Thermal Conductivity of Ultrahigh Molecular Weight Polyethylene: From Fibers to Fabrics

Abstract

Unique combinations of properties such as mechanical compliance and chemical stability make polymers attractive for many applications. However, the intrinsic low thermal conductivity of bulk polymers has generally limited their potential for heat dissipation applications, and in fact they are widely used as thermal insulators. But in recent years, gel-spun, ultra-oriented fibers made of ultra-high molecular weight polyethylene (UHMW-PE) have sparked interest in the thermal management community due to their exceptionally high thermal conductivity. These fibers are typically used in commercially-produced protective gear such as motorcycle jackets and ballistic vests due to their high mechanical strength, but they have not been widely utilized for heat spreading and thermal management applications. While recent studies have characterized individual fibers and ultra-drawn films, the thermal properties of fabrics constructed from these materials remain virtually unexplored. Here, we synthesize plain-weave fabrics from yarns of commercially available gel-spun UHMW-PE and measure the thermal properties of the individual microfibers, yarns, and woven fabrics using an in-house thermal characterization technique based on infrared microscopy. For the woven fabric, we report an effective in-plane thermal conductivity of ~10 Wm-1 K-1 in the direction aligned with the weft yarns, which is 2-3 orders of magnitude higher than conventional textile materials. This work reveals the high thermal conductivity of UHMW-PE fabrics that can be realized using a scalable textile manufacturing platform and lays the foundation for exploiting their unique thermomechanical properties for heat spreading functions in flexible/wearable devices.

Thermal and mechanical characterization of high performance polymer fabrics for applications in wearable devices

“…This is observed as a relatively steeper temperature drop in the wire in the direction toward the point of contact with the sample. Additionally, a higher thermal conductivity sample will exhibit a more linear temperature profile in the sample due to heat conduction along the sample dominating compared to radiation loss to the surroundings 28 . These heat transfer mechanisms (conduction and radiation) are of comparable magnitude for a low conductivity sample leading to a non-linear decaying temperature profile.…”

“…The high-performance polymer fibers typically have ~ 1–2 orders of magnitude higher thermal conductivity and elastic modulus (note the log scales). Data compiled from references 28 , 30 – 39 with details for the high-performance fibers summarized in Table 1 . …”

“… Axial thermal conductivity (Wm −1 K −1 ) Refs. General properties Dyneema Ultra-high molecular weight polyethylene (UHMW-PE) Gel-spinning process using spinneret (super drawing, heating, elongating, and cooling) 14.2 30 High strength to weight, abrasion resistance, mechanical strength, thermal conductivity 101 30 23.6 31 113 32 28.4 28 22.5 33 Spectra Ultra-high molecular weight polyethylene (UHMW-PE) Gel-spinning process 118 30 15.8 30 High strength to weight, abrasion resistance, mechanical strength, thermal conductivity 113 32 20 34 Zylon Polybenzoxazole (PBO) Spun from Polyphosphoric acid (PPA) solutions via dry-jet wet spinning 275 30 23 30 Very high mechanical strength, excellent heat resistance; very low thermal conductivity 270 35 22.6 31 …”

“…2 b). The in-house fabricated sample (100% Dyneema) is a plain-weave Dyneema fabric constructed entirely from Dyneema SK75 microfibers (Atkins and Pearce Inc.) as described in our previous work 28 . Additionally, we acquire some conventional materials with no UHMW-PE content for benchmarking purposes: EeonTex, a non-woven fabric that is commonly used as a heater fabric in electronic textiles; a high-density polyethylene (HDPE) flexible sheet (McMaster-Carr); and a typical cotton twill weave fabric (tested for mechanical properties only).…”

“… 27 reported an in-plane thermal conductivity of ~ 4 Wm −1 K −1 for graphene woven fabric-reinforced polymer composites. Our recent work 28 showed that fabrics woven from ultra-high molecular weight polyethylene (UHMW-PE) fibers exhibit an in-plane thermal conductivity up to ~ 10 Wm −1 K –1 . More recently, Tang et al 29 constructed electronic textiles using ultrasonication of non-woven fabric in a dispersion of carbon nanotubes, and measured a thermal conductivity of ~ 3 Wm −1 K −1 .…”