The antiblocking effect

Have you done your paperwork lately? And was it hard to get all your documents into your sheet protectors because the two plastic films seemed to be stuck together? Well, then you used sleeves that do not use our antiblocking solutions.

Blocking describes the adherence of two adjacent film layers, caused by adhesion forces and electrostatic charging. It’s not only a challenge for people doing their paperwork, but for the producers of plastic films too.

Plastic films are extremely even. So, when two even plastic films touch each other, the contact surface is huge. And so are the so-called van der Waals forces between the molecules.

To overcome this “stickiness” you need to reduce the contact surface. That’s why film producers incorporate silica in their products. The tiny silica particles cause a kind of “goose bumps” under the surface of the film. These microscopic bumps act like spacers that hold the two layers apart to reduce the adhesion forces. The result: You – or your production machine – can separate the films conveniently.

If you also want to know how to overcome production problems due to electrostatic charging, we recommend our article about the antistatic effect.

Evonik is the only global producer offering both precipitated and fumed silica as antiblocking agents for polymer film production. Our SIPERNAT® portfolio has been established in the film industry for decades. It includes antiblocking agents for use in blown and cast films, including PE, PP, PET, PA, and PVC.

Our latest innovation to the antiblocking market is our SPHERILEX® agents. With their virtually round shape they can be dispensed precisely. And with their exact diameters they ensure perfect spacing properties.

Both products, SIPERNAT® and SPHERIPLEX® can easily be added during the melting process: Usually, an addition of less than 1% is sufficient to achieve a broad range of advantages:

• Exact adjustment of the antiblocking effect with a superior coefficient of friction
• Smooth film winding operations
• Improved handling properties during subsequent processing steps
• Increased productivity in film processing
• Less production downtime due to torn material
• Better storage stability
• Convenient use for your customers
• Favorable processibility through easy dispersibility in the polymer matrix
• High masterbatch loading capacity

But how does the addition of silica affect the performance of your product? Virtually not at all:

• Our antiblocking agents have little to no effect on other major film characteristics like gloss or mechanical properties.
• The refractive index of our granules is close to the refractive index of plastic polymers so that they are nearly invisible within a transparent polymer film.
• All our products provide excellent compatibility with other film additives, like processing stabilizers, UV stabilizers, and especially slip agents.

Finally, the recommended shelf life of our silica products is 24 months so that you can easily stock up to always be prepared.

Decades of experience prove: Our antiblocking agents have little to no effect on other major film characteristics like gloss or mechanical quality.

Add some green aspects to your film production: The use of our antiblocking agents reduces refuse all along the life cycle of a plastic film product.

• Production: Foils with antiblocking properties are easier to handle, so that less waste due to processing problems is created.
• Storage: Silica-treated plastic films can be stored longer, so less products have to be dumped due to decay.
• Post-production: When polymer films have a convenient adhesion, less material will be dumped because of usage problems.

Another green aspect is: Our silica agents have enormous effects on the processability and use of your products – but they have little to no effects on people and the environment: Silica is safe. That’s why they are proven suitable for use in food, feed, and in pharmaceuticals. The safety of silica as a food additive is, for example, confirmed by The European Food Safety Authority. Additionally, our silica agents received an OMRI Listed® Certification. Which means, that they are approved for the use in organic farming. Please find more points on the safety of silica in our FAQs page.

Simply send your area of interest to ask-se@evonik.com. Your message will be forwarded to one of our film experts and they will get back to you as soon as possible.

If you are already our client, you will get assistance from your regional contact and their team. We are looking forward to hearing from you!