How to improve the barrier properties of films from a blown film line?

Enhancing the barrier properties of films produced from a blown film line is crucial in various industries, especially in packaging where product protection and shelf - life extension are of utmost importance. As a blown film line supplier, we understand the challenges faced by manufacturers in achieving high - quality barrier films. In this blog, we will explore several effective strategies to improve the barrier properties of films from a blown film line.

1. Material Selection

The choice of raw materials is the foundation for achieving good barrier properties. Different polymers offer varying levels of barrier performance against oxygen, moisture, and other gases.

Polyethylene Terephthalate (PET)

PET is well - known for its excellent oxygen and carbon dioxide barrier properties. It is widely used in the packaging of beverages, food, and pharmaceuticals. When incorporated into the film structure, PET can significantly reduce the ingress of oxygen, which is essential for preserving the freshness and quality of oxygen - sensitive products.

Polyvinylidene Chloride (PVDC)

PVDC is one of the most effective barrier polymers available. It provides outstanding barriers to oxygen, moisture, and flavors. However, due to environmental concerns and regulatory restrictions, its use has been somewhat limited in recent years. Nevertheless, in applications where high - performance barriers are required, PVDC can still be a viable option.

Ethylene Vinyl Alcohol (EVOH)

EVOH is a copolymer that offers excellent gas barrier properties, particularly against oxygen. It is highly sensitive to moisture, so it is often used in combination with other polymers that provide a moisture - resistant layer. When used in a multi - layer film structure, EVOH can effectively block the passage of oxygen, making it ideal for packaging products such as meat, cheese, and snacks.

As a blown film line supplier, we can assist our customers in selecting the most appropriate materials based on their specific requirements. Our 7/9 - layer Greentec Blown Film Line is capable of handling a wide range of polymers, allowing for the production of complex multi - layer films with enhanced barrier properties.

2. Multi - layer Film Structure Design

Designing an optimal multi - layer film structure is a key strategy for improving barrier properties. By combining different polymers with specific functions in each layer, it is possible to create a film that offers superior barrier performance compared to single - layer films.

Layer Distribution

The distribution of the barrier layers within the film structure is critical. Placing the barrier layer in the middle of the film can provide better protection, as it is shielded from direct contact with the environment. For example, in a three - layer film, a core layer of EVOH sandwiched between two layers of polyethylene can offer an excellent balance of oxygen barrier and mechanical properties.

Number of Layers

In general, increasing the number of layers can enhance the barrier properties of the film. Our 3/5 - layer Classical Extrusion Blown Film Line and 7/9 - layer Greentec Blown Film Line allow for the production of films with different layer configurations. More layers can provide multiple barriers, reducing the diffusion path of gases and moisture through the film.

3. Processing Parameters Optimization

The processing parameters during the blown film extrusion process have a significant impact on the barrier properties of the final film.

Temperature Control

Proper temperature control is crucial for ensuring the uniform melting and flow of polymers. If the temperature is too high, the polymer may degrade, leading to a reduction in barrier properties. On the other hand, if the temperature is too low, the polymer may not melt completely, resulting in poor film quality and reduced barrier performance. Our blown film lines are equipped with advanced temperature control systems to ensure precise temperature regulation throughout the extrusion process.

Blow - up Ratio

The blow - up ratio (BUR) is the ratio of the final bubble diameter to the die diameter. A higher BUR can improve the orientation of the polymer molecules, which can enhance the mechanical and barrier properties of the film. However, an excessively high BUR may cause film instability and thickness variation. Therefore, it is necessary to find the optimal BUR for each specific polymer and film structure.

Cooling Rate

The cooling rate of the blown film also affects its barrier properties. A faster cooling rate can promote the formation of a finer crystal structure in the polymer, which can improve the barrier performance. Our blown film lines are designed with efficient cooling systems to ensure rapid and uniform cooling of the film.

4. Surface Treatment

Surface treatment can be used to further improve the barrier properties of films. Plasma treatment, corona treatment, and coating are some common surface treatment methods.

Plasma Treatment

Plasma treatment can modify the surface properties of the film, increasing its surface energy and improving the adhesion of coatings or other layers. This can enhance the overall barrier performance of the film by creating a more effective barrier interface.

Corona Treatment

Corona treatment is a widely used surface treatment method that can increase the wettability and surface energy of the film. This makes it easier to apply coatings or laminates, which can improve the barrier properties of the film.

Coating

Applying a barrier coating to the film surface can provide an additional layer of protection against gases and moisture. coatings such as silicon oxide, aluminum oxide, and nanocomposite coatings can significantly enhance the barrier performance of the film.

5. Quality Control and Testing

Implementing a strict quality control and testing program is essential for ensuring the consistency and reliability of the barrier properties of the films.

In - line Monitoring

In - line monitoring systems can be used to continuously measure the thickness, density, and other properties of the film during the extrusion process. This allows for real - time adjustment of the processing parameters to ensure that the film meets the required quality standards.

Off - line Testing

Off - line testing methods such as oxygen transmission rate (OTR) testing and water vapor transmission rate (WVTR) testing can be used to accurately measure the barrier properties of the film. Regular off - line testing can help identify any issues with the film and allow for improvements to be made to the production process.

Conclusion

Improving the barrier properties of films from a blown film line requires a comprehensive approach that includes material selection, multi - layer film structure design, processing parameters optimization, surface treatment, and quality control. As a blown film line supplier, we are committed to providing our customers with the latest technologies and solutions to help them achieve high - quality barrier films.

If you are interested in improving the barrier properties of your films and want to learn more about our blown film lines, we invite you to contact us to discuss your specific requirements. Our team of experts is ready to assist you in choosing the most suitable equipment and optimizing your production process.

References

• Modern Plastics Handbook 2023 Edition
• Polymer Science and Technology: Barrier Materials - A Review, Journal of Polymer Research 2022
• Blown Film Extrusion: Principles and Practice, Second Edition by Tom I. Butler