Top 50

Top 50 food packagers coming in July & the Top 25 beverage packagers coming in August.
Don’t miss these exclusive issues.

Case Forming/ Packing/ Sealing / Adhesives/sealants / Snack Food Packaging / Supplier Products

Peelable sealing improves with ultrasonics

May 17, 2013
/ Print / Reprints /
ShareMore
/ Text Size+
Trans

Usually, snack packages are sealed with traditional heat sealing systems that result in peelable seals – with a common width of 15 to 24mm. The width is necessary to guarantee seal tightness and to create the opening characteristics of a peelable seal. Traditional heat seal systems are cost-effective and very common. However, extensive control samples in the Herrmann Ultrasonics (www.herrmannultrasonics.com) laboratory showed that approximately 40% of heat seals in the market are not peelable or tight. Seals created with Herrmann Ultrasonics sealing systems are tight and peelable, but the previous tool design was too narrow to offer the chips consumer the familiar peelable opening characteristics.

Sophisticated new anvil contour

The goal of Herrmann Ultrasonics was to develop a new anvil contour for a tight yet peelable ultrasonic seal, which is similar to a heat seal with respect to characteristics and visual appearance. In the ultrasonic sealing process, the packaging materials to be joined are placed between the sonotrode and the anvil. In order to focus the ultrasonic energy, small bundled contours (top, radius or plateaus which are arranged as vertical lines) in the anvil are necessary. The seal quality depends on the line height, distance, quantity and design of this contoured anvil. Therefore, the following criteria were determined in the lab, based on a DOE process:

  • Seal width
  • Distance between the sealing lines
  • Selection of the contour (plateau, radius or top)
  • Sealing force


The correct sealing force insures an even distribution of the created flow of the seal layer, with few wrinkles, which therefore provides for an even distribution of force across the length of the seal. This is critical for the peel ability of the seal.

Ideal Peel characteristics

It is easy to peel a seal if it has a cohesion fracture (separation of the seal layers of the films) resistance of 4 to 6 N/15mm over the length of the seal. It is difficult to peel seals that have an adhesive fracture resistance in the area of the seal (delamination). The chart below shows an ideal force path during a tensile test: an even increase, when an individual seal line opens, with a subsequent rapid decrease once that particular seal line is fully separated. The ‘force peaks’ are comparatively equal to each other in this multiple line seal:

The tightness of the seal was verified using the liquid Rhodamin (red dye in pure alcohol). A seal is proven tight if no dye can be seen on the other side of the bag. Also, it was verified that dye was not present between the multiple seal lines after the dye dried or the alcohol was vaporized.

Conclusion:

  • It is possible to create tight yet peelable cross seals.
  • Ultrasonic seals of metallic foils are peelable starting at widths of 7mm. Therefore, it is possible to reduce the overall amount of the packaging material. Heat seals typically have a seal width of 15 to 24mm. The percentage of the area of a typical heat seal is approximately 8% to 12% of the package. This can be reduced by 50% when sealing with ultrasonics.
  • The overlap longitudinal seal (back seal) can also be sealed with ultrasonics, offering a similar tight seal.
  • The ultrasonic tooling remains cool, which eliminates shrinking and visual changes to the foil structure. 

Did you enjoy this article? Click here to subscribe to Food and Beverage Packaging

You must login or register in order to post a comment.

Multimedia

Videos

Image Galleries

2014 Beverage Breakthroughs of the Year

Beverage packaging innovations huff, puff and blow traditional packaging down.

Food and Beverage Packaging

FBP July 2014 cover

2014 July

Check out the July 2014 issue of Food & Beverage Packaging, featuring our Top 50 Food Packagers list!

Table Of Contents Subscribe

Alcohol Packaging

What type of packaging is the next big thing for alcoholic beverages?
View Results Poll Archive

The Food and Beverage Packaging Store

M:\General Shared\__AEC Store Katie Z\AEC Store\Images\FBP\modified-atmosphere.gif
Modified Atmosphere and Active Packaging Technologies

Many factors are relevant in making the proper choice of food packaging material, including those related to shelf life and biodegradability.

More Products

FBP Buyer's Guide

2013 FBP Buyers Guide

 

 

Food and Beverage Packaging's Buyer's Guide provides a list of suppliers of food and beverage packaging solutions. 

Clear Seas Research

CS-OflRGBhomepage.jpgWith access to over one million professionals and more than 60 industry-specific publications, Clear Seas Research offers relevant insights from those who know your industry best. Let us customize a market research solution that exceeds your marketing goals.

STAY CONNECTED

 Facebook iconTwitter iconYoutube icon LinkedIn icong+icon