Curing agents are typically categorized into two types: room temperature curing agents and high-temperature curing agents, based on their application method. The main difference lies in their usage scenarios. Room temperature curing agents are ideal for applications that do not require a heating process, while high-temperature curing agents, also known as blocked curing agents, can remain stable at normal temperatures. These agents can coexist with water-based resins such as aqueous polyurethane, water-based acrylate, fluorine emulsion, or silicone emulsion for extended periods. When subjected to heat treatment (above 95°C), the isocyanate (-NCO) groups within the curing agent react with functional groups like hydroxyl, carboxyl, or amino groups on the aqueous resin molecules, forming a crosslinked network. This reaction significantly enhances the performance of the aqueous resin, including improved water resistance, chemical resistance, and mechanical properties.
Unlike traditional two-component systems, blocked curing agents eliminate the need for precise mixing ratios, reducing waste and improving handling. Their versatility makes them suitable for various applications. For example, Moore Chemical’s blocked water-based isocyanate curing agent is used in multiple ways: first, as an internal crosslinking agent in one-component thermosetting water-based coatings, enhancing water resistance, chemical resistance, wear resistance, adhesion, and mechanical strength. Second, as a bridging agent for organic fluorine or silicone emulsions, it helps fix these components onto cotton or polyester fibers, boosting the wash resistance of "three-proof" fabrics. Third, it acts as a crosslinker in textile coatings and printing adhesives, improving adhesion and durability.
Fourth, it serves as an internal crosslinking agent in one-component metal or glass baking paints, replacing amino resins without releasing formaldehyde and offering excellent yellowing resistance. Fifth, it improves the bonding between polyester and rubber when used as a treatment agent for polyester or polyester cord fabric. Lastly, it functions as a curing agent for cathodic electrophoretic coatings based on hydroxy acrylic resins, enhancing overall coating adhesion. In the domestic market, there are several room temperature curing agents available, such as XR-100 from Xirun Chemical, offering good cost-performance. Imported products like those from Bayer provide high quality but come at a higher price. However, closed-type curing agents are still relatively rare in China, with limited options currently available.
It is a construction product that is made by casting concrete in a reusable mold or "formwork", then curing it in a controlled environment, transporting it to the construction site and lifting it in place ("tilting upward "). Instead, the standard concrete is poured into the form of a specific location and cured on site. Recently, expanded polystyrene has been used as the core of prefabricated wall panels. It is lightweight and has better thermal insulation properties.
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