Surlyn Packaging Downgauging

- January 01, 2016 -

Sustainability goals set by companies and governments provide strong downgauging incentives for packaging film converters and brand owners. So reducing the carbon footprint of packaging, and reducing its total cost, are now strongly linked.

Environmental fees in Europe aimed at promoting waste reduction are one example. The trend toward higher fossil-fuel costs worldwide is another. Clearly, optimizing packaging is only going to become more important. But at the same time, consumers expect packaging to be smarter, stronger, safer, and more convenient than ever – whether it’s for food or prescription drugs.

Starting at the Shelf

Recent surveys conducted in the U.S. show that in the food and beverage sector, the most important packaging features to consumers were freshness, taste, clarity, convenience, safety, and waste reduction. In other words, people wanted packaging that used less while doing more.

Applying Material Science

DuPont™ Surlyn® presents a downgauging opportunity for the packaging industry while meeting higher expectations and reducing total costs. Super-strong Surlyn® ionomer resin comes in a range of grades that provide outstanding combination of attributes, including:

  • Stiffness
  • Formability
  • Puncture and abrasion resistance
  • Excellent sealing
  • High clarity

Delivering Results: Processed Meat Packaging

In one recent example, for packaging designed to display and maintain freshness for bacon and other processed meats, Surlyn® ionomer helps reduce costs while providing added value.

As indicated above, top and bottom web film thickness was significantly reduced by more than 30%, yet stiffness was retained. Direct raw material savings amounts to 4%.

An additional savings of 4% environmental tax fee (DSD) was also achieved for this specific film converter in its market. All while achieving overall enhanced package quality, including improved gloss and transparency, perforation resistance, faster line speed, and reduced purge, thanks to strong secondary sealing.

Delivering Results: Dry Food Packaging

In a second example, a paper-based soup sachet was redesigned to incorporate Surlyn® which allowed packaging downgauging from 120 μm to 92 μm while maintaining stiffness and actually improving sealing.

Material cost for making the packet can be reduced by up to 13% depending on the grade of Surlyn® ionomer used. Recycling fees (in this case, the German DSD fee) can decrease by up to 5%. And, despite downgauging the structure by 23%, the bending stiffness of the entire structure remains unchanged.

Downgauging and Bending Stiffness Model

DuPont integrates material and computer science in working with film converters to get stiffness right. To ensure downgauging does not compromise quality, DuPont has developed special software to model the stiffness of packaging structures containing up to nine layers. “Bending Stiffness Model” software has shown that films based on Surlyn® can be competitive with conventional films in terms of raw material cost, while maintaining overall stiffness despite considerable downgauging.

Two examples of this involve Surlyn® in dry food packaging and in processed meat packaging. Using DuPont Bending Stiffness Model software, these two typical film structures have been redesigned to develop new films with:

  • Reduced weight
  • Maintained stiffness
  • Improved seal integrity
  • Enhanced mechanical properties

Downgauging and Total Cost

To help model the total cost of the packaging operation, DuPont Packaging has developed a web-based application called SaVE (Sealant Value Estimator). SaVE integrates the cost savings derived from higher line speeds, lower number of repacks online, lower leaker rates offline, and fewer returns from retailers into the “total cost” of the packaging operation.

As one example, using these tools, and taking into account the entire process for a typical situation of vacuum-packed fresh meat, DuPont calculates an overall savings of 38% on the total cost of the packaging operation – including film, operation, and waste – versus other alternatives.

The Chemistry of Surlyn®

Surlyn® ionomers are ethylene acid copolymers that have been partially neutralized with sodium or zinc salts. Most of the mechanical properties of Surlyn® are directly related to its acid content and level of neutralization. The higher these two parameters, the stronger Surlyn® ionomers are, and the greater the potential for thickness reduction.

However a high level of neutralization can lead to products whose viscosity is not always well-suited to every extrusion process. The family of Surlyn® grades listed below covers a relatively large viscosity domain to fit most processing requirements:

  • Surlyn® 1706 (Zn ionomer, blown film application)
  • Surlyn® 1707 (Na ionomer, blown film application)
  • Surlyn® 1605 (Na ionomer, blown film, cast film, and extrusion coating applications)

These grades are approximately twice as stiff as conventional Surlyn® grades while maintaining the same extrudability and processability. Results can include:

  • Enhanced packaging solutions
  • Reduced environmental footprint
  • Differentiation in an ever-more standardized industry

DuPont collaborates with film converters worldwide to make super-strong Surlyn® an efficient choice for application-specific performance improvement while downgauging packaging and reducing costs.