appear during tape tests, rewinding, die-cutting, or transport. Ink may peel, scratch, or lose adhesion during these processes.

In many cases, the issue isn’t the ink itself; the condition of the film surface plays a crucial role.

Why Polyolefin Films Can Be Challenging to Print

BOPP, PP, OPP, and PE are low-polarity materials with smooth, chemically inactive surfaces. This makes it difficult for ink to wet evenly and bond strongly.

Corona treatment is commonly used to raise the surface energy and improve ink wetting. But the effect isn’t always permanent—surface tension can decline over time, and additives migrating to the surface may affect adhesion. Even with the same ink, different film batches or storage conditions can produce varying results.

Common printing issues include:

Ink removal during tape testing

Poor resistance to rubbing or scratching

Uneven ink wetting

Inconsistent adhesion across film batches

Ink peeling during die-cutting or rewinding

Reduced adhesion after storage

When these problems persist despite proper corona treatment and printing conditions, additional surface treatment may be necessary.

The Role of Print-Receptive Top Coatings

Print-receptive top coatings are applied to the film surface before printing. After drying, they form a thin intermediate layer that helps ink wet and adhere more consistently.

Unlike adding an adhesion promoter directly into the ink, a top coating modifies the film surface itself. This approach can help manufacturers maintain consistent printing performance across different ink systems and film batches.

Top coatings can improve:

• Ink wetting and spreading
• Print clarity and uniformity
• Tape-test performance
• Resistance to rubbing and scratching
• Adhesion stability during rewinding and die-cutting
• Consistency between production batches

Corona treatment and top coatings often work together: corona raises surface energy, and the coating provides a stable interface for ink adhesion.

SA-248G Water-Based Gloss Top Coating

SA-248Gis a water-based gloss top coating developed for corona-treated PE, PP, OPP, and BOPP films.

Once applied and dried, it creates a more suitable interface for UV ink, improving print adhesion and surface clarity. It’s typically used in:

• Flexible BOPP packaging films
• PP and OPP label films
• Decorative plastic films
• UV-printed packaging materials

For applications requiring a matte finish or softer touch,SA-248Mis an appropriate alternative.

Top Coating vs. Bottom Primer

Top coatings and bottom primers improve adhesion, but address different surfaces:

Top coating: applied to the printing face to improve ink adhesion.

Bottom primer: applied to the adhesive face to enhance bonding with glue or pressure-sensitive adhesive.

Identifying which surface is causing adhesion issues is critical to selecting the right treatment.

Considerations Before Production

Film type, corona level, coating weight, drying conditions, and ink system all influence results.

Before scaling production, manufacturers should evaluate:

• Tape adhesion
• Rub and scratch resistance
• Print clarity
• Performance during rewinding and die-cutting
• Stability under storage and post-processing

This ensures the selected top coating effectively addresses the adhesion challenge.

Improving Ink Adhesion Without Changing Ink

When ink adhesion issues arise, the first instinct may be to alter the ink formulation. But often, the main problem lies with the film surface.

Applying a water-based top coating provides a practical solution by preparing the film surface, rather than modifying the ink.

SA-248G is designed to enhance UV ink adhesion and provide a glossy finish on corona-treated PE, PP, OPP, and BOPP films. For matte applications,SA-248M offers an alternative.

Because printing conditions vary, testing with the actual films, inks, and equipment is recommended before full-scale production.