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oai:uvadoc.uva.es:10324/592472023-04-21T19:00:20Zcom_10324_1158com_10324_931com_10324_894col_10324_1242

Santiago Calvo, Mercerdes Naji, Haneen Bernardo García, Victoria Martín de León, Judit Saiani, Alberto Villafañe González, Fernando Rodríguez Pérez, Miguel Ángel 2023-04-21T11:56:58Z 2023-04-21T11:56:58Z 2021 Polymers, 2021, vol. 13, n. 18, 3143 https://uvadoc.uva.es/handle/10324/59247 10.3390/polym13183143 3143 18 Polymers 13 2073-4360 A series of thermoplastic polyurethanes (TPUs) with different amounts of hard segments (HS) (40, 50 and 60 wt.%) are synthesized by a pre-polymer method. These synthesized TPUs are characterized by Shore hardness, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD), dynamic mechanical thermal analysis (DMTA), and rheology. Then, these materials are foamed by a one-step gas dissolution foaming process and the processing window that allows producing homogeneous foams is analyzed. The effect of foaming temperature from 140 to 180 °C on the cellular structure and on density is evaluated, fixing a saturation pressure of 20 MPa and a saturation time of 1 h. Among the TPUs studied, only that with 50 wt.% HS allows obtaining a stable foam, whose better features are reached after foaming at 170 °C. Finally, the foaming of TPU with 50 wt.% HS is optimized by varying the saturation pressure from 10 to 25 MPa at 170 °C. The optimum saturation and foaming conditions are 25 MPa and 170 °C for 1 h, which gives foams with the lowest relative density of 0.74, the smallest average cell size of 4 μm, and the higher cell nucleation density of 8.0 × 109 nuclei/cm3. As a final conclusion of this investigation, the TPU with 50 wt.% HS is the only one that can be foamed under the saturation and foaming conditions used in this study. TPU foams containing 50 wt.% HS with a cell size below 15 microns and porosity of 1.4–18.6% can be obtained using foaming temperatures from 140 to 180 °C, saturation pressure of 20 MPa, and saturation time of 1 h. Varying the saturation pressure from 10 to 25 MPa and fixing the foaming temperature of 170 °C and saturation pressure of 1 h results in TPU foams with a cell size of below 37 microns and porosity of 1.7–21.2% eng info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/4.0/ © 2021 The Authors Atribución 4.0 Internacional Cromatografía Calorímetros y Calorimetría Analysis of the foaming window for thermoplastic polyurethane with different hard segment contents info:eu-repo/semantics/article