Why Replace Petroleum Based Extrusion Coated Polyethylene?
More and more printers and converters are responding to requests for paper and paperboard coatings that can replace petroleum based extrusion coated polyethylene (PE) or Poly Replacement. Alternative barrier coating products that are safe for the environment are in favor due to brand marketers, and legislative, political, and consumer pressure.
Poly (PE) Replacement Barrier Coatings
The aim is to reduce the use of petroleum based plastics. The vast majority of polyethylene coated substrate is dumped into landfills where the paper portion degrades quickly, while the PE portion is estimated to take decades to break down. Polyethylene has dominated as a barrier coating in packaging applications because of its low cost, versatile properties, and the ease with which it processes.
Poly (PE) coated paperboard and paper are considered to be “bulletproof” by many offering an over-kill in terms of barrier performance. Therefore, these substrates are broadly accepted and are generally not subjected to barrier testing by printers or converters.
Poly Coating Pros
- Good Water Resistance
- Moderate MVTR Permeability
- Good Grease Resistance
Poly Coating Cons
- Highly Permeable to Oxygen- Gases
- A Poor Odor Barrier
Cork Industry Solves Poly Replacement
Cork Industries, long in the aqueous coating business, has developed a line of FDA direct food contact compliant barrier coatings that are providing an alternative to (PE) coated paper and paperboard. These coatings are often application specific as they can be formulated across a wide range of desired properties. Because of this, barrier performance testing has come into the picture.
Applications for barrier coatings include food bags and wraps, food trays, plates, take-out containers and cups, folding cartons and boxes, flexible packaging, and other protective packaging. Food packaging & food service products can rapidly lose their appeal to consumers if grease and oil staining, or water degrade their appearance.
Cork has developed Green Aqueous Protective Barrier Coatings with These Important Properties:
- Oil & Grease Resistant
- Liquid Water Resistant
- Low in Odor Permeability
- Recyclable and Compostable
- Biodegradable
- From Sustainable & Renewable Resources
- Direct Food Contact FDA Compliant
Other Desirable Properties of Cork’s Barrier Coatings include:
- Ease of Application
- Non-Blocking
- Flexibility
- Absence of Pinholes
- Consistent COF
- Heat Resistance
- Gloss
Water-based barrier coatings are water-based dispersions of film-forming polymer(s), additives, and possibly pigments. These barrier coatings give useful properties when applied to paper and paperboard. Paper and paperboard substrates are biodegradable and sustainable, provide mechanical strength, printability, and opacity, and are cost-effective.
Barrier Coating Properties, End Uses, and Relevant Tests
Moisture Resistance (Water or Vapor)
- Folding Cartons
- Multi-Wall Bags
- Corrugated Boxes
- Deli Containers
The most common test method is TAPPI T 441 om-98 (commonly referred to as the “Cobb Test”). In the EU, surface water absorption is measured using the Cobb test in accordance with ISO 5351. The water absorption is expressed in g/m².
Other test methods include testing with a MOCON unit or TAPPI T 448 om-09. In the EU, they may also perform a water absorption, wick test. Water absorption at the paperboard edge is measured using a Wick test. The paperboard surface is sealed with waterproof tape on both sides. The sample is weighed, placed in water at 80°C for 20 minutes, and reweighed. The amount of water absorbed by wicking is expressed in kg/m².
Oil and Grease Resistance
- Folding Cartons
- Fast Food Containers
- Meat Packaging
- Deli Containers
The most common test method is TAPPI T 559 cm-12 (commonly referred to as the “Kit Test”). Other test methods include TAPPI T 507 cm-99, and customer-specific tests.
Aroma Barrier
- Candies
- Chocolate
- Tobacco Products
- Food Products (may require an Antimicrobial Additive)
Test methods include GC-Olfactory techniques—often customer-specific.
MOCON (www.mocontesting.com) is one company that provides these services.
Chemical resistance
- Alcohol
- pH
Test methods include TAPPI T 559 cm-12 (commonly referred to as the “Kit Test”) and, typically, customer-specific tests.
Recommended Cork Aqueous Barrier Coatings
- Chemical, Grease, and Moisture Barrier tested for dryer sheet boxes.
- Poly Replacement Coating for donut and bakery boxes.
- Oil and Grease Resistant coating for French fry bags, clam shells, and pizza boxes.
Consult Cork coating expects to explore available aqueous barrier coatings designed to meet specific product application requirements, and in doing so replace (PE) coated paper & paperboard substrates.
