Amod A. Ogale

Chemically oxidized pitch-based carbon fibers used as a redox flow batteries (RFBs) electrode materials proved to increase the electrochemical performance of the battery and the fibers perform on par with the commercial electrode materials.

This study explores the fabrication and mechanical characterization of biocomposite hydrogels composed of poly(vinyl alcohol) (PVA) and lignin. Two series of membranes were developed using bulk, unfractionated lignin and its low molecular weight (LMW) and high molecular weight (HMW) fractions. Membranes were cast from 5 wt % and 10 wt % PVA-DMSO solutions, incorporating lignin at concentrations of 20 wt % and 60 wt % relative to the mass of PVA. The hydrogels were formed via one or three freeze-thaw (F/T) cycles, a method known to enhance physical crosslinking, via crystallization, and improve mechanical performance. Mechanical testing was conducted to assess the influence of formulation parameters on properties such as Young’s modulus and ultimate tensile strength (UTS). In general, an increase in the number of F/T cycles resulted in stiffer hydrogels, particularly for those cast from the 5 wt% PVA-DMSO solution. Among all tested compositions, hydrogels containing LMW lignin consistently exhibited superior mechanical properties. Specifically, the highest hydrated Young’s modulus values — approximately 2 MPa and 4 MPa — were observed in 5 wt % and 10 wt % PVA-based hydrogels, respectively, both containing LMW lignin. Similarly, the highest UTS values, reaching up to 400 kPa, were measured in 10 wt % PVA hydrogels with LMW lignin, while most 5 wt % PVA membranes showed UTS values below 100 kPa. The enhanced mechanical performance of hydrogels containing LMW lignin is likely due to its improved dispersion within the PVA matrix and its greater compatibility during network formation under freeze-thaw cycling. This study demonstrates that lignin molecular weight, concentration, and the number of freeze-thaw cycles can be strategically tuned to fabricate hydrogels with a broad range of mechanical properties. This tunability enables modulus matching across a wide spectrum, offering valuable flexibility for applications in biotechnology, particularly in the design of tissue implants where mechanical compatibility with native tissue is critical.

The low-cost and sustainable non-woven carbon fibers produced from petroleum pitch using a melt-blowing process are shown to be an ideal alternative to expensive polyacrylonitrile-based carbon felt electrode material for redox flow batteries.

Corn stover-derived lignin, a sustainable and cheaper precursor, was ALPHA-fractionated and dry-spun using ethanol solvent to produce carbon fibers with improved properties via faster processing.

Metals are being replaced with high-performance and lightweight polymers, but their low thermal conductivity and poor electrostatic dissipative properties are significant problems. For the protection of sensitive electronic circuitry in automotive and aerospace parts, some device housing materials must provide electrostatic discharge and dissipate heat generated at higher rates as electronic circuits are increasingly miniaturized. Micro-texturing on the film surface can greatly enhance the heat dissipation area and was investigated in this study using low-cost graphite nanoplatelet (GNP)-filled LLDPE films. Micro-finned films (30 vol% GNP) having a 51 ± 10% larger heat-dissipation area were successfully produced using a continuous extrusion process. The through-thickness thermal conductivity of 30 vol% GNP-filled LLDPE was measured at 1.3 W/m·K, which represents a 200% improvement over that of pure LLDPE. For a GNP content of 30 vol%, the surface and volume electrical conductivity of the composite films also increased by 8 orders of magnitude (resistivity down from ≈10¹⁵ to 10⁷ Ω·cm) and electrostatic decay time reduced to a below-resolution limit of 0.01 s, at par with military standard requirements. Thus, micro-fin textured GNP-LLDPE offers a unique combination of electrical and thermal transport desired for the protection of electronic encapsulation materials.

With shrinking size of electronic devices, increasing performance and accompanying heat dissipation, there is a need for efficient removal of this heat through packaging materials. Polymer materials are attractive packaging materials given their low density and electrical insulating properties, but they lack sufficient thermal conductivity that inhibits heat transfer rate. Hexagonal boron nitride (BN) possesses excellent thermal conductivity and is also electrically insulating, therefore BN-filled polymer composites were investigated in this study. Results showed successful continuous extrusion of BN-filled linear low-density polyethylene through micro-textured dies that is a scalable manufacturing process. Through-thickness thermal conductivity measurements established that 30 vol% BN content led to an over 500% increase in thermal conductivity over that of pure polymer. Textured film surface provided about a 50% increase in surface area when compared with non-textured films. This combination of increased surface area and enhanced thermal conductivity of BN-filled textured films indicates their potential application for improved convective thermal transport.

Micro-patterned Polypropylene Films: Reduced Sliding Friction Byron Villacorta and Amod A. Ogale*, Chemical Engineering and Center for Advanced Engineering Fibers and Films (CAEFF), Clemson University, Clemson Sc 29634 Sarah Hulseman, Andrew Cannon, and Ralph Hulseman, Hoowaki LLC, 511 Westinghouse Road, Pendleton, SC 29670 *Corresponding author: Prof. Amod Ogale, ogale@clemson.edu, 864-656-5483 AbstractThere are many applications of polymeric films where low sliding friction surfaces are required,e.g., high speed packaging equipment and low-friction tape wraps. Typical methods of reducingthe apparent sliding friction of polymeric surfaces are: (a) the use of liquid lubricants such assilicone oil or erucamide, (b) powdered solid lubricants such micro-sized starch or talc and (c)fluoropolymers [1, 2, 3]. Studies on modifying the coefficient of friction (COF) by addingdifferent chemical entities have been previously reported [1, 2]. Such chemical moieties arepartially transferred from the film to other surfaces upon contact, and may contaminate thosesurfaces. Therefore, in this study, the sliding friction of micro-textured isotactic polypropylenefilms, extruded from micro-patterned dies was assessed. We investigated two micro-patternedextrusion dies, one with rectangular texture and the other with a trapezoidal one. The effect ofthe resulting film texture on the apparent film-on-film COF and film-on-metal COF wasevaluated.The films were extruded at 220°C in custom-built cast-film line consisting of a 25-mm singlescrew extruder. The ASTM D-1894 Standard Test Method for Static and Kinetic Coefficients ofFriction of Plastic Film and Sheeting (assembly C) was used for all COF measurements on 25mm wide films with the following exceptions: (a) a 19-mm stainless steel sled was used with astandard roughness of 400 grit, and (b) a cross-head speed of 50 mm/min was used to pull thesleds.For the film-on-metal tests, the kinetic COF of non-textured films was measured to be0.348±0.023. The textured films displayed a COF of 0.234±0.013 and 0.218±0.011 for therectangular and trapezoidal textures, respectively. Thus, a reduction in COF of about 35% wasobserved in textured films as compared to the non-textured films. For film-on-film experiments,the non-textured films possessed a kinetic COF of 0.186±0.013. The films obtained from therectangular patterned-die possessed a COF of 0.163±.012, and showed a reduction in COF ofabout 12% in the machine direction. Films obtained from the trapezoidal patterned-die displayeda greater reduction of 28% (COF = 0.134±.012). On the other hand, the COF of the combinationof non-textured films on rectangular textured films (COF = 0.113±0.004) in the machinedirection configuration had a more significant reduction in friction of about 40%. These resultsindicate that micro-textured polypropylene films might be effectively used in potentialapplications where low-sliding and clean surfaces are required.Acknowledgment: This work was primarily supported by National Science Foundation under AwardEEC‐1128481 and made use of ERC Shared Facilities supported by the National Science Foundationunder Award Number EEC-9731680 References 1. Zhang, Z-Z.; Xue, Q-J.; Liu, W-M.; Shen, W-C; Friction and Wear Behaviors of Several Polymers Under Oil-Lubricated Conditions. J. Appl. Polym. Sci., 1998, 68, 2175–2182. 2. Samyn, P.; Tuzolana, T.M.; Effect of test scale on the friction properties of pure and internal-lubricated cast polyamides at running-in. Polym. Text., 2007, 26, 660-675. 3. Kawaguchi, M.;Yagi, K.; Kato, T.; An effect of dewetting of lubricated surfaces on friction and wear properties. J. Appl. Phys., 2005, 97, 10P311.