In this paper, photochromic and thermochromic microcapsules were selected. There are three different coating processes: “the primer with the photochromic microcapsules, the topcoat with the thermochromic microcapsules”, “the primer with the thermochromic microcapsules, the topcoat with the photochromic microcapsules”, and “the photochromic and thermochromic microcapsules added into the primer and topcoats” to explore the color-changing effect of the coating on the surface of basswood (Tilia) and the comprehensive properties of the paint film. The optical properties, mechanical properties, cold liquid resistance, and aging resistance of the coating were mainly analyzed. It was concluded that the comprehensive performance of the coating was the best when thermochromic and photochromic microcapsules were mixed on the surface of basswood (Tilia). At a temperature of 80 °C, the color difference reached a maximum of 20.2, and the coating was completely discolored. The color difference of the coating after discoloration under visible light illumination was 56.9. The gloss under the angle of incidence at 60° was 37.4, hardness was 3H, adhesion grade was 1, impact resistance was 10.0 kg·cm, and cold liquid resistance grade was 1. The method of mixing the two microcapsules had better aging resistance. In this paper, the photochromic and thermochromic properties of the coating were studied, and the optimal discoloration of the surface coating of the basswood substrate was solved by different coating processes. This study provided a method for a coating to achieve both photochromic and thermochromic discoloration, broadening the application of discoloration coatings.Keywords:coating process;discoloration;microcapsules;paint film performance
Lacquer is the main raw material of lacquerware, while UV-irradiation is an important factor leading to its aging. In order to investigate the aging behavior of urushi lacquer film under UV-irradiation, and to propose parameters that can be used to evaluate its aging degree, the micro-UV/Py-GC/MS system has been applied in the present work to enrich and identify volatile products released by urushi film during aging on the one hand, and to investigate micro-amount and conventional urushi films with different aging degrees on the other hand, in addition, representative historical samples have also been investigated. Volatile products released by urushi film demonstrate that during UV-irradiation, polysaccharides wrapping urushiol polymer would be first degraded to generate furans and alcohols, and then urushiol polymer would undergo photo-oxidation and break of molecular chain, mainly generating oxidation products including aldehydes, organic acids, and ketones, as well as a small number of alkyl benzenes and hydrocarbons. Py-GC/MS analysis of micro-amount urushi films with different aging degrees indicates that UV-irradiation is more destructive to aliphatic chains in urushiol polymer, but it also can accelerate the polymerization of micro-amount urushi film. Py-GC/MS analysis of conventional urushi films indicates that with the increase of aging degree, the total chromatographic peak area ratio of hydrocarbons to benzene derivatives gradually increases, the peak area ratio of 3-pentadecenyl-catechol to 3-pentadecyl-catechol gradually decreases, and the peak area ratio of aging products of urushiol to 3-pentadecyl-catechol gradually increases. The above parameters were further used to evaluate the aging degree of two urushi-contained samples separately collected from the surface and interior of a carved lacquer panel in the Forbidden City, and evaluation results are in accord with the natural aging law and further verify the reliability of the proposed parameters. Research results of the present work can lay a foundation for the in-depth study of the UV-irradiation aging mechanism of urushi.
危险品化学品经营许可证（带存储）