Corona treatment is a crucial process in the production and application of BOPP (Biaxially Oriented Polypropylene) film. As a BOPP film supplier, I am well - versed in the ins and outs of this treatment, and I'm excited to share in - depth knowledge about it with you.
What is Corona Treatment?
Corona treatment is a surface modification technique that uses a high - voltage electrical discharge to change the surface properties of a material. In the context of BOPP film, it is used to increase the surface energy of the film. The basic principle behind corona treatment is to create a corona discharge between two electrodes. When the BOPP film passes through this discharge area, the high - energy electrons and ions in the corona plasma interact with the film's surface. This interaction causes a series of physical and chemical changes on the film surface.
Physically, the high - energy particles can etch the surface of the BOPP film, making it slightly rougher. Chemically, they can break the chemical bonds on the film surface and introduce polar functional groups such as carbonyl, carboxyl, and hydroxyl groups. These changes increase the surface energy of the BOPP film, which is essential for many subsequent processes.
Why is Corona Treatment Necessary for BOPP Film?
Printing
One of the most important applications of BOPP film is in the printing industry. For inks to adhere properly to the film surface, the surface energy of the film must be high enough. Untreated BOPP film has a relatively low surface energy, typically around 29 - 31 dynes/cm. Most inks require a surface energy of at least 38 - 42 dynes/cm to adhere well. Corona treatment can raise the surface energy of BOPP film to meet these requirements, ensuring that the printed images are sharp, durable, and do not peel off easily.
Lamination
In lamination processes, where BOPP film is bonded to other materials such as paper, cardboard, or another layer of film, good adhesion is crucial. The increased surface energy provided by corona treatment improves the wetting and bonding properties of the film. This results in a strong and reliable laminate, reducing the risk of delamination during handling, storage, or use.
Coating
BOPP film is often coated with various substances such as adhesives, anti - static agents, or barrier coatings. Similar to printing and lamination, these coatings need to adhere firmly to the film surface. Corona treatment enhances the surface's receptivity to coatings, allowing for a more uniform and durable coating application.
The Corona Treatment Process for BOPP Film
Equipment
The corona treatment equipment typically consists of a power supply, electrodes, and a treatment station. The power supply generates a high - voltage, high - frequency electrical current. The electrodes are usually made of metal and are arranged in a way that creates a corona discharge zone. The BOPP film is passed through this zone at a controlled speed.
Parameters
Several parameters need to be carefully controlled during the corona treatment process. The power level of the corona treatment unit is one of the most important factors. Higher power levels generally result in a greater increase in surface energy, but excessive power can damage the film. The speed at which the film passes through the treatment zone also affects the treatment effect. A slower speed allows for more exposure to the corona discharge, leading to a higher surface energy increase. Additionally, the distance between the electrodes and the film surface, as well as the ambient conditions such as temperature and humidity, can influence the treatment outcome.
Quality Control of Corona - Treated BOPP Film
Surface Energy Measurement
To ensure that the corona treatment has been effective, the surface energy of the BOPP film needs to be measured. One common method is the dyne test. Special dyne solutions with different surface tensions are applied to the film surface. If the solution spreads evenly on the film, it indicates that the surface energy of the film is at least equal to the surface tension of the solution. Another method is contact angle measurement. A small drop of liquid is placed on the film surface, and the angle between the liquid - film interface and the liquid - air interface is measured. A lower contact angle indicates a higher surface energy.
Aging of Surface Energy
It's important to note that the surface energy of corona - treated BOPP film may decrease over time. This is known as surface energy aging. The rate of aging depends on several factors, including the type of film, the storage conditions, and the extent of the initial treatment. To minimize aging, the film should be stored in a cool, dry place, and subsequent processing steps should be carried out as soon as possible after corona treatment.
Our BOPP Film Products and Corona Treatment
As a BOPP film supplier, we offer a wide range of BOPP film products, including Super / Crystal Clear BOPP Film Jumbo Roll and Normal BOPP Film Jumbo Roll. All of our films undergo a precise corona treatment process to ensure optimal surface properties for various applications.
Our Super / Crystal Clear BOPP Film Jumbo Roll is known for its excellent clarity and high gloss, making it ideal for high - end printing and packaging applications. The corona treatment on this film is carefully calibrated to provide the perfect surface energy for top - quality printing results.
Our Normal BOPP Film Jumbo Roll, on the other hand, is a more cost - effective option for general - purpose applications. Despite its lower cost, we still apply high - standard corona treatment to ensure good adhesion in printing, lamination, and coating processes.
Conclusion
Corona treatment is an indispensable process in the production and application of BOPP film. It significantly enhances the surface properties of the film, enabling it to be used in a wide range of industries such as printing, packaging, and lamination. As a BOPP film supplier, we are committed to providing high - quality corona - treated BOPP films that meet the diverse needs of our customers.
If you are interested in our BOPP film products or have any questions about corona treatment, we encourage you to contact us for procurement and further discussion. We look forward to working with you to find the best BOPP film solutions for your specific requirements.
References
- ASTM D2578 - 14(2020). Standard Test Method for Wetting Tension of Polyethylene and Polypropylene Films.
- Pritchard, G. (Ed.). (2008). Plastics Materials. Butterworth - Heinemann.
- Wypych, G. (2012). Handbook of Polypropylene and Polypropylene Composites. William Andrew.
