Multifunctional eco-friendly water-based acrylic coatings with sustained-release of α-pinene essential oil

Objective With the enhancement of environmental protection and health awareness, the development of multifunctional eco-friendly coatings to improve indoor environmental quality and meet health-preserving needs has become a key direction for value-added innovation in the coating industry. Although traditional waterborne acrylic coatings offer environmental advantages, they exhibited significant limitations in functional expansion. While α-pinene had the potential to release plant essential oils, its excessive volatility restricted application efficacy, and existing slow-release technologies struggle to effectively enhance its long-acting performance. In response, this study employed microencapsulation technology to prepare α-pinene microcapsules using sodium alginate and TiO₂ as wall materials, aiming to expand the functionality of waterborne acrylic coatings and develop multifunctional eco-friendly coatings for improving indoor environmental quality.

Method The Pickering emulsion templating method and interfacial polymerization were used to prepare α-pinene microcapsules with sodium alginate and TiO₂ as wall materials and α-pinene as the core material. These microcapsules were incorporated into waterborne acrylic coatings to develop a new type of eco-friendly coating with both plant essential oil slow-release and photocatalytic properties. SEM, FTIR, photoelectric analyzers, and other techniques were systematically applied to characterize the properties of microcapsules and modified coatings, as well as the slow-release effect of essential oils.

Result (1) The prepared α-pinene microcapsules exhibited stable structure, good dispersibility, and excellent slow-release performance. The essential oil retention rate reached as high as 84.5% after 8 d of static storage, which was significantly higher than that of α-pinene (15.5%). This indicated that the α-pinene microcapsules effectively extended the release cycle. (2) Coatings with 6% microcapsule doping showed superior tensile strength and toughness, meeting diverse application requirements. 8% doping improved the hydrophobicity of modified paint films. The doping of α-pinene microcapsules increased coating viscosity to a maximum of 89.85 mPa·s with good leveling properties, and the paint film transitioned from transparent to translucent, preserving the natural texture of wood while providing protection. The ultraviolet absorbance of 10% doped paint film increased by approximately 6.1%, enhancing light aging resistance of the panel to some extent. (3) Both α-pinene microcapsules and modified coatings demonstrated stable photocatalytic performance. The modified coating achieved a maximum photocurrent of 2.5 μA/cm² under light irradiation, with good catalytic activity, capable of improving indoor air quality. (4) The modified coating films exhibited a matte finish, high surface hardness, and strong substrate adaptability, suitable for common substrates such as pine, white oak, and particleboard. Different substrates had minimal impact on other surface properties of paint film, indicating broad application prospects in indoor decoration and furniture coating fields.

Conclusion This study focuses on microcapsule preparation and modified coating development, effectively addressing the issues of excessive α-pinene volatility and single-functionality of traditional coatings. It achieves multifunctional integration of coatings, including slow-release of plant essential oils and photocatalytic air purification, significantly enhancing comprehensive coating performance. The developed coatings demonstrate advantages in improving indoor environments and promoting health.