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In this study, the thermoplastic polyurethane (TPU) composed of same type soft and hard segment while different hard segment contents was selected to prepare microcellular TPU foams, using CO2 as the physical blowing agent in a batch foaming process. The TPU with high hard segment content (i.e., 36.1 wt%) exhibited high complex viscosity, low initial CO2 content, and microcrystalline region, while the others (i.e., 32.0 and 26.1 wt%) showed opposite results. The cell structure evolution of TPU foams with the foaming temperature and the foaming time showed that the low hard segment content was benefiting for the expansion ratio, whereas the high hard segment content generated the microcrystalline region acting as the nucleating site to improve the cell density. The tensile behavior of prepared TPU foams was investigated in the cyclic tensile test. It was observed that the hysteresis and residual strain increased with the increasing hard segment content, furtherly exhibited lower value compared to TPU. Moreover, scanning electron microscopy, differential scanning calorimeter, and infrared spectra were used to reveal the microstructure after tensile test. The results indicated that the cell structures had a significant contribution to improve the elasticity, resulting from the protection of cells on the hard domains. POLYM. ENG. SCI., 58:E158–E166, 2018. © 2017 Society of Plastics Engineers

A nanocellular PEBA/MWCNT nanocomposite film was fabricated by stretching-assisted microcellular foaming for high-performance EMI shielding applications.

Thermoplastic polyurethane (TPU) has excellent extensibility, high abrasion resistance, good elastic resilience, and biocompatibility, and the fabrication of cellular TPU thin film by an environmentally friendly method is attractive in both the academic and industrial communities. In this work, by a novel constrained surface diffusion foaming method, cellular TPU thin films with thicknesses of 10−40 μm were prepared using CO 2 as the physical blowing agent for the first time. The TPU thin film was sandwiched by two polyimide (PI) films via compression molding. The PI films reduced the gas escape, which ensured the nucleated bubbles grew steadily and then produced cellular TPU thin film with special structure, i.e., the microcellular structure within the thin film and the micro/nanocellular bubbles on the surface of TPU thin film by the physical foaming for the first time. Furthermore, our morphological observations showed that the foam morphology in the cross section can be easily changed by adjusting the processing parameters. This interesting structure endowed the TPU thin film with improved elasticity and good thermal insulation performance. The hysteresis loss decreased by 21% (from 51.6 to 40.7%), and the thermal conductivity reduced by 37% (from 0.257 to 0.162 W•(m•K) −1 ).

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The way in which a perforated structure is formed has attracted much interest in the porous membrane research community. This novel structure gives materials an excellent antifouling property as well as a low operating pressure and other benefits. Unfortunately, the current membrane fabrication methods usually involve multi-step processes and the use of organic solvents or additives. Our study is the first to offer a way to prepare perforated membrane by using a physical foaming technique with CO2 as the blowing agent. We selected thermoplastic polyurethane (TPU) as the base material because it is a biocompatible elastomer with excellent tensility, high abrasion resistance, and good elastic resilience. Various processing parameters, which included the saturation pressure, the foaming temperature, and the membrane thickness, were applied to adjust the TPU membrane’s perforated morphology. We proposed a possible formation mechanism of the perforated membrane. The as-prepared TPU membrane had good mechanical properties with a tensile strength of about 5 MPa and an elongation at break above 100%. Such mechanical properties make this novel membrane usable as a self-standing filter device. In addition, its straight-through channel structure can separate particles and meet different separation requirements.

In this work, the foaming process was employed to achieve lightweight thermoplastic polyurethane materials, and then the hysteresis and residual strain of corresponding materials in the tensile process were quantitatively calculated. In order to study the deformed mechanism, the influences of cell type and skin-core structure on the tensile elasticity of thermoplastic polyurethane foam were investigated. The open-cell thermoplastic polyurethane foam exhibited much lower hysteresis and residual strain compared to thermoplastic polyurethane film without cell structure, which demonstrated that the open-cell structure benefited to the tensile elasticity. In the case of closed-cell thermoplastic polyurethane foam, it had lower hysteresis and residual strain than thermoplastic polyurethane film; however, higher value than the thermoplastic polyurethane film can be observed beyond 100% strain, resulting from the stress concentration in the skin-core structure. Consequently, the hysteresis phenomenon can be improved by adjusting the ratio of skin-core structure. Moreover, the influence of density on the elasticity of the open-cell thermoplastic polyurethane foam was also discussed in this study.