Polymer water-based release agents, an indispensable functional material in modern concrete construction, play a crucial role in achieving efficient separation of the formwork from the concrete surface through film-forming technology. This film-forming principle is based on the physicochemical properties of polymer emulsions. Through water evaporation, particle fusion, and intermolecular forces, a uniform film is formed, thereby reducing interfacial adhesion and ensuring a smooth release process and excellent concrete surface quality.
The film-forming process of polymer water-based release agents begins with the spreading of the emulsion on the formwork surface. When the release agent is sprayed or brushed onto the formwork surface, its emulsion particles spread rapidly due to surface tension, forming a moist liquid film. In this process, the surfactants in the emulsion play a key role, reducing the liquid-solid interfacial tension and allowing the release agent to uniformly cover the formwork surface, including micropores and irregular areas. This spreadability ensures the continuity of film formation, laying the foundation for subsequent film formation.
As water evaporates, the polymer particles in the emulsion gradually approach and fuse. Under the influence of ambient temperature and airflow, the water content in the liquid film gradually decreases through evaporation, leading to an increase in the concentration of polymer particles. When the interparticle spacing decreases to a certain extent, van der Waals forces, capillary forces, and other physical forces promote particle surface contact and fusion, forming a continuous polymer network structure. This process is similar to a "particle stacking-fusion" mechanism, ultimately generating a dense and uniform film.
The stability of the film is closely related to the polymer molecular structure. Polymer water-based release agents typically use polymers with specific molecular weights as film-forming materials, and their chain length and branching degree directly affect the film's flexibility and strength. For example, polymers with linear molecular chains tend to form films with better flexibility, while polymers with higher branching degrees may enhance the film's abrasion resistance. Furthermore, the cross-linked structures that may exist in the film further enhance its heat resistance and chemical corrosion resistance through chemical bonding, ensuring that it does not decompose or detach during concrete pouring and curing.
The low surface energy characteristic of the film is key to achieving effective release. The film formed by the polymer water-based release agent has low surface energy, meaning its adhesion to the concrete surface is much weaker than the cohesion within the concrete. After concrete is poured, the film acts as an isolation layer, preventing direct contact between the concrete and the formwork, thus requiring only minimal external force to separate them during demolding. This low adhesion not only reduces demolding difficulty but also avoids surface damage to the concrete caused by forced demolding, such as porosity and pitting.
Environmental factors significantly influence the film-forming process. Conditions such as temperature, humidity, and airflow velocity indirectly affect the quality and performance of the film by regulating the rate of water evaporation and polymer particle fusion. For example, excessively rapid water evaporation at high temperatures may cause surface cracking, while high humidity conditions may prolong the film-forming time. Therefore, in practical applications, the dilution ratio of the release agent and the application process must be adjusted according to environmental conditions to ensure optimal film formation.
The film-forming principle of the polymer water-based release agent also reflects its environmental advantages. Compared to traditional oil-based release agents, water-based release agents use water as the dispersion medium, avoiding the use of organic solvents and thus reducing the emission of volatile organic compounds (VOCs). Furthermore, no harmful substances are generated during the film-forming process, making it friendly to the health of construction workers and the environment. After the film forms, unreacted polymer components can be further reduced in environmental impact through natural degradation or recycling.
The polymer water-based release agent in concrete release agents forms a uniform film through emulsion spreading, water evaporation, particle fusion, and intermolecular forces. Its low surface energy characteristics ensure effective release, while its environmental advantages meet the requirements of sustainable development in modern construction. This film-forming principle not only provides an efficient and reliable release solution for concrete engineering but also promotes the green transformation of release agent technology.
