Sulfonated-Recycled-PEEK as Matrix of Water Vapor Adsorbent SAPO-34 Based Composite Coatings for Adsorption Heat Pumps: Mechanical and Thermochemical Characterization

In this work, a composite adsorbent coating constituted by high SAPO 34 content and a sulfonated recycled poly (ether ether ketone) was investigated for adsorption heat pump technology. Specifically, the effect of polymer recycling on mechanical and thermal properties, as well as on water vapor adsorption and desorption performance, has been investigated. The degree of sulfonation obtained after 48 h of reaction remained approximately unaltered. The degradation of the polymer due to recycling anticipates the degradation of the C-C bonds of the polymer by about 20 °C without affecting the temperature at which the sulfonic groups degrade. From the mechanical point of view, the coating containing 90% zeolite, due to the use of recycled PEEK, evidenced a worsening of only 11.8% in scratch resistance compared to the virgin one, whereas the adhesive strength exhibited an increase of about 23.2% due to better miscibility of the sulfonated recycled polymer. Adsorption/desorption isobars show an almost similar adsorption capacity of the coating produced with recycled polymer compared to the virgin one, confirming that the water vapor diffusion is not hindered by the polymer matrix during the adsorption/desorption process.