Floor cleaners adjust the rheological properties of solutions using thickeners. Essentially, they utilize the interaction between thickener molecules, water molecules, and surfactants to construct a viscosity system with specific shear-dependent properties, thereby optimizing the cleaner's adhesion, anti-sagging properties, and user experience. This process involves three core aspects: thickener selection, rheological type design, and synergistic matching with the cleaning system.
The mechanism of action of thickeners is based on their molecular structure characteristics. Most thickeners are hydrophilic polymers containing hydrophilic groups such as carboxyl and hydroxyl groups on their molecular chains. These groups can form hydrogen bonds or hydration layers with water molecules, and then form a three-dimensional network structure through molecular chain entanglement or cross-linking. This structure can significantly increase the viscosity of the solution while giving it non-Newtonian fluid properties—that is, viscosity changes with shear force. For example, cellulose ether thickeners maintain high viscosity under low shear conditions (such as when standing), preventing the cleaner from separating or settling; while under high shear conditions (such as during wiping), the viscosity decreases, facilitating uniform spreading of the cleaner and reducing application resistance.
Floor cleaners need to be designed with rheological types according to the usage scenario. For cleaning scenarios requiring wall adhesion (such as tiled walls), thixotropic thickeners should be selected. These thickeners form a high-viscosity gel when stationary, preventing dripping; however, when subjected to external force (such as scrubbing), the gel structure is disrupted, viscosity decreases, and the cleaner flows smoothly to cover stains. For cleaning large areas of floors, high-shear, low-viscosity properties are preferred. This means the cleaner has low viscosity and is easy to spread when applied, and its viscosity recovers rapidly after the application of external force, preventing excessive flow and uneven cleaning. Associative polyurethane thickeners are commonly used in such scenarios. Their hydrophobic groups in the molecular chain can form physical cross-links with the hydrophobic tail chains of surfactants, resulting in a rapid viscosity recovery after application and effectively inhibiting sagging.
The synergistic compatibility between the thickener and the cleaning system is crucial. The main components of floor cleaners include surfactants, solvents, and additives; the thickener must have good compatibility with these components. For example, in anionic surfactant systems, inorganic salt thickeners (such as sodium chloride) can increase solution viscosity by compressing the electric double layer of micelles, causing spherical micelles to transform into rod-shaped micelles. However, excessive sodium chloride can disrupt the electrolytic viscosity of the surfactant, leading to a decrease in viscosity. Therefore, the optimal amount of inorganic salt to add needs to be determined experimentally. For nonionic surfactant systems, water-soluble polymeric thickeners (such as polyacrylates) are often chosen. These thickeners increase viscosity through molecular chain entanglement and are unaffected by electrolytes, exhibiting superior stability.
Thickeners also improve the water retention and foam stability of cleaning agents. Water retention refers to the ability of a cleaning agent to remain on the cleaned surface. Thickeners increase solution viscosity, slowing down the rate of water evaporation, allowing sufficient time for the cleaning agent to dissolve stains. For example, in wood floor cleaners, good water retention prevents the cleaning agent from drying too quickly and causing the floor to crack. Foam stability affects the cleaning efficiency and user experience of the cleaning agent. Thickeners can form a stable foam structure, extending the foam's duration and allowing the cleaning agent to adhere to the stain surface more persistently. However, it's important to note that excessive thickening can lead to excessive foaming, negatively impacting cleaning effectiveness. Therefore, the amounts of thickener and foaming agent must be balanced.
In practical applications, the choice of thickener also needs to consider cost and environmental friendliness. Natural polymeric thickeners (such as starch and cellulose) are widely available and biodegradable, but their temperature and shear resistance are relatively poor. Synthetic polymeric thickeners (such as polyacrylates and polyurethanes) are stable, but may present biodegradation challenges. Therefore, modern floor cleaners often use a combination of natural and synthetic thickeners to balance performance and environmental friendliness. For example, in environmentally friendly wood floor cleaners, modified cellulose ethers can be combined with a small amount of associative polyurethane thickener, ensuring both adhesion and water retention while reducing environmental impact.
Thickeners in floor cleaners achieve comprehensive optimization of cleaning agent performance by adjusting the solution's rheological properties. From adhesion and anti-sagging properties to water retention and foam stability, the role of thickeners is integral to the entire cleaning process. In the future, with the development of materials science, new thickeners (such as responsive smart thickeners) will further drive the evolution of floor cleaners towards high efficiency, environmental protection, and intelligence.
