SITIS Topic Details |
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| Proposals Accepted: | |
| Program: | SBIR |
| Topic Number: | A10-162 (Army) |
| Title: | High Barrier Packaging Based on Melt Extrudable Liquid Crystal Polymers | Research & Technical Areas: | Materials/Processes |
| Acquisition Program: | Office of the Principal Assistant for Acquisition | Objective: | Develop high barrier food packaging materials for the military using liquid crystal polymers (LCPs) that are melt processable into either cast flat film, blown films or sheets. These materials and structures should take advantage of LCP gas barrier and mechanical properties and overcome processing limitations currently observed in LCP conversion technology.
| Description: | Modern operational requirements demand state-of-the-art, high quality combat rations that provide for the nutritional needs of the Warfighter in extremely intense and highly mobile combat situations as well as other contingency operations. Consequently, combat ration packaging must maintain performance and shelf life in humid to dry conditions and at temperatures ranging from arctic to desert (e.g., -20 degrees F to 120 degrees F) environments. Ration packaging must withstand various levels of rough handling abuse during transportation, distribution, and storage. Currently, primary flexible ration packaging is based on laminated foil technology in order to provide the necessary gas barrier properties to meet the military shelf life requirement of three years at 80 degrees F and six months at 100 degrees F. For example, the maximum allowable oxygen permeation rate for the current retort pouch of the Meal, Ready-to-Eat™ (MRE™) is 0.06cc/meter squared-day-atm at 50% relative humidty (RH) and the maximum allowable water vapor permeation rate is 0.01g/meter squared-day-atm at 90% RH. Current aluminum foil-based systems are prone to pin-holing and stress cracking, and can negatively impact heating uniformity during the use of novel food sterilization techniques including pressure-assisted thermal sterilization (PATS) and microwave sterilization.The development of an innovative process that has the capability to produce a single- or multi-component packaging film and/or sheet structure based on high-performing Liquid Crystal Polymers (LCPs) will enable the production of materials with high barrier to oxygen and water vapor that is independent of environmental conditions. LCP films/sheet must also have the capability to withstand microwave sterilization and temperatures up to 135 degrees C, which will allow for high-temperature applications such as retort processing currently used for MRE™ entrees as well as Unitized Group Ration (UGR) lids and thermoformed trays.1 Based on an annual MRE™ demand of 3 million cases, elimination of the foil laminated structure in the food pouches will provide an annual cost savings of $1M to $3M which includes savings from reduced packaging material costs and the reduction in lot discards.
Despite their excellent gas barrier and mechanical properties, LCPs have been known to present a processing difficulty when working in the area of melt-extruded films. Further, there is a lack of data and experience in the industry about LCP film extrusion. Proven processing limitations have included high processing temperatures combined with difficult adhesion to substrates, thickness variations, surface finish, and non-isotropic mechanical properties as the result of uni-axial orientation of polymer chains in these materials.2 Bi-axial orientation of these polymers has been obtained through a patented rotating blown film extrusion die that overcomes the structural limitations of conventionally extruded LCP; through speed variation of the shaft and cylinder of the subject die, as well as flow rate, and temperature to affect the degree of orientation imparted to the ordered polymer feedstock.3 Additional orientation is imparted to the extruded film by virtue of the blowing processes, both following the extrusion and as a part of the heat treatment. Blends of LCPs with more processable materials such as polyolefins has shown promise and has been reported throughout the literature.4,5,6 The development of advanced, next-generation LCP films with high temperature stability, low water uptake, excellent adhesion to metals, exceptional electrical properties, and low permeability to oxygen and water vapor will provide new opportunities for food packaging. 7 The development of novel processing methods and materials for LCP films will lead to optimized film production, lower production costs, and more accurate process control.
| PHASE I: Research, develop, and design an innovative Liquid Crystal Polymer (LCP) concept and processing method, and quantify arguments to determine technical feasibility. Comparisons should be made to existing barrier packaging technology, as well as to other similar applications. Cost, processability, and functionality are important characteristics that should be featured in the design. With regard to cost, the goal is to reduce the retort food pouch price by 10-20%. Although LCPs cost more than most polymers, the advantage is that only a very thin core layer of LCP is needed for barrier properties in a multilayer polymeric film. The cost would be less since there would be a reduction in the number of polymeric layers in comparison to the existing 4 layer foil pouch which also undergoes a lamination production step. There is also life cycle cost savings assuming the performance is better with less pin-holing and stress cracks than the current foil food pouch.
Demonstrate the feasibility and practicality of this process for producing film and/or sheet structures, and provide an initial analysis of the film products to include oxygen and water vapor barrier properties and mechanical properties. The barrier data must be performed according to American Standards for Testing Materials (ASTM) methods: ASTM D3985 - Standard Test Method for Oxygen gas transmission rate through plastic film and sheeting using a coulometric sensor and ASTM E96/E 96M-05 Standard Test Methods for water vapor transmission of materials. Sheet structures must be evaluated for their ability to be thermoformed into single-cavity tray configurations. Deliver a final report specifying full-scale performance for Phase II, conceptual design, performance modeling, safety factors, risk mitigation measures, MANPRINT considerations, and estimated production costs.
| PHASE II: Optimize and refine the novel processing concept and method. Develop and produce a Liquid Crystal Polymer (LCP)-based prototype film and/or sheet structure to demonstrate technical capability that meets all temperature, barrier property, and mechanical property requirements. In addition, this system should be sufficiently mature for technical and operational testing, limited field-testing, demonstration, and display. Define manufacturability issues related to full-scale production of the prototype system for military and commercial application. Identify and address safety and human factors associated with the production and use of the prototype.
The following metrics will be used to judge success of the technology as a pouch structure: oxygen transmission rate less than 0.06 cc/m2-day,water vapor transmission rate less than 0.01 g/m2-day, low concentration within the pouch(>90% at 20cc or less), maintain pouch integrity with >90% of the pouches exhibiting no rupture or seal separation greater than 1/16 of an inch, and integrity of the pouch after environmental handling with <15% failure rate for defects at inspection.
Required Phase II deliverables include: the processing methodology to produce melt-blown and/or flat polymeric films and/or sheet for high barrier packaging applications, prototypes based on such melt-extrudable LCPs that meet or surpass the following specifications, as applicable:
(1) MIL-PRF-44073 Performance Specification - Packaging of Food in Flexible Pouches; or (2) MIL-PRF-32004B Performance Specification - Packaging of Food in Polymeric Trays. Performance for barrier, thermal and mechanical properties will be compared to the current technology controls.
| PHASE III: Upon successful completion of Phase II, the Phase III transition process will include the delivery of cost effective high barrier military food packaging structure(s) to U.S. Army Natick Soldier Research, Development and Engineering Center (NSRDEC), Combat Feeding Directorate (CFD) and other appropriate U.S. Army customers for evaluation. The new packaging structure(s) must be developed from the melt processing of Liquid Crystal Polymers (LCPs). The items must have performance properties that meet or surpass all current U.S. Army specifications for performance ((MIL-PEF-44073F or MIL-PRF-32004B, as applicable.).
Use of this advanced LCP technology will provide new and expanded opportunities for food packaging, aerospace, and medical products applications. The use of a fully-polymeric, LCP-based packaging structure will benefit all users by reducing package defects, costs, and weight. Further, this technology may be used with recently Food and Drug Administration (FDA)-accepted and/or novel sterilization methods such as pressure-assisted thermal sterilization (PATS) and microwave sterilization. Potential non-food packaging related applications include electronics in space; high performance fibers; medical tubings, hybrid fuel vehicles; cookware; and microelectronics.
| References: | 1. Website: http://www.efunda.com, Engineering Fundamentals, Polymer Materials Properties Database. 2. Lusignea, R. 2004. Orientation of LCP Blown Film with Rotating Dies. Polymer Engineering and Science, 39 (12): 2326-2334. 3. Harvey et. al, Foster Miller Incorporated, “Biaxially Oriented Ordered Polymer Films” United States Patent # 4,963,428 (1990). 4. Narh, K.A. Liquid Crystalline Polymer Blends as a Route to Self-Reinforcing Nanocomposites. Journal of Reinforced Plastics and Composites, 28, (16):1957-1963 (2009) 5. Magagnini, P.L., Paci, M., La Mantia, F.P., Valenza, A. A Study of Polycarbonate-Liquid Crystal Polymer Blends, Polymer International, 28, (4), 271-275 (2007) 6. Roy, S., Sahoo, N.G., Mukherjee, M., Das, C.K., Chan, S.H., Li, L. Improvement of Properties of Polyetherimide/Liquid Crystalline Polymer Blends in the Presence of Functionalize Carbon Nanotubes, Journal of Nanoscience and Nanotechnology, 9, (3):1928-1934 (2009) 7. Anonymous, 2002. Liquid Crystal Polymers and Packaging. Semiconductor International, (7), Reed Elsevier Inc. 8. Website: http://medical design.com/mag/composites_liquidcrystal_polymers_0908/, Composites and Liquid Crystal Polymers Work Where Others Cannot, Sep 1, 2008 |
| Keywords: | Liquid crystal polymer, melt processing, barrier properties, food packaging |
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