This Small Business Innovation Research (SBIR) Phase I project is geared toward the production of previously unprocessible polymer composite fiber materials aimed at improving performance in membrane and fuel filtering applications through environmentally friendly melt coextrusion processing of polymer fibers. This melt process strategy offers a unique opportunity to fabricate nanofibers that is typically processed by many solvent-based techniques. This proposed STTR program will demonstrate processing of novel composite, micro- and nanolayered fiber materials via a solvent-free fabrication process capable of continuous mass production and membrane formation at a potentially lower production cost than the current state-of-the art manufacturing methods. The unique ability of the polymer layering coextrusion process enables the combination of dissimilar polymer materials, creating composite multifibers of specific size and aspect ratio, hydrophobicity and hydrophilicity. Through proof-of-concept fabrication and optimization trials to melt process the polymer fibers, this project will demonstrate the ability of these materials to fill the void of easily processible, tailorable hydrophobic/hydrophilic fiber materials that are suitable for use in the $12.5 billion/year membrane market, specifically for fuel filter membranes.
The broader impact/commercial potential of this project includes initial applications in the membrane and filtration industry. Other applications expected in the field of medicine and biology are scaffolds for cell culture, tissue engineering, and drug delivery platform. Mechanically robust, highly oriented fibrous systems can also be used for clothing and packaging. Novel nanofiber fabrication approach will create a scalable process, which has a potential to create jobs in the United States. Because it is a solvent-free process, this technology is environmentally friendly and, therefore, will reduce carbon footprint and product cost. This program will also contribute to the education of engineering college students through the extensive use of co-op conducting research. The students will be hired from universities for varied duration of 4 to 12 months for this project. In addition, this STTR program also offers a unique opportunity to graduate students from area Universities to work with R&D companies and earn valuable experience. This strongly supports the NSF mission of developing the U.S. science and engineering workforce.
A novel, lower cost, more environmentally friendly manufacturing process was demonstrated to fabricate a non-woven, porous separating film for fuel filter applications at PolymerPlus and Case Western Reserve University under an NSF Phase-I STTR program, Figure 1. Through adaption of a plastics melt processing technique of multilayer coextrusion, typically utilized in the food and consumer goods packaging industry; microporous fuel filtration media films were fabricated, Figure 2, and characterized to possess similar performance (i.e. water-fuel filtration efficiency, pore size distributions, and geometric fiber sizes) as compared to a commercial composite fuel filter porous film product while demonstrating a 3X improvement in filter mechanical properties. In addition to mimicking the commercial product geometry and filtration performance, the coextrusion technique to produce filtration films is greener, i.e. requires no organic solvents during processing, and enables an increased flexibility in separation film polymer material selection/processability while maintaining a 60% lower production cost. Demonstration of the coextruded polymer film sample water –fuel separations performance was achieved in several two component polymer film systems: (1) Polyamide 6 (PA6)/ polypropylene (PP), (2) modified cellulose/PP and (3) PA6/polyvinylidene fluoride (PVDF). PA6/PP was selected as the initial model material development system for optimizing fibrous filtration media structure and filtration properties during the Phase – I program. Porous filtration samples of PA6/PP polymer fibers were coextruded and exfoliated into porous filter media film samples 1" x 1" and up to 2.5" x 2.5" in area via post extrusion uni-axial orientation and water jet exfoliation, Figure 3. The oriented fiber-film prototype filter mats exhibited up to 10X increase in surface area and up to 2X increase in porosity as compared to the commercial fuel filter media. The coextruded microporous filter fiber size distribution was comparable to a commercial melt-blown process sample and superior properties of leading wet-laid technology samples. The oriented coextruded and exfoliated films oriented possessed up to 6X the deformation strength of the commercial filters studied. Furthermore, the density and basis weight of the prototype filters was half that of the commercial fuel filters suggesting less material required for attaining filters with improved tensile strength. Preliminary filtration efficiency experiments on the coextruded and exfoliated micro-fiber filtration media 2.5" x 2.5" samples exhibited 60 to greater than 80 % separation of water from ultra-low sulfur diesel as compared to 80 % water separation using commercial filter under same testing conditions. Dust retention tests of the first generation coextruded prototypes were characterized to a 30 µm particle rating (i.e. particles > 30 µm filtered to 99% efficiency). Coextruded, porous, fuel filtration media films fabricated by PolymerPlus have demonstrated similar water-fuel filtration separation performance, pore size distributions, and fiber sizes as commercial composite fuel filter media films while demonstrating a 3X improvement in filter mechanical properties, increased flexibility in material selection/processability and the potential for a 60% reduction in existing filter media cost via a two-step, solvent free manufacturing process. A major commercial interest of the new multilayered extrusion and exfoliation filtration media processing technique is centered on the massive potential scale-up production cost savings. In contrast to existing wetlaid polyester non-woven materials that cost between $1.50 to $1.90/m2; melt processed, coextruded micro- and nano-fibers porous separation films offer a significant cost advantage due to a simpler, two step manufacturing approach that does not require additional capital investments for processing solvents or solvent recovery equipment. Manufacturing scale production, 500 lb/hr or 250,000-500,000 lb/yr, of the coextrusion and water jet exfoliation techniques developed and described in the following section of this report represent a path toward realizing coextruded porous polyester fuel filtration media films at a 60% lower price of $0.75/m2. Phase I technical and commercial development correspondence with current commercial fuel filter production companies resulted in positive feedback that a reduction in filtration media cost at this level would enable a wide adoption of the technology platform and open potential applications like water and air filtration once demonstrated in prototype and production scale fuel filtration applications.
