Substrate Protection with Corrosion Scales: Can We Depend on Iron Carbonate?

Satisfactory Tensile Strength and Strain of Recyclable Polyurethane with a Trimaleimide Structure for Thermal Self-Healing and Anticorrosive Coatings

Bismaleimide (BMI) is often used as the cross-linking reagent in Diels-Alder (D-A)-type intrinsic self-healing materials (DISMs) to promote the connectivity of damaged surfaces based on reversible D-A bond formation on the molecular scale. Until now, although DISMs have exhibited great potential in the applications of various sensors, electronic skin, and artificial muscles, it is still difficult to prepare DISMs with satisfactory self-healing abilities and high tensile strengths and strains at the same time, thus largely limiting their applications in self-healing anticorrosive coatings. Herein, symmetrical trimaleimide (TMI) was successfully synthesized, and trimaleimide-structured D-A self-healing polyurethane (TMI-DA-PU) was prepared via the reversible D-A reaction (cycloaddition of furan and maleimide). As a DISM, TMI-DA-PU exhibits apparently higher self-healing efficiency (98.7%), tensile strength (25.4 MPa), and strain (1378%) compared to bismaleimide-structured D-A self-healing polyurethane (BMI-DA-PU) (self-healing efficiency, 90.2%; tensile strength, 19.3 MPa; strain, 1174%). In addition, TMI-DA-PU shows a high recycling efficiency (>95%) after 4 cycles of recycling. A series of characterizations indicate that TMI provides more monoene rings as the self-healing sites, forms denser cross-linked structures compared to BMI, and is, thus, more appropriate to be used for DISM applications. Moreover, the barrier abilities of coatings can be semi-quantitatively expressed by the impedance value at 0.01 Hz (|Z|0.01 Hz). The |Z|0.01 Hz value of the TMI-DA-PU coating is 3.93 × 109 Ω cm2 on day 0, which is significantly higher than that of the BMI-DA-PU coating (6.76 × 108 Ω cm2 on day 0), indicating that the denser rigid cross-linked structure of TMI results in the small porosity in the TMI-DA-PU coating, thus effectively improving the anticorrosion performance. The construction of DISMs with the structure of TMI demonstrates immense potential in self-healing anticorrosive coatings.

Formation mechanisms and supervisory prediction of scaling in water supply pipelines: A review

The scaling problem in the water supply pipeline will increase the resistance coefficient of the pipeline and the pressure of the water supply pipeline, which will not only affect the operation safety of the water supply pipeline, but also cause energy waste. The scale in the pipeline will also enrich heavy metal ions and pathogenic microorganisms, affecting the safety of water supply water quality and causing secondary pollution of water quality. At present, a lot of research has been done on the composition structure and crystallization process of the scale. The study found that calcite is the main component of the scale; the scale process is a heterogeneous nucleation process induced by heavy metal particles and their corrosion products in the pipeline. The introduction of electrochemical detection technology, density functional theory and molecular dynamics simulation has greatly improved the accuracy and timeliness of water scaling conditions detection and realized the visualization of scaling mechanism. In this paper, the measurement methods of the scale in the water supply pipeline and the corresponding material composition and crystal structure characteristics are reviewed, and the mechanism of the scale and the water quality conditions are summarized. At the end of this paper, based on summarizing the existing water quality scaling tendency evaluation methods, it is proposed to establish a water quality potential scaling risk assessment framework based on Puckorius scaling index (PSI) and electrochemical impedance spectroscopy (EIS) in the future.

Synthesis of Trivinylisooctyl POSS and Its Application in UV-Curing of Polyurethane Acrylate Coatings

To improve the overall performance of polyurethane acrylic (PUAs) coatings applied to an iron or wood substrate, a modifier, trivinylisooctyl polyhedral oligomeric silsesquioxane (TVi7iso–POSS), was successfully synthesized by a polycondensation reaction in the presence of an organotin catalyst. TVi7iso–POSS is a POSS derivative possessing three olefin and seven isooctyl bonds; its molecular structure was confirmed by FT-IR, 1H-NMR, and mass spectrometry. The synthesized TVi7iso–POSS was then used as a modifier with butyl methacrylate (BMA), dodecafluoroheptyl methacrylate (DFMA), difunctional PUA (PUA–2), and photo-initiator 1173 to produce a novel polyurethane coating (PFMPUAs) via UV-curing. The performance of the obtained PFMPUAs coating was analyzed via X-ray photoelectron spectrometry, SEM, atomic force microscopy, TGA, and differential scanning calorimetry. The newly synthesized modifier, TVi7iso–POSS, enhanced the thermal stability, hardness, flexibility, impact resistance, and adhesion of the PUAs coating and maintained its good light transmittance. Moreover, the PFMPUAs coating exhibited better overall performance compared to the previously studied PUAs coating when the addition of TVi7iso–POSS and DFMA was 15 wt.% of PUA–2. Therefore, the PFMPUAs coating has potential applications in the field of environmentally friendly coatings.