The Effects of Adding Different HALS on the Curing Process, Film Properties and Lightfastness of Refined Oriental Lacquer

Abstract

Oriental lacquer is a natural polymeric coating with a satiny texture and excellent characteristics, such as chemical resistance and durability. However, the poor lightfastness resulted in the natural aromatic structures of the urushiol structures limited its suitability for outdoor application. This study aimed at the improvement of the lightfastness by adding the different hindered amine light stafbilizers (HALS) with 2 phr addition as well as the effects on the coating and film property of the refined oriental lacquers (RL). The Cryptomeria japonica plate, glass sheets, and the other substrates were used for finishing. The results showed that the lightfastness of RL film was obviously improved by adding 2 phr HALS of Bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (H90) containing -NH group and Bis (1,2,2,6,6-pentamethyl-4-piperidinyl)-[[3,5-bis(1,1-dimethyl ethyl) -4-hydroxyphenyl] methyl] butylmalonate (H60) containing -NCH3 groups. The HALS additions increased the pH value of RL and improved the activities of laccase-catalyzed reaction. Meanwhile, the oxidative polymerization of the side chains of RL was inhibited, caused by a radical scavenging ability of HALS. The changes in the drying process affected not only the curing time, but also the film properties. Among the 2 phr additions of different HALS, the film containing H90 had the best lightfastness. Meanwhile, it kept the most similar properties with RL and shortened the drying time of RL, and it was selected as the best HALS addition under 2 phr in this study.

Effects of Adding Antioxidants on the Lightfastness Improvement of Refined Oriental Lacquer

“…The coating properties of ROL with different contents of AO-N are listed in Table 4 . The ROL with and without AO-N had the same pH values of 3.4–3.5, meaning that the activity of laccase was be affected by the addition of the antioxidant, and the optimum pH value of ROL with the best activity of laccase is 3.0~5.0 [ 11 , 12 ]. The viscosity of ROL increased with increasing amount of AO-N added.…”

“…The SEM images of ROL films with different contents of AO-N before and after UV exposure of 192 h are shown in Figure 5 . The ROL film without AO-N had more white particles of plant gum (as Figure 5 b), which was due to severe photo-degradation under UV exposure [ 2 , 12 , 13 , 28 ]. However, the white spots were less prevalent in the ROL films with AO-N after UV irradiation.…”

“…In addition, cracking, chalking, gloss loss, and white spots are found on the film’s surface after UV exposure. These phenomena are due to the photo-degradation and cause a plant gum, which is another component of oriental lacquer resulting from the coating network structure [ 2 , 12 , 13 ].…”

“…Hong et al [ 11 ] added HALS and a benzotriazole UV absorber to an oriental lacquer to enhance its photo-stabilization. In our previous reports [ 12 , 13 , 18 ], effects of a titanium dioxide (TiO 2 ) UV screener and different types of HALS addition on the lightfastness improvement of a refined oriental lacquer were examined. In this study, the antioxidant additions were further investigated for improving the lightfastness of ROL.…”

Polyimide Fibers with High Strength and High Modulus: Preparation, Structures, Properties, and Applications

“…Huang et al introduced 2‐(4‐aminophenyl)‐5‐aminobenzoxazole (BOA) into the BPDA/PDA polymer backbone. The mobility of the polymer chains was improved and the fibers were subjected to large drawing during thermal treatment . Yin et al investigated the effect of BIA/BOA molar ratio on the performance of BPDA/BIA/BOA PI fibers.…”