Carried within the Meal, Ready-To-Eat (MRE) packaging is the food that fuels our Nation’s military when hot, cook-prepared meals are unavailable. After MREs are consumed, however, the empty flexible packages, which make up one third of the weight of the MRE, contribute to significant waste problems for the Army in the field.

Current MRE packing accounts for more than 14,000 tons of solid waste annually, a huge logistics challenge for an Army at war. (U.S. Army NSC photo by Sarah Underhill.)

More than 14,000 tons of packaging solid waste are generated annually from the nearly 47 million operational rations consumed by Soldiers, according to a report from the DOD Combat Feeding Directorate at the U.S. Army Soldier Systems Center in Natick, MA.

Environmental research programs focusing on solid-waste reduction exist in DOD, and the Natick Soldier Center (NSC) has been instrumental in obtaining funding at the basic research to advanced technology development levels for reducing MRE packaging waste.

Research is focused on using nanotechnology to develop a new MRE packaging system consisting of nanocomposite film pouches to protect the food. Current packaging for the MRE entree consists of a retortable 4-layer pouch using aluminum foil as the barrier along with polyethylene, nylon and polyester. Other food items, such as crackers, are packaged in three-layer foil pouches. This system can only be landfilled because of the aluminum foil. The goal of the research is to remove this aluminum foil barrier layer and replace the pouch with nanocomposite films. Overall, the amount of trash generated from MREs will be reduced because the packaging will be thinner, lighter, recyclable and biodegradable.

The MRE's shelf life is 3 years at 80 degrees F and 6 months at 100 degrees F. With such stringent shelf life requirements, an exceptional barrier material is necessary for this application. The packaging also must be robust enough to withstand airdrop and rough handling associated with the military logistics system. The outer meal bag that holds all the individual components is now made from a thermoplastic polyolefin that is thick enough to resist burrowing insects. Despite these packaging precautions, MREs still suffer from flex cracking or pinholing in the foil-based laminates, especially when exposed to cold weather.

To reduce packaging without sacrificing performance, engineers at NSC are investigating various recyclable thermoplastics and biodegradable polymers blended with nanosized fillers. Nanocomposite food packaging is a potential solution for food preservation because of the high-oxygen and moisture-barrier properties of films containing nanosized platelets. With polymer nanocomposites, not only are the barrier properties improved compared to the pure or neat polymer, but the mechanical and thermal properties improve as well. This could improve structural integrity during handling at the manufacturer as well as when the MREs are exposed to cold weather during storage. If used in the outer meal bag, nanocomposites could potentially replace high barrier foil laminates. Removing the aluminum foil barrier layer dramatically improves options for disposal and recycling.

Polymeric packaging systems can also be thermoformed with a deeper configuration, enabling multiple items to be cluster-packed to eliminate redundant overwraps and paperboard cartons, thus reducing weight and volume. A research team at NSC has formulated and produced polymers with a 1-5 percent clay platelet mixture by using in-house twin-screw and blown-film extrusion equipment.

In the extrusion process, chemically treated clay platelets are mixed into the polymer to maximize clay dispersion and orientation. The surface of the clay platelets is modified for incorporation into plastic resins on a nanoscale size, 1 billionth of a meter. This is 1,000 times smaller than conventional additives or composite material fillers, such as starch.

Plastics Engineer Danielle Froio, NSC Materials Science Team, pours polymer pellets into a ThermoHaaake Twin-Screw Extruder during a production run of experimental blown-film nanocomposites. (U.S. Army NSC photo by Sarah Underhill.)

Because nanoclays contain so many individual particles in a relatively small amount of material, it takes a low percentage of clay to obtain a high concentration of constrained areas within the polymer, which lowers bulk and weight. The clay platelets disrupt the diffusion path of the oxygen and water molecules. The more tortuous the path is through the polymer chains, the better the barrier. Research has focused on materials such as polyethylene, polyester and ethylene covinyl alcohol (EVOH) nanocomposites. The low-density polyethylene (LDPE) has obtained an 80-degree-C increase in thermal stability and a 100-percent increase in Young’s Modulus (the stress of a material divided by its strain; measures the strength of the material). A biodegradable nanocomposite consisting of polylactic acid (PLA) has decreased the water vapor transmission rate by more than 50 percent compared to pure PLA while also significantly increasing mechanical properties such as toughness and modulus.

The EVOH nanocomposite achieved the oxygen barrier requirement for the MRE. However, these properties are dependent on temperature and humidity. Currently, EVOH nanocomposite layers are being sandwiched in between LDPE using a new in-house coextrusion line to make multilayer films.

Nanoclay materials in MRE production are projected to cost 10-30 percent less than current foil-based laminate materials, with a projected total life-cycle cost savings estimated at $1 million to $3 million. Nanocomposite films showing the most potential will be tested, downselected, further evaluated and compared to the existing MRE packaging to determine compliance with military requirements. The films will be further evaluated by the Advanced Processes and Packaging Team for compatibility with novel advanced food processing technologies that are incompatible with current high-barrier foil laminates.
From there, the Individual and Group Rations teams will take over on the way to manufacturing and procurement of the same warfighter-tested, warfighter-approved product with reduced packaging waste.

For more information about the U.S. Army Soldier Systems Center, go to http://www.natick.army.mil.