Search

[Display omitted] • A "Plasticizing-Foaming-Reinforcing" (PFR) strategy is established to prepare PVC/polyurea blend foam. • The blend foam prepared by the PFR strategy exhibits the unique cell wall with microphase-separated structure. • PVC/polyurea blend foam shows excellent structural robustness and shape memory behavior. • The blend foam has excellent thermal insulation performance due to ultra-high expansion ratio and small cell size. Polymer rigid foams are highly required in the fields of wind power, transportation and construction due to lightweight and high performances. Herein, we have established a novel strategy of "plasticizing-foaming-reinforcing" (PFR) for preparing reprocessable thermoplastic/thermoset blend foams. PVC and the crosslinking monomers for polyurea (CMs) were melting mixed and foamed via supercritical CO 2 (sc-CO 2) foaming process followed by post-curing. The resultant PVC/polyurea blend foam presents ultra-high expansion ratio (51 times) and much smaller cell size as compared to those prepared by the traditional chemical foaming method, thus displays excellent thermal insulation performance (26.95 mW m−1 K−1) and excellent mechanical robustness, especially at lower temperature. Furthermore, the PFR strategy provides the PVC/CMs blend foam with a flexible molding ability at room temperature, allowing to form versatile three-dimensional (3D) structures. Strikingly, the microphase-separation structure of PVC-encapsulated polyurea in the cell wall endows the PVC/polyurea blend foam with excellent shape memory behavior. The PFR strategy paves a new avenue to fabricate thermoplastic/thermosetting (TP/TS) polymer blend foams in an easy-going green foaming process, which combines the performance advantages of both types of resins simultaneously possessing recyclable property. [ABSTRACT FROM AUTHOR]

[Display omitted] • Auxetic PU/PDA/GR composite foam with high EMI SE was prepared via simple method. • The relationship between EMI SE and reentrant structure was studied at first time. • The high EMI SE of auxetic foam results from the reentrant structure and high SE A. • The auxetic foam is promising as temperature-regulated EMI shielding material. In this work, two kinds of auxetic composite foams of polyurethane (PU) with polydopamine (PDA) and graphene (GR) (PU/PDA/GR) were prepared by dip-coating and ultrasonic immersing, then followed by triaxial compression-heating process. The electromagnetic interference (EMI) shielding effectiveness (SE) value of the PU/PDA/GR auxetic composite foam with a Poisson's ratio of −2.36 from PU foam with open cellular structure reaches 59.75 dB, which is 8.9 times of the positive Poisson's ratio composite foam with the same GR content. Furthermore, the relationship of the EMI shielding performance of auxetic foam with different forms of reentrant structure was studied for the first time, in which the absolute value of negative Poisson's ratio was used to quantitatively describe the difference of the reentrant structure in the obtained auxetic foam. The larger the absolute value of negative Poisson's ratio is, the better the EMI shielding performance of the composite foam is. The high absorption EMI SE and the existence of reentrant structure are the key factors for the high EMI shielding performance of the auxetic composite foam. In addition, it is found that the EMI SE of the auxetic foam can be adjusted via simple heating treatment, showing that the auxetic composite foam may be used as a temperature-regulated EMI shielding material in the future. [ABSTRACT FROM AUTHOR]