Ching-Wen Lou,Sheng Chu,Peiyao Liu,Xiaomeng Wang,Jia-Horng Lin,Ting-Ting Li
Due to its exceptional mechanical properties, polyurethane (PU) foam has found wide application in various fields. Microcellular foaming not only reduces weight but also enhances the cushioning properties of PU. However, current foaming methods have limitations in improving performance. Therefore, this study aimed to construct spring-like sandwich-structured flexible PU foam composites (SFFCs). These composites were prepared using a two-step foaming method, utilizing a precise amount of polyol and isocyanate as raw materials, at room temperature (28–35°C). In the preparation process, warp-knitted spacer fabrics (WKSFs) with spring-like structures were encapsulated in the middle layer, while the top and bottom layers consisted of PUF (flexible PU foam with different ring radius differences) formed through the foaming process of polyol and isocyanate. The study focused on investigating the influence of the ring radius difference ( r = 1, 1.5, 2) and the two-layer layout (staggered, diagonal, overlapping) of the WKSFs on the compression and cushioning properties. The experimental results revealed a significant improvement in the mechanical properties of the PU with the incorporation of WKSFs. Particularly noteworthy was the excellent cushioning performance exhibited by the two-layer WKSFs sample, RPUS-1, in the dynamic impact test. RPUS-1 absorbed 94.3% of the energy and reduced the impact value to 3921 N, which is 848 N (17.7%) lower than that of PU foam. Furthermore, even after 20 cycles of compression testing, the SFFCs retained excellent compressive properties, with the compressive stress only decreasing from 0.34 to 0.19 MPa. In conclusion, this study expands the application of PU in cushioning, demonstrating their potential in providing improved cushioning properties.
Rongli Zhu,Mingxi Linghu,Xueliang Liu,Liang Lei,Qi Yang,Pengjian Gong,Guangxian Li
Microcellular thermoplastic polyurethane (TPU) foams with dynamic covalent bonds demonstrating exceptional self-healing capabilities, coupled with precisely controlled micron-scale cellular architectures, present a promising solution for developing advanced materials that simultaneously achieve damage recovery and low density. In this study, a series of self-healable materials (named as PU-S) with high light transmittance possessing two dynamic covalent bonds (oxime bond and disulfide bond) in different ratios were fabricated by the one-pot method, and then the prepared PU-S were foamed utilizing the green and efficient supercritical carbon dioxide (scCO2) foaming technology. The PU-S foams possess multiple dynamic covalent bonds as well as porous structures, and the effect of the dynamic covalent bonds endows the materials with excellent self-healing properties and recyclability. Owing to the tailored design of dynamic covalent bonding synergies and micron-sized porous structures, PU-S5exhibits hydrophobicity (97.5° water contact angle), low temperature flexibility (Tg= −30.1 °C), high light transmission (70.6%), and light weight (density of 0.12 g/cm3) together with high expansion ratio (~10 folds) after scCO2foaming. Furthermore, PU-S5achieves damage recovery under mild thermal conditions (60 °C). Accordingly, self-healing PU-S based on multiple dynamic covalent bonds will realize a wide range of potential applications in biomedical, new energy automotive, and wearable devices.
危险品化学品经营许可证（带存储）