## 1 Introduction  
Microencapsulation is a kind of packaging technology that can store and protect the core material for a long time, and release the core material when needed. Self-repairing microcapsules release the core material to repair cracks when they appear [1, 2, 3]. [PERSON] et al. [4] prepared nifedipine-loaded poly(lactic acid) (PLA)/polyethylene glycol (PEG) microcapsules by solvent evaporation method, and the effects of PLA and PEG on the drug release behavior of microcapsules were studied. By analyzing and testing the microcapsules, PLA and PEG were found to react, and the safety of the drug carrier for clinical use was proved. [PERSON] et al. [5] applied the microcapsule technology to waterborne fabric coating, and studied the coating with waterproof, ultraviolet resistance, heat preservation and other multi-functions. Novel multifunctional cellulose/silica hybrid microcapsules were prepared. It was found that the microcapsules can be well scattered into waterborne coatings. The coating had superhydrophobicity, ultraviolet resistance and thermal insulation. [PERSON] et al. [6] studied the particle size of polyurea-formaldehyde microcapsules with linseed oil as the core material. The experiments showed that the stirring speed, the reaction temperature and stabilizer concentration were all factors affecting the diameter of microcapsules. The effect of microcapsules on the self-healing properties of epoxy resin coating was also studied. [PERSON] et al. [7] prepared a self-healing microcapsule which could inhibit the interfacial corrosion of the coating and was used for long-term protection of aluminum alloy. The experimental results showed that the modified intelligent epoxy coating had good resistance, active and self-repair properties, and had a certain corrosion inhibition ability. The prepared microcapsules could also improve the barrier and adhesion of the coating. In our study [8], prepared waterborne emulsion microcapsules and the various performance of microcapsules were tested. The results show that the microcapsules added to the water-based primer film had better liquid resistance, good stability and aging resistance.  
The function of paint film is to protect the surface of furniture and prevent furniture from aging or damage due to environmental and human factors [9]. If the microcrack is not repaired in time, it will affect the use of furniture and the life of furniture. The microcapsule healing method can automatically repair microcracks in the process of no artificial repair and reduce the cost of manual repair.  
Topcoat is a kind of coating on the surface of substrate. In the process of practical application, it is directly in contact with the environment and users, and will be affected by humidity, temperature, ultraviolet, human damage and other factors, so it is very easy to crack and reduce the service life of paint film on furniture surface [10; 11; 12]. Therefore, the topcoat paint film needs to have higher impact resistance, better gloss, smaller color difference and other properties. For the self-repairing coating, it also needs to have a certain crack self-healing effect [13; 14; 15; 16; 17]. The water-based acrylic acid coated with urea formaldehyde is a kind of self-healing microcapsule. The wood surface was coated by water-based topcoat paint with microcapsules that can repair the cracks [18; 19; 20].  
The self-healing water-based microcapsules were prepared with urea formaldehyde resin as wall material and Nippon water-based acrylic acid as core material. As shown in Figure 1, the microcapsules ruptured and core material flowed to the crack, where the water-based acrylic acid was crosslinked into a solid to fill the crack so as to repair the crack. By exploring the self-healing properties of microcapsules and studying the effect of microcapsules on the properties of wood surface coating, this paper provides a reference for research on preventing cracks of wood furniture surface coating.