Waterborne coatings are becoming increasingly important in the modern coatings market due to their environmentally friendly properties and low volatile organic compound (VOC) emissions. However, compared with traditional solvent-based coatings, waterborne coatings often face challenges in terms of film-forming and adhesion. To address these issues, some functional additives are usually added to the formulation. Hydroxyethyl cellulose (HEC) is one of the widely used thickeners and functional additives, which plays an important role in improving the film-forming and adhesion of waterborne coatings.
1. Basic properties of hydroxyethyl cellulose (HEC)
HEC is a non-ionic water-soluble polymer obtained by chemical modification of natural cellulose. Its molecular structure contains a large number of hydroxyethyl groups, which makes it have good water solubility and film-forming properties. The main characteristics of HEC include:
Thickening effect: HEC can effectively increase the viscosity of waterborne coatings, giving them better rheology and stability during coating.
Film-forming property: HEC can form a uniform film during the drying process of the coating, improving the physical properties of the coating.
Compatibility: HEC has good compatibility with a variety of water-based resins and pigments, and is not prone to formula instability or stratification.
2. Mechanism of HEC in enhancing film-forming properties in water-based coatings
HEC can significantly enhance film-forming properties in water-based coatings, mainly due to its unique molecular structure and physical and chemical properties.
Physical cross-linking of molecular chains: HEC molecular chains are long and flexible. During the drying process of the coating, these molecular chains can entangle with each other to form a physical cross-linking network, increasing the mechanical strength and flexibility of the coating.
Moisture control: HEC has good water retention and can slowly release moisture during the drying process of the coating, prolonging the film-forming time, allowing the coating to be formed more evenly, and reducing cracking and shrinkage caused by too fast drying speed.
Surface tension regulation: HEC can effectively reduce the surface tension of water-based coatings, promote the wetting and spreading of coatings on the surface of the substrate, and improve the uniformity and flatness of the coating.
3. Mechanism of HEC in enhancing adhesion in water-based coatings
HEC can also significantly improve the adhesion of water-based coatings, which is mainly reflected in the following aspects:
Interface enhancement: The uniform distribution of HEC in the coating can increase the contact area between the coating and the substrate surface and enhance the interfacial bonding force. Its molecular chain can interlock with the tiny concave and convex parts of the substrate surface to improve physical adhesion.
Chemical compatibility: HEC is a non-ionic polymer with good chemical compatibility with a variety of substrates (such as metal, wood, plastic, etc.), and is not easy to cause chemical reactions or interfacial compatibility problems, thereby improving adhesion.
Plasticizing effect: HEC can play a certain plasticizing role in the drying process of the coating, making the coating more flexible, so that it can better adapt to the tiny deformation and thermal expansion and contraction of the substrate surface, and reduce the peeling and cracking of the coating.
4. Application examples and effects of HEC
In practical applications, HEC is widely used in various types of water-based coating formulations, such as water-based architectural coatings, water-based wood coatings, water-based industrial coatings, etc. By adding an appropriate amount of HEC, the construction performance of the coating and the quality of the final coating film can be significantly improved.
Water-based architectural coatings: In water-based wall paints and exterior wall paints, adding HEC can effectively improve the coating’s rolling and brushing performance, making the coating easier to apply and the coating film more uniform and smooth. At the same time, HEC’s water retention can also prevent cracks in the coating film caused by drying too quickly.
Water-based wood paint: In water-based wood paint, HEC’s thickening and film-forming properties help improve the transparency and flatness of the paint film, making the wood surface more beautiful and natural. In addition, HEC can enhance the water resistance and chemical resistance of the coating film and improve the protective effect of wood.
Water-based industrial coatings: In water-based metal coatings and anti-corrosion coatings, HEC’s adhesion enhancement allows the coating film to better adhere to the metal surface, improving anti-corrosion performance and service life.
As an important functional additive, hydroxyethyl cellulose (HEC) significantly improves the overall performance of the coating in water-based coatings by enhancing film-forming properties and adhesion. Its thickening, water retention, film-forming and interface enhancement effects enable water-based coatings to perform well in various application scenarios, thus meeting the market demand for high-performance, environmentally friendly coatings. In the future, with the continuous improvement of environmental protection and performance requirements, the application prospects of HEC in water-based coatings will be broader.