RESUMO
Corrosion inhibitor additives are considered to be one of the effective methods to slow down the corrosion of metals, but the corrosion inhibitors will decompose and lose their effect in a long-term corrosive environment. In this work, a smart corrosion inhibitor carrier 2-mercaptobenzimidazole-Zn2+-polydopamine@graphite (MZPG) with excellent pH response was designed and synthesized using a one-pot method. This corrosion inhibitor carrier not only has a very high 2-mercaptobenzimidazole (MBI) loading capacity (38.0%) but also maintains a very low MBI activity to inhibit the decomposition of MZPG in the environment as much as possible. The MZPG/epoxy (MZPG/EP) coatings prepared by the spraying method showed excellent mechanical properties. Electrochemical and salt spray tests showed that the MZPG/EP coatings (1.20 × 1010 Ω·cm2) have excellent corrosion resistance with Rp values up to 3 orders of magnitude higher than that of the EP coating (1.25 × 107 Ω·cm2). Notably, the MZPG/EP coatings maintained good corrosion resistance under acidic conditions due to the pH-responsive release of corrosion inhibitors. This is of great significance for the future development of coatings for highly corrosive environments.
RESUMO
Next-generation wearable electromagnetic interference (EMI) materials need to be provided with oxidation resistance, lightness, and flexibility. In this study, a high-performance EMI film with synergistic enhancement of Zn2+@Ti3C2T x MXene/cellulose nanofibers (CNF) was found. The unique Zn@Ti3C2T x MXene/CNF heterogeneous interface facilitates the loss of interface polarization, making the total electromagnetic shielding effectiveness (EMI SET) and shielding effectiveness per unit thickness (SE/d) of the films reach 60.3 dB and 5025 dB mm-1, respectively, in the X-band at the thickness of 12 µm ± 2 µm, significantly exceeding that of other MXene-based shielding materials. In addition, the coefficient of absorption gradually increases with the increasing CNF content. Moreover, under the synergistic effect of Zn2+, the film shows excellent oxidation resistance (maintaining stable performance after 30 days), greatly exceeding the previous test cycle. Furthermore, the mechanical performance and flexibility of the film are greatly enhanced (tensile strength at 60 MPa, and maintaining stable performance after 100 times bending tests) due to the CNF and hot-pressing process. Therefore, with the enhancement of the EMI performance, high flexibility and oxidation resistance under high temperature and high humidity conditions, the as-prepared films have wide practical significance and broad application prospects in a series of complex applications, such as flexible wearable fields, ocean engineering fields and high-power device packaging fields.
RESUMO
Self-healable polyurethanes can be used in various fields for extended service life and reduced maintenance costs. It is generally believed that the shape memory effect is helpful for achieving a high healing efficiency. The morphological features were focused on in this study as microphase separation is one of the main factors affecting various performances of polyurethanes, including their shape memory behavior and mechanical properties. Microphase separation can be regulated by changing the content and types of the hard segments. With this in mind, polyurethanes from polycaprolactone diol, hexamethylene diisocyanate, and different chain extenders were synthesized, characterized, and designed as promising self-healing polymers. All the polyurethane specimens were equipped with a similar content of hard segments but diverse types, such as aliphatic, aromatic, and disulfide-bonded. Differential scanning calorimetry, thermogravimetric analysis, X-ray diffractometry, infrared spectroscopy, and atomic force microscopy were used to describe the microstructures of the polyurethanes, including the crystalline regions. The relationship between the microphase separation structures and material properties was focused on in this examination. Various properties, including the thermal stability, mechanical behavior, hydrophobicity, and self-healing efficiency showed significant differences due to the change in the hard segments' structure and multiphase distribution. The aliphatic disulfide stimulated the conformation of a proper microphase separation structure (the large heterogeneous structure at physical length scales as well as a more sufficient combination of soft and hard phases), which helped to improve the healing effect as much as possible by effective wound closure and the exchange reactions of disulfide bonds.
