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How we’ll explain how to select the right printable Coroplast sheet and avoid ink adhesion issues before production begins.
When businesses purchase Coroplast sheets for signs, displays, election boards, advertising panels, or promotional products, price is often the first concern. However, one of the biggest problems printers encounter is poor ink adhesion.
After printing, the ink may scratch off easily, peel away, or fail the tape adhesion test. This leads to wasted materials, production delays, customer complaints, and higher costs.
The good news is that these problems are usually not caused by the printer or the UV ink. In many cases, the real issue is choosing the wrong Coroplast sheet.
Why Does Ink Fail to Stick to Coroplast Sheets?
Coroplast sheets are manufactured from polypropylene (PP), which naturally has low surface energy.
Because of this characteristic, UV ink cannot firmly bond to untreated PP surfaces.
If the sheet has not been properly treated, the ink will simply sit on the surface instead of chemically bonding with it.
Common symptoms include:
- Ink scratches off with a fingernail
- Ink peels during cutting
- Colors fade after handling
- Failed tape adhesion tests
- Poor durability during transportation
Many printing companies mistakenly replace inks or adjust printing parameters, when the real solution is selecting the correct sheet.
The Most Important Factor: Corona Treatment
The first thing professional printers should ask a supplier is:
Has the Coroplast sheet been Corona Treated?
Corona treatment increases the surface energy of polypropylene, allowing UV inks to firmly attach to the sheet.
Without corona treatment, even premium UV inks may perform poorly.
A quality Coroplast manufacturer should provide:
- Online Corona Treatment during extrusion
- Stable surface energy
- Printable surface on both sides (if required)
- Consistent treatment across every production batch
Check the Surface Tension Level
Surface energy is measured in dynes/cm.
For UV printing, recommended values are:
| Surface Energy | Printing Performance |
|---|---|
| Below 36 dynes | Poor ink adhesion |
| 38–40 dynes | Acceptable |
| 42 dynes or above | Excellent printing performance |
Professional suppliers usually perform dyne pen testing before shipment.
Always request testing reports for large orders.
Choose Virgin Polypropylene Instead of Recycled Material
Some low-cost Coroplast sheets contain a high percentage of recycled PP.
Although this reduces the price, it creates several printing problems:
- Uneven surface
- Lower corona treatment effectiveness
- Surface contamination
- Inconsistent color
- Poor ink adhesion
Virgin polypropylene provides:
- Smooth surface
- Better print quality
- Stable color
- Higher durability
- Better flatness
For advertising signs and retail displays, virgin PP is usually the better long-term investment.
Surface Smoothness Matters
Even if a sheet has excellent corona treatment, printing quality can still suffer if the surface is rough.
High-quality Coroplast sheets should have:
- Smooth finish
- Uniform wall thickness
- No surface particles
- No oil contamination
- No scratches
- Good flatness
These characteristics improve both image sharpness and ink bonding.
Match the Thickness to Your Printing Application
Different applications require different sheet thicknesses.
| Application | Recommended Thickness |
|---|---|
| Indoor signs | 2–3 mm |
| POP Displays | 3 mm |
| Yard Signs | 4 mm |
| Election Signs | 4 mm |
| Real Estate Signs | 4–5 mm |
| Heavy Duty Displays | 5–6 mm |
Selecting the correct thickness prevents bending while maintaining excellent print quality.
Color Consistency Is Essential
Many brands reorder printed signs several times each year.
If the base sheet color changes between production batches, the printed colors may also change.
Professional manufacturers use:
- Stable raw material suppliers
- Strict color control
- Batch management systems
- Consistent extrusion parameters
This ensures every order maintains the same appearance.
Ask for Adhesion Testing Before Mass Production
Before placing a large order, request sample sheets and perform several tests:
Tape Test
Apply strong adhesive tape to the printed surface and remove it quickly.
If ink peels away, the sheet may not have sufficient surface treatment.
Scratch Test
Use your fingernail or a plastic card to gently scratch the printed surface after curing.
Quality sheets should resist scratching.
Outdoor Weather Test
If products will be used outdoors, expose samples to sunlight for several weeks to evaluate color stability and adhesion.
Choose a Supplier with Printing Experience
Not every plastic sheet manufacturer understands the requirements of the printing industry.
An experienced Coroplast supplier should understand:
- UV flatbed printing
- Screen printing
- Digital printing
- Ink adhesion requirements
- Corona treatment standards
- Color consistency
- Flatness control
- Custom sheet sizes
A supplier familiar with commercial printing can help prevent costly production problems before they occur.
Questions to Ask Your Coroplast Supplier
Before purchasing, consider asking these questions:
- Is the sheet corona treated?
- What is the surface energy (dyne level)?
- Is virgin polypropylene used?
- Is both-side corona treatment available?
- Can you provide adhesion test reports?
- Is the color consistent between batches?
- What printing methods are recommended?
- Can custom sizes and colors be produced?
A professional supplier will be able to answer these questions clearly and provide supporting test data.
Why More Printing Companies Choose Xinsu
At Xinsu, we manufacture high-quality Coroplast Sheets specifically designed for printing applications.
Our advantages include:
- Premium virgin polypropylene raw materials
- Stable online corona treatment
- Excellent UV ink adhesion
- Smooth and flat surface
- Consistent color control
- Thickness from 2 mm to 12 mm
- Width up to 2600 mm
- Custom colors and sizes
- OEM manufacturing service
- Strict quality inspection before shipment
Our printable Coroplast sheets are widely used for:
- Advertising signs
- Retail displays
- Political campaign signs
- Real estate boards
- Exhibition graphics
- POP displays
- Packaging inserts
- Industrial identification panels
Whether you are a printer, distributor, or sign manufacturer, selecting the right Coroplast sheet can significantly improve printing quality while reducing waste and production costs.
Conclusion
Ink adhesion problems are rarely caused by the printer alone. In most cases, they begin with the choice of material.
When selecting a Coroplast sheet for printing, focus on more than just price. Pay attention to corona treatment, surface energy, raw material quality, flatness, color consistency, and the supplier’s printing expertise.
Investing in high-quality printable Coroplast sheets will help you achieve vibrant graphics, durable prints, and reliable production performance—ultimately saving time, reducing waste, and delivering better results to your customers.
Looking for high-performance printable Coroplast sheets? Xinsu provides factory-direct manufacturing, custom specifications, and dependable quality to support your next printing project.
