Xian-zhi Zhou,Cheng-cheng Zeng,Zi-jian Li,Gang Li,Sheng-jun Zheng,Fu-De Nie
Interfacial strength is a key factor affecting the mechanical properties of materials. This study aims to enhance the mechanical properties of energetic polymer bonded explosives (PBXs) by modifying 1,3,5-triamino-2,4,6-trintrobenzene (TATB) crystals—a typical energetic material—using 2-ureido-41H-6-methyl-pyrimidinone (UPy) derivatives with strong hydrogen-bonding interactions. Specifically, strongly adhesive polydopamine (PDA) was employed to graft UPy-functionalized molecules with isocyanate groups (–NCO) and hydroxyl groups (–OH). Scanning electron microscopy (SEM) images indicate that TATB crystals became rougher after being coated with PDA, while the introduction of UPy did not affect the surface morphology. The presence of urethane bond peaks in the samples indicates that UPy-NCO was successfully grafted onto the PDA. UPy is essentially nonpolar and is prone to bind with binders, having the potential to improve the creep resistance of PBXs. Due to the strong interfacial enhancement by UPy and PDA, the tensile strength and compressive strength of the sample grafted with 1 wt% UPy significantly increased by 35.6 % and 26.5 %, respectively. Theoretical calculations indicate interfacial enhancement by UPy introduction, where the strong hydrogen bonding may produce a positive impact. The successful introduction of UPy modified the nature of TATB and improved its interfacial strength, finally enhancing the mechanical properties of the PBXs. The conditions for the grafting reaction in this study are mild and universal and thus can be applied to other compositions.
Biomineral materials such as nacre of shells exhibit high mechanical strength and toughness on account of their unique “brick-mortar” multilayer structure. 2-Ureido-4[1H]-pyrimidinone (UPy) derivatives with different types of end groups, due to the self-complementary quadruple hydrogen bonds and abundant Ca2+ binding sites, can easily self-assemble into supramolecular aggregates and act as templates and skeleton in the process of inducing mineral crystallization. In this work, UPy derivatives were used as templates to induce the mineralization and growth of CaCO3 through a CO2 diffusion method. The morphology of CaCO3 crystals was modulated and analyzed by adjusting the synthesizing parameters including Ca2+ concentration, pH, and end groups. The results showed that, by the regulatory role of the mineralization template, it was easier to realize the multilayer crystal structure at a lower concentration of Ca2+ (less than 0.01 mol L–1). Under alkaline regulation, the quadruple hydrogen bonds would be destroyed, and the template’s regulation effect on the morphology of CaCO3 crystals would be weakened. Moreover, by comparing different types of end groups, it was proven that the UPy derivatives with carboxylic acid groups (−COOH) played a crucial role in the process of CaCO3 crystallization with unique morphologies.
Ji Ma,Kaili Zhang,Lili Du,Xujie Wang,Zhijie Chen,Hao Chen,Changfeng Chen,Ping Qiu
Corrosion-resistant coatings with self-healing capabilities are still a great challenge for metal protection. In this study, a corrosion-resistant coating with intrinsic self-healing capabilities was developed by compounding hydroxy-terminated silicone oil (HTSO) with 2-ureido-4[1H]-pyrimidone (UPy) derivatives. The smooth surface of the coating was shown by scanning electron microscopy (SEM), and good smoothness was also exhibited in the cross-section, which indicated that the coating is very homogeneous from the top to the bottom. Thermogravimetric analysis (TG) was employed to illustrate the temperature-resistant characteristics of the coating, revealing its significant chemical stability up to 360 °C. The corrosion resistance of the coating is assessed through electrochemical impedance spectroscopy (EIS), the typical impedance at 0.01 Hz is 1.70 × 109 and 2.44 × 108 Ω·cm2 before and after exposure to a 3.5 wt % NaCl solution for 70 days. There was no significant change in the water contact angle of the coatings before and after immersion; however, the adhesion strength was reduced. Notably, the coating demonstrates immediate and multiple self-healing properties. The tensile stress of the associated healing sample experiences an augmentation within the temperature range of 30–120 °C, with the critical fracture strain of the healed sample reaching 235% at 120 °C. The self-healing mechanism of the coating is systematically investigated using in situ Raman spectroscopy.
危险品化学品经营许可证（带存储）