New barrier plastic packaging materials advancing rapidly
By Don Rosato

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Note: This is the second article of a four-part series covering barrier packaging (1) trends, (2) material advances, (3) process technologies and (4) applications.

INDUSTRY PULSE

What is an important barrier packaging material trend?
  • 1. EVOH (ethylene vinyl alcohol) use
  • 2. Vacuum coating aluminum oxide or silicon oxide
  • 3. Compostable multilayer food packaging
  • 4. O2Block oxygen scavenging

It is important for food packaging to provide good protection against factors crucial to product quality to ensure product shelf life. Depending on product sensitivity, it is vital to provide food packaging protection with proper barrier components. For example, some products are susceptible to moisture, oxygen or both, or to other gases. Barrier films often consist of multilayers or coated films designed to be impervious to gas and moisture migration, as single-layer films are in general quite permeable to most gases. Commonly used layered barrier film materials include:
  • PP (polypropylene): Mechanical properties and water vapor barrier
  • PE (polyethylene): Sealing/water vapor barrier
  • mLLDPE (metallocene catalyzed linear low density polyethylene): Good optical and mechanical properties
  • Polyamide (nylon): Aroma/O2 barrier with stiffness
  • EVOH (ethylene vinyl alcohol): High O2 barrier — provides excellent barrier properties to gas and water vapor. It is also environmentally friendly and clear. However it is not suitable for high-temperature processes.
  • EVA (ethylene vinyl acetate): Good for sealing
  • PLA (polylactic acid): Biodegradability

Water and oxygen barrier plastic comparisons.

Various approaches can be taken to improve barrier properties in the plastics packaging sector:
  • Barrier layers can be applied onto plastic using vacuum coating (i.e. aluminum or transparent oxides such as aluminum oxide or silicon oxide applied to PET—polyethylene terephthalate, or BOPP—biaxially oriented polypropylene films).
  • Multiple-layer structures can be used.
  • Nanoparticles can be compounded into the polymer matrix to form a nanocomposite that inhibits gas permeability.
A new completely compostable multilayer food packaging barrier film has been developed by BASF. The technologies include film resins, inks, adhesives and primers and meet food packaging barrier requirements. Fully compostable, the new packaging material can go to industrial composting facilities instead of landfill.

Traditional multilayer packaging films are neither recyclable nor compostable. They are comprised of multiple layers of traditional plastics and adhesives needed to provide the barriers, colorful print and necessary adhesives that bond all the layers together. These various materials are not easily separated for disposal, making recycling problematic, and the chemicals those layers are made from cannot be composted.


Compostable multilayer barrier film (top) and its application (bottom).

BASF's compostable packaging material consists of a six-layer film:
  • Ecoflex and ecovio (compostable polyester film)
  • Joncryl SLX (printing ink layer)
  • Epotal P 100 ECO (adhesive coating)
  • Metallization layer
  • Versamid (premetal primer)
  • Ecoflex and Ecovio (compostable polyester film)
The innovative design of the packaging and its materials allows for the entire structure to be composted.

Continuing, the first use of O2Block in EVOH (ethylene vinyl alcohol) as a composite barrier material is now available as Soarnol NC7003. Nippon Gohsei has a global licensing agreement with NanoBioMatters for exclusive use of the O2Block barrier additive in EVOH composites. The O2Block imparts improved O2 barrier properties over conventional EVOH, especially at high humidities.

NanoBioMatters and Nippon Gohsei jointly developed the O2Block barrier-enhanced EVOH in a two-year development program to significantly enhance barrier properties of Soarnol EVOH while minimally impacting processing, optical performance and cost. Using O2Block, EVOH barrier performance can be doubled even at 90 percent relative humidity by adding 4 percent O2Block within a 5 micron Soarnol EVOH layer.

The O2Block developed by NanoBioMatters Industries S.L. is an oxygen-scavenging additive for polymer-based materials. The proprietary technology is based on surface-modified phyllosilicate clay functionalized with active iron. The purified and modified layered clay is used as a performance-enhancing carrier of the oxygen-scavenging iron. The resulting material is a naturally sourced and highly efficient oxygen-scavenging product designed to provide maximum shelf life in barrier packaging. There are strong synergies between the two materials.

O2Block oxygen-scavenging technology.

Enhanced O2Block barrier properties (right) vs. no barrier (left) and standard barrier (center).

Active iron linked to the clay surface provides a uniform distribution of the active element within the additive. In addition, the iron deposited on the clay prevents platelet agglomeration, which combined with unique surface modification ensures global additive dispersion. The additive, primarily designed for plastic packaging applications, can be dispersed in almost any polymer system. All the components in the O2Block additives are considered by the FDA to be "generally recognized as safe" (GRAS).

Compared to other systems, the effective dispersion maximizes access to the active iron, ensuring minimum reaction time and uniform protection of the packaged goods. O2Block also enhances ultraviolet barrier properties, providing additional protection to packaged food. O2Block is available as a micronized powder or masterbatch.

Dr. Donald V. "Don" Rosato serves as president of PlastiSource, Inc. a prototype manufacturing, technology development and marketing advisory firm located in Concord, Mass., and is the author of the Vol 1 & 2 "Plastics Technology Handbook".