This is a collaboration between the Engineering Research Center (ERC) for Advanced Engineering Fiber and Films (CAEFF) at Clemson University and Hoowaki LLC. CAEFF is a graduated, self-sustaining ERC (EEC-9731680) that continues to conduct systems-level research and educate students on advanced fibers and films. Hoowaki LLC is a small business company that has completed a Phase I SBIR (Grant No. 0945386) and developed unique expertise in surface microstructuring of metal molds. The vision of the Hoowaki-CAEFF Clemson team is to translate research and test-beds developed in CAEFF into commercial products being developed by Hoowaki LLC to radically modify surface properties of extruded polymeric articles to create large markets and to realize important societal benefits. The Hoowaki-CAEFF team proposes to develop micropaterned extrusion dies to attain micron- and submicron-level (nano-level) features on film surfaces. Hoowaki researchers have demonstrated superhydrophobic microstructures of polymers using 3-D patterns on mold surfaces used in batch processing. The proposed program will result in extruded films with desired micro-patterns and functional performance (such as superhydrophobicity) using the continuous, high-volume extrusion process, which is well suited for scale-up to commercial processes. Dies developed by Hoowaki will be used by CAEFF researchers in extrusion test-beds developed under the auspices of the ERC program. The proposal will draw upon CAEFF's custom-designed single- and multi-layer polymer film extrusion test-beds equipped with real-time Raman spectroscopy and x-ray diffraction capabilities. Extensive rheological and analytical instrumentation, also available in CAEFF, will be used for flow and microstructure measurements. CAEFF-Hoowaki team will complement these experimental studies with computer modeling using FiSim software, which was also developed under the auspices of the ERC program. Validated computer modeling predictions using accurate viscoelastic constitutive equations will systematically guide the micropatterning geometries for attaining superhydrophobic microtexture and reduced friction properties.
Broader Impact The Hoowaki R&D Manager and CAEFF Director will mentor a post-doctoral research associate and a graduate, who in turn will mentor an undergraduate student. Thus, integration of research and education will be accomplished to ensure training of research personnel for U.S. competitiveness. Hoowaki personnel will also advise post-doctoral, graduate, and undergraduate students on aspects of product-development and entrepreneurship. This work is expected to benefit society and U.S. consumers by improving packaging films to improve cleanliness for improved hygiene. The micro-patterned dies are expected to lead to improved energy efficiency of film extrusion due to improved production rates. In addition, reduction of fluoropolymer coatings, in favor of the microtexture to enhance superhydrophobicity, will provide significant environmental benefits.
This project was a collaboration between Hoowaki LLC, a small business, and Center for Advanced Engineering Fibers and Films (CAEFF), a graduated and self-sustaining NSF Engineering Research Center. The goal of this ERC-Small Business collaborative project was for CAEFF researchers to conduct an integrated experimental-modeling study on the processing of micro-textured films using innovative designs of micro-patterned dies created by Hoowaki LLC. All of the three micro-patterned dies originally proposed have been produced by Hoowaki LLC, and CAEFF researchers have successfully extruded polypropylene films using these Hoowaki dies and extrusion test-beds originally developed during the NSF-ERC program. Thus, the first major outcome of this collaborative study was that micro-textured films were produced by a scalable continuous film extrusion process, which displayed a significant reduction (up to 60%) in coefficient of friction. It is noted that polymeric melts are complex viscoelastic fluids, and the output extrudate does not conform to the shape or size of the die pattern. Therefore, to accurately predict the shape and size of the micro-textures as a function of complex die micro-patterns, finite element analysis (FEA) was successfully implemented by CAEFF researchers for modeling such viscoelastic fluids. Finite element analysis was successfully used by CAEFF researchers for modeling viscoelastic fluids. Thus, the second major outcome of the project was the modeling methodology developed that will help expedite the design of future innovative dies. Films produced by CAEFF-Hoowaki collaborative team have been submitted to numerous commercial producers of films, sheets, and tubing. These include large-volume film producers, specialty producers, and some high-performance extruded products. Specialty films and extruded products have been commercially successful, and Hoowaki LLC has already derived revenues in all of past three years. Thus, the third major outcome of this collaborative small business – ERC study has been the commercialization of extruded product forms for medical and industrial uses.