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,
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 . 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 , was revealed by Raman spectroscopy (ID/IG = 0.127) . 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 . 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 . 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.