44th International Conference on Environmental Systems Paper Number 13-17 July 2014, Tucson, Arizona Non-Flammable Containment Bag and Enclosure Development for International Space Station Use David P. Cadogan 1 and Sunil Inamdar 2 ILC Dover LP, One Moonwalker Rd., Frederica DE, 19946 Erica S. Worthy 3 NASA, 2101 NASA Pkwy, Houston, Texas 77058 I. Abstract Work conducted on the International Space Station (ISS) requires the use of a significant quantity of containment bags to hold specimens, equipment, waste, and other material. The bags are in many shapes and sizes, and are typically manufactured from polyethylene. The amount of bags being used on ISS has grown to the point where fire safety has become a concern because of the flammability of polyethylene. Recently, a new re-sealable bag design was developed and manufactured from a specialized, non-flammable material called ArmorFlex™ 301 specifically for this application. ArmorFlex™ 301 is also FDA compliant, clear, flexible and damage tolerant. The bags can be made with a closure mechanism similar to that of a ZipLoc ® bag or can be open top. Sample Flex- Loc™ bags were laboratory tested by NASA to verify materials properties and evaluated by astronauts on the ISS in 2012. Flex-Loc™ bag manufacturing will commence in 2014 to support a transition away from polyethylene bags used on ISS. In addition to resealable bags, other larger containment systems such as flexible gloveboxes, deployable clean rooms, and other devices manufactured from ArmorFlex™ 301 are being explored for use on ISS and in similar confined space locations where flammability is a concern. This paper will describe the development of the ArmorFlex™ 301 material, the Flex-Loc™ bag and other containment systems being explored for use in confined areas. II. Introduction iploc ® bags are one the most common used items on the International Space Station 1 (Figure 1). They are Zprimarily used for stowage, transport, and containment of a number of materials ranging from materials for experiments, to waste products. The benefits of using Ziploc ® bags include availability in many sizes, ease of opening and closing, easy of temporary stowage in ISS, optical clarity for easy recognition of contents, ease of labeling and protection of contents from external harmful agents. Ziploc ® bags also offer containment by providing some level of barrier between contents of the bag and astronauts. However, the versatility and ease of use of commercially available polyethylene Ziploc ® bags is marred by their flammability. Therefore, when used in large quantities on ISS they pose a severe fire safety risk. This risk resulted in the development of a non-flammable alternative to the Ziploc ® bags currently in use. No non-flammable bag alternative was commercially available. Several material candidates were considered for use in the construction of new resealable, non-flammable bags. The non-flammable alternative bag are needed in multiple sizes, must be easy to seal and able to maintain its seal be transparent so that items within the bag can be easily identified, be visually differentiated from the existing bags, and be compliant with NASA’s materials requirements in NHB 8060 2. Enhanced barrier properties were also desired for the new bag. 1 Director Engineering, ILC Dover LP, [email protected] 2 Lead Materials Development Engineer, ILC Dover LP, [email protected] 3 Assistant, Structural Materials, NASA, [email protected] Figure 1. Examples of the use of polyethylene storage bags on ISS. Astronaut Don Pettit’s space Zucchini – Astronaut Sandy Magnus showing citrus fruit storage - Astronauts Michael Fincke, Sandra Magnus and cosmonaut Yury Lonchakov at dinner on ISS. Images courtesy of NASA. ILC Dover was engaged by NASA to develop a new resealable, non-flammable bag because of previous experience in space suit design & manufacture, and with understanding material interface and acceptance requirements for use inside the ISS. ILC Dover has extensive experience in developing and producing thin-film containment systems and specially tailored materials for the pharmaceutical & biopharmaceutical markets. This experience was leveraged to develop several material candidates and trade them against system requirements. A new barrier film called ArmorFlex™ 301 was developed and converted into roll-goods and resealable closures that could be used in the construction of the new ISS bags. The new Flex-Loc™ bags were constructed, laboratory tested, and then evaluated on ISS. Feedback from the on orbit evaluation and the Crew Office was used for the development of an improved bag. The level of containment and protection offered by the Flex-Loc™ bags makes them ideal for confined space use such as on ISS, but also for use in submarines, biomedical research labs, aerospace applications, etc. III. New Storage Bag Requirements The operational requirements as supplied by NASA for storage bags used on ISS are listed below: • Opening and sealing: The storage bags need to be easily opened and sealed without requiring any assisting tools. The integrity of the seal should be comparable to a Ziploc ® bag. • Multiple use cycles: The bags should be reusable and should remain functional for multiple uses. • Robustness: The bags must be resistant to damage under the conditions of use on ISS. • Handling: The astronauts should be able to open and seal the bags while wearing laboratory gloves. The bags shouldn’t be too slippery to make them difficult to operate, or exhibit high levels of tack (or blocking) that would make insertion & removal of material difficult. • Sizes: 10 sizes ranging from 2 in.x2 in. up to 36 in.x36 in. and have scalable, cost-effective design. The resealable bag l is used to contain and hold tools, chemical waste, food, medicine and other waste, and must meet many requirements (Table 1). The film needs to be tough with an elongation-to-break of greater than 300% and tensile strength of greater than 3500 psi, similar to polyethylene. The bags will be used to store various chemical containers, various chemical reaction products and cleaning materials. Hence the film material needs to be chemically inert and resistant to degradation from exposure to a wide range of chemicals. To contain food and medicine, the film needs to be clean and FDA approved. To be considered a candidate, the material must meet flammability criteria in NASA-STD- 6001, Test no.1 upward flame propogation 3. Samples were tested in 24.1% oxygen which is the environment on ISS. To see and identify the items in the bag, the film needs to be optically clear or see-through clear with an acceptable level of Haze and Optical transmission. Thousands of bags are used at 2 International Conference on Environmental Systems any point in time on Space Station, and the bag material must meet an acceptable level of offgassing per NASA- STD-6001, Test no.7, which specifies toxicity limits. Material Property Requirement Tensile Modulus Equal to Polyethylene or minimum 3500 psi Elongation Equal to PE or minimum to 300% Chemical Resistance Similar to Polyethylene (resistance to physical or chemical attack of same chemical list) Food Contact Approved Yes - 21 CFR 174 - 21 CFR 190 Flammability NASA-STD-6001B, Test no.1 upward flame propagation Optical Similar to Polyethylene in transmittance and haze ASTM-D1003 Toxicity NASA-STD-6001B, Test no. 7 Table 1: Material Requirements for non-flammable bags IV. Flex-Loc™ Development The development team approached the challenge by identifying several conceptual configurations for resealable bags, and identifying or creating materials options. The concepts were then evaluated in a trade study and the leading candidates were identified. The requirements were used as the evaluation attributes in the trade studies, and each was assigned a weighting factor to emphasize the most critical needs. Once the leading candidate materials and bag configurations were identified, samples were made and testing conducted to select the final design. A. Bag Configuration Concepts The first decision point in the configuration discussion was whether to consider three-dimensional configurations (as with a paper grocery bag or a cylindrical bag with a round base. In some cases, these bag configurations can offer advantages in support during filling or handling operations. However, these characteristics are not as valuable in the microgravity environment, so only flat bags were considered. The use of tube stock was considered for the manufacture of the bags to reduce seaming (cost & risk), but since numerous sizes are required this was not economically viable. The configuration selected was two flat sheets sealed around three edges, with a closure mechanism on the opening end. Several options for closure mechanisms were considered: • Ziploc ® or similar (interfacing plastic male/female extrusions) type • Stiffener plate(s) at opening, fold and fasten with hook & loop • Stiffener plate(s) at opening, fold and fasten with resealable pressure sensitive adhesive • Stiffener plate or rod at opening, fold and fasten with a clip • Bunch, fold and lock-down with an elastic band All of the options considered could be engineered to meet most or all of the requirements. However, the zippered seal type closure was selected because of its familiarity in operation and cost advantages in production. A dual interlocking extrusion system was selected over a single interlocking extrusion for purposes of redundancy in the sealing feature. B. Material Concepts Development of