Graphene nanoplatelets-based membranes for thermal comfort enhancement in textiles

L. Bonetti, A. Fiorati, A. Serafini, F. Tana, A. D’Agostino, G. Masotti, L. Draghi, R. Chiesa, S. Farè, M. Bianchi, L.G. Rizzi, L. De Nardo
Politecnico di Milano,
Italy

Keywords: graphene nanoplatelets , performance textiles, composite membranes

Summary:

Polymeric composite materials incorporating graphene nanoplatelets (GNPs) are emerging as a powerful technology to address the increasing demand for performance textiles [1,2]. Since body temperature increases under physical effort, the excessive body warming can negatively affect the comfort feeling and the physiological performances [3]. Here, we report an advanced family of nanocomposite membranes, based on a thermosetting aliphatic polyurethane resin (PU) and GNPs, for thermal comfort enhancement in functional textiles. A thorough chemico-physical characterization of GNPs was accomplished to provide an insight of the thermal properties of the produced composite materials. The highly crystallographic quality of GNPs, obtained with a proprietary patented technology [4], was revealed by Raman spectroscopy (ID/IG = 0.127) [5]. TEM and AFM analyses assessed that 90% of the analyzed GNPs possessed a thickness lower than 12 graphene planes. These results confirmed the suitability of the produced GNPs for the fabrication of membranes with superior thermal conductivity. The obtained GNPs were loaded into a PU matrix (5 and 10% w/w) by conventional industrial mixing process. The composite membranes were then characterised from a chemico-physical and thermal point of view. SEM micrographs revealed a homogenous distribution of GNPs in the PU matrix, with a preferential alignment parallel to the matrix plane. Crystalline phases present in the composites were evaluated by X-ray diffraction: two peaks around 2θ = 26.48° and 54.78°, corresponding to the characteristic peaks of GNPs, were clearly present in the diffraction patterns of PU-GNPs composites. Interestingly, the intensity of these peaks increased by increasing the GNPs loading [6]. In-plane thermal conductivity of the pristine PU membranes and PU-GNPs membranes was measured, and improved thermal conductivity (up to 471 %) was observed by increasing the percentage of GNPs. A forearm manikin device was designed and used to evaluate the thermal conductivity and thermal dissipation of the developed membranes, mimicking the possible in vivo condition [7]. PU-GNPs membranes were demonstrated to improve the thermal dissipation (Figure 1a), lowering the internal temperature of the manikin compared to pristine PU membranes (-1.2 °C for 10% GNPs-loaded membranes). Lastly, thermal images (Figure 1b) confirmed the efficacy of GNPs-loaded membranes in increasing heat dissipation. This study provides a new approach for the design of innovative membranes suitable for sport and technical textiles, with a significant improvement in the thermal comfort enhancement.