Development of Highly Transparent Organic-Inorganic Hybrid Near-Infrared Absorbing Polyethylene Film Prepared by Melt-Kneading Method

In recent years, growing concerns about global warming have heightened expectations for the development of SDG-related technologies that contribute to energy conservation and thermal management. Among these, heat-shielding films that transmit visible light while blocking near-infrared (NIR) light have attracted considerable attention. This paper reports on the development of a highly transparent heat-shielding polyethylene (PE) film fabricated by the melt-kneading method, aimed at reducing temperature increase inside agricultural vinyl greenhouses. When cesium-doped tungsten oxide (CsWO) was pulverized and surface-hydrophobized in toluene using various modified polymethyl methacrylates (PMMAs) possessing tertiary amino and hydroxyl groups and a number-average degree of polymerization of approximately 50 as polymeric dispersants, a CsWO nanoparticle dispersion (CsWO-s) coated with the dispersant was obtained. The crystallite size of the CsWO-s particles was approximately 20-30 nm. When CsWO-s nanoparticles were heated with maleic acid anhydride-modified PE (MA-PE) in toluene, highly transparent hybrid films were obtained in which CsWO-s was nano-dispersed within the MA-PE and PE/MA-PE matrices. Furthermore, when the dried CsWO-s powder was melt-kneaded with MA-PE at 160℃ and 150 rpm using a twin-screw extruder, CsWO-s nanoparticles were nano-dispersed within MA-PE to form MA-PE/CsWO-s strands. When the MA-PE/CsWO-s strands were melt-kneaded with polyethylene (PE) at 160℃ and 50 rpm using a twin-screw extruder, highly transparent PE/MA-PE/CsWO-s hybrid films were obtained. FT-IR analysis indicated that approximately 39% of maleic acid anhydride groups reacted with hydroxyl groups on the CsWO surface during the melt-kneading process, suggesting that the CsWO-s nanoparticles were densely coated with polyethylene chains. The best dispersion and highest NIR-shielding performance were achieved when poly (methyl methacrylate) modified with 2-dimethylaminoethyl methacrylate-modified (5mol%), which can interact with hydroxyl groups on the CsWO surface through acid-base interactions, was used as the polymeric dispersant. The resulting PE/MA-PE/CsWO-s hybrid film containing 1.0 wt% of CsWO exhibited excellent visible-light transmittance (>85% at 500nm) and excellent NIR-shielding performance(<52% transmittance at 1000nm).