Waterproofing layers play a pivotal role in tunnel engineering and building basements. Magnesium acrylate (CA-Mg 2 ) shot-membrane waterproofing materials- commonly used as a waterproof layer- is a type of hydrogel. Poly(vinyl alcohol) (PVA) solution subjected to freezing/thawing treatment has been added to a CA-Mg 2 monomer, resulting in the formation of a CA-Mg 2 /PVA interpenetrating polymer network (IPN) hydrogel which can produced by a redox initiation system. This new IPN hydrogel contains not only a CA-Mg 2 network formed with Mg 2+ coordination bonds, but also a PVA network created by hydrogen bonding between hydroxyl groups. In comparison to CA-Mg 2 hydrogels, the fracture stress of the CA-Mg 2 /PVA hydrogel increased from 0.45 MPa to 0.72 MPa, elongation from 602% to 854%, and the self-healing efficiency of the IPN hydrogel reached 99.9% over 3 h. A new shot-membrane waterproofing materials based on the CA-Mg 2 /PVA hydrogel was prepared and its fracture stress was 1.44 MPa, and self-healing efficiency 80%, at 3 h. In addition, damage to the hydrogel could be repaired repeatedly.
Thermoset powder coatings exhibit distinctive characteristics such as remarkable hardness and exceptional resistance to corrosion. In contrast to conventional paints, powder coatings are environmentally friendly due to the absence of volatile organic compounds (VOCs). However, their irreversible cross-linking structures limit their chain segment mobility, preventing polymers from autonomously repairing cracks. Dynamic cross-linking networks have garnered attention for their remarkable self-healing capabilities, facilitated by rapid internal bond exchange. Herein, we introduce an innovative method for synthesizing thermoset epoxy containing boronic ester moieties which could prolong the life of the powder coating. The epoxy resin system relies on the incorporation of two curing agents: one featuring small-molecule diamines with boronic bonds and the other a modified polyurethane prepolymer. A state of equilibrium in mechanical properties was achieved via precise manipulation of the proportions of these agents, with the epoxy composite exhibiting a fracture stress of 67.95 MPa while maintaining a stable glass transition temperature (Tg) of 51.39 °C. This imparts remarkable self-healing ability to the coating surface, capable of returning to its original state even after undergoing 1000 cycles of rubbing (using 1200-grit abrasive paper). Furthermore, the introduction of carbon nanotube nanoparticles enabled non-contact sequential self-healing. Subsequently, we introduce this method into powder coatings of different materials. Therefore, this work provides a strategy to develop functional interior decoration and ensure its potential for broad-ranging applications, such as aerospace, transportation, and other fields.
Shuchun Gan,Bo Xu,Xiong Zhang,Jianhao Zhao,Jianhua Rong
Physically cross-linked double-network (DN) hydrogels are capturing more and more attention due to their good mechanical properties and self-recovery ability. However, they usually suffer from complicated preparation process and fussy performance regulation, which severely limit their applications in many fields. Herein, we fabricated a physically cross-linked poly(vinyl alcohol)-(2-hydroxypropyltrimethyl ammonium chloride chitosan) (PVA-HACC) DN hydrogels without organic solvents or toxic cross-linking agents via a simple two-step method of freezing/thawing and immersion processing. The effects of immersion time and concentration of Na 3 Cit solution on the structures and mechanical properties of the hydrogels were investigated. The obtained hydrogels exhibited excellent mechanical properties including high elastic modulus (1.44 MPa), high strength (a maximal tensile fracture stresses of 4.14 MPa and a maximal compressive stresses of over 70 MPa at 98% strain), and superior fracture toughness (17.09 MJ/m 3 ). In addition, good self-recovered property and anti-fatigue performance were realized for the hydrogels owing to the reversible HACC ionic networks. The preparation of PVA-HACC DN hydrogels offers a new guidance for the design and synthesis of environmentally friendly DN hydrogels with outstanding mechanical properties and broad application prospects.
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