BOPP Film Printing: Everything You Need to Know About Surface Treatment & Ink Adhesion

Have you ever wondered why some printed BOPP film packaging looks crystal clear and vibrant, while others scratch, peel, or look dull after just a few weeks? The secret lies in one critical step: surface treatment.

BOPP (Biaxially Oriented Polypropylene) film is naturally non-polar and hydrophobic. Its surface energy hovers around 29–31 dynes/cm — far below the 38–42 dynes/cm typically required for proper ink adhesion. This means that without treatment, most printing inks simply will not stick.

In this comprehensive guide, we break down everything packaging buyers and converters need to know about BOPP film printability — from corona treatment basics to troubleshooting common ink adhesion problems.

Why BOPP Film Needs Surface Treatment

Polypropylene in its natural state has an extremely low surface energy. Think of it like trying to write on wax paper with a ballpoint pen — the ink beads up and refuses to bond. The same principle applies to BOPP film.

Surface treatment modifies the top molecular layer of the film, introducing polar functional groups (mainly hydroxyl, carbonyl, and carboxyl groups) that dramatically increase surface energy and improve wettability.

The Three Main Surface Treatment Methods

1. Corona Discharge Treatment (Most Common)

Corona treatment is the industry standard for BOPP film. The process works by passing the film between a grounded roller and a high-voltage electrode. The electrical discharge in the air gap creates an ozone-rich plasma that bombards the film surface, oxidizing it and raising surface energy.

Key Parameters:

Typical power: 1–5 kW per meter of width

Treatment speed: 100–400 m/min

Target dyne level: 38–48 dynes/cm for solvent-based inks; 42–52 dynes/cm for water-based and UV inks

Treatment decay: Surface energy gradually declines over 3–6 months post-treatment

Pro Tip: Always measure dyne levels before printing — especially on film that has been in storage. Inline corona treaters can "refresh" aged film just before the printing station.

2. Flame Treatment

Flame treatment uses a precisely controlled gas flame to oxidize the film surface. It produces more stable treatment results than corona and achieves higher dyne levels (up to 62 dynes/cm). However, it is less common due to higher operating costs and safety considerations.

Flame treatment is preferred for:

Films requiring extremely high dyne levels

Metallized BOPP films where corona may cause pin-holing

Applications demanding long treatment shelf life

3. Plasma Treatment (Advanced)

Atmospheric plasma treatment is the newest technology. It uses ionized gas (argon, helium, or nitrogen) to functionalize the surface. Plasma treatment offers:

The highest dyne levels (up to 72 dynes/cm)

Minimal thermal impact on the film

Environmentally friendly — no solvents or chemicals

Plasma is still niche but growing in high-value applications like medical packaging and electronics.

Ink Adhesion: What Matters Most

Ink Selection by Printing Method

Common Ink Adhesion Problems & Solutions

Problem 1: Ink Rubs Off Easily (Scotch Tape Test Failure)

Cause: Insufficient surface treatment or aged film

Solution: Re-check dyne level; refresh with inline corona; consider switching to a primer-coated film

Problem 2: Mottled or Uneven Print

Cause: Uneven corona treatment across the web width

Solution: Clean or replace corona electrodes; inspect dielectric roller for damage

Problem 3: Ink Adhesion Good But Fades Over Time

Cause: Ink-film incompatibility or insufficient curing

Solution: Verify ink system matches BOPP substrate; ensure proper UV dose or drying temperature

Problem 4: Back-Side Treatment (Reverse Side Treated)

Cause: Corona discharge treating both sides instead of just the print side

Solution: Check grounding and electrode gap; use back-side treatment shielding

Best Practices for BOPP Film Printing

1. Measure dyne level on delivery. Don't assume treated film arrives at the specified level. Use dyne pens or solutions to verify.

2. Store treated film properly. Keep rolls wrapped in original packaging in a cool, dry environment (15–25°C, 40–60% RH). Heat and humidity accelerate treatment decay.

3. Use inline corona treatment. For critical jobs or aged film, an inline corona treater just before the first print station provides insurance.

4. Match ink system to substrate. Not all inks work with all BOPP grades. Work with your ink supplier to validate the system for your specific film.

5. Test before full production. Always run a small trial with the actual film lot, ink batch, and press settings before committing to a full production run.

Surface treatment is not an afterthought — it is the foundation of successful BOPP film printing. Whether you are printing flexible packaging, labels, or overwrap, investing time in understanding and verifying surface treatment will save you from costly reprints, customer returns, and brand reputation damage.

Need a reliable BOPP film supplier with consistent surface treatment quality? Shandong Shunzhan delivers corona-treated films with stable dyne levels and proven printability across flexo, gravure, and digital printing methods. Our product portfolio includes soft touch film, anti-fingerprint film, scratch-resistant film, biodegradable film, anti-fog film, matte film, and decorative film — serving packaging, labeling, printing, and lamination industries worldwide.

With advanced production lines, rigorous quality control, and a dedicated R&D team, we deliver customized BOPP film solutions that meet the specific requirements of international buyers.