Bag Film: Things You May Want to Know
Fueled by trust and integrity, Hangzhou Haimu Technology Co., Ltd. takes pride in contributing to a Chinese way of having developed bag film. It's not always easy, but with ingenuity and a willingness to dig down and dig in, we find ways to rise up and overcome the challenges that stand in our way to develop this product.
There is no doubt that our HARDVOGUE products have helped us to consolidate our position in the market. After we launch products, we will always improve and update the performance of the product based on the users' feedback. Thus, the products are of high quality, and customers' needs are satisfied. They have attracted more and more customers from both home and abroad. It results in growing sales volume and brings higher re-purchase rate.
Service is an essential part of our endeavor at HARDVOGUE. We facilitate a team of professional designer to work out customization plan for all products, including bag film.
When using BOPP (Biaxially Oriented Polypropylene) film for in-mold labeling (IML) in injection molding, several challenges may arise during printing, processing, and molding. Below is a detailed breakdown of common problems and corresponding solutions.
1. Printing Issues
Problems:
● Ink adhesion problems: BOPP film has a smooth, non-porous surface, making ink adhesion difficult.
● Ink drying issues: Some inks dry too slowly on BOPP, leading to smudging or incomplete curing.
● Color variation or poor opacity: The ink may not appear as expected due to the film’s transparency or reflectivity.
Solutions:
✅ Use IML-compatible inks, such as UV-curable or solvent-based inks, to improve adhesion.
✅ Perform surface treatment (e.g., corona treatment or primer coating) to increase surface tension and ink bonding.
✅ Choose white or opaque BOPP films for better color consistency and opacity.
2. Static Electricity Problems
Problems:
● Film sticking together: High static charge causes BOPP labels to stick, making feeding and handling difficult.
● Dust attraction: Static buildup attracts dust and debris, which can affect print quality and mold adhesion.
Solutions:
✅ Use anti-static treatments or coatings on the BOPP film to reduce static buildup.
✅ Install ionizing bars in the production line to neutralize static charges.
✅ Maintain proper humidity levels in the production environment to minimize static electricity.
3. Die-Cutting and Label Handling Issues
Problems:
● Poor die-cutting precision: BOPP’s toughness can cause rough or uneven cuts.
● Edge curling: Improper cutting or tension control may lead to curled labels, affecting placement in the mold.
● Film tearing or warping: Incorrect tension during processing can damage the labels.
Solutions:
✅ Use sharp, high-precision dies and optimize cutting pressure for clean edges.
✅ Control web tension in the cutting process to prevent label warping.
✅ Use multi-layer BOPP films that provide better stiffness and stability.
4. Adhesion and Bonding Problems in the Injection Mold
Problems:
● Label shifting inside the mold: If the label does not stay in place, it can cause misalignment or defects.
● Weak bonding with plastic: BOPP film may not adhere well to the injected plastic, leading to peeling.
● Wrinkling or air bubbles: Poor label positioning or excessive mold temperature can cause defects.
Solutions:
✅ Use static charge or vacuum systems to hold the label in place before injection.
✅ Ensure the film is coated with a suitable anchoring layer for better adhesion to the molded plastic.
✅ Adjust mold temperature and injection pressure to minimize air entrapment and improve label integration.
5. Temperature and Shrinkage Issues
Problems:
● Film shrinkage or distortion: High temperatures during molding can cause the BOPP label to shrink unevenly.
● Dimensional stability problems: If the film expands or contracts too much, it can lead to misalignment.
Solutions:
✅ Use high-heat-resistant BOPP films specifically designed for IML applications.
✅ Ensure proper label conditioning before molding to minimize expansion or shrinkage.
✅ Control mold temperature and injection cycle time to reduce thermal stress on the label.
6. Environmental and Storage Problems
Problems:
● Film brittleness in low temperatures: BOPP can become brittle in cold storage conditions.
● Moisture-related issues: High humidity can affect ink adhesion and cause film distortion.
Solutions:
✅ Store BOPP film in a controlled environment with stable temperature and humidity.
✅ Use protective packaging to prevent dust and moisture exposure.
✅ Allow films to acclimate to room temperature before printing and molding.
Summary Table
|
Issue Category |
Specific Problems |
Solutions |
|
Printing Issues |
Ink adhesion problems, slow drying, poor opacity |
Use IML-compatible inks, surface treatments, and opaque films |
|
Static Electricity Issues |
Labels sticking together, dust attraction |
Apply anti-static treatments, use ionizing bars, control humidity |
|
Die-Cutting Issues |
Rough cuts, edge curling, film warping |
Use sharp dies, control web tension, choose multi-layer films |
|
Molding Adhesion Issues |
Label shifting, weak bonding, wrinkles/bubbles |
Use static charge or vacuum systems, adjust mold conditions |
|
Temperature Issues |
Shrinkage, dimensional instability |
Use high-heat-resistant BOPP, control mold temperature |
|
Storage Issues |
Brittleness in cold, moisture effects |
Store in a controlled environment, acclimate before use |
Offering IML-grade BOPP films that are pre-treated for printing, anti-static properties, and high-temperature resistance will improve product performance and processing efficiency.