The Effects of Adding Heartwood Extractives from Acacia confusa on the Lightfastness Improvement of Refined Oriental Lacquer

Abstract

In this study, a renewable polymeric material, refined oriental lacquer (ROL), used as a wood protective coating, and the Acacia confusa Merr. heartwood extractive, which was added as a natural photostabilizer for improving the lightfastness of ROL, were investigated. The best extract conditions for preparing heartwood extractives and the most suitable amount of addition (0, 1, 3, 5, and 10 phr) were investigated. The lightfastness index including brightness difference (ΔL *), yellowness difference (ΔYI), and color difference (ΔE *), and their applied properties of coating and film were measured. In the manufacture of heartwood extractives, the yield of extractives with acetone solvent was 9.2%, which was higher than that from toluene/ethanol solvent of 2.6%, and also had the most abundant total phenolic contents (535.2 mgGAE/g) and total flavonoid contents (252.3 μgRE/g). According to the SEM inspection and FTIR analysis, the plant gums migration to the surface of films and cracks occurred after UV exposure. The phenomena for photodegradation of ROL films were reduced after the addition of heartwood extractives. Among the different amounts of the heartwood extractives, the 10 phr addition was the best choice; however, the 1 phr heartwood extractive addition already showed noticeable lightfastness improvement. The drying times of ROL were extended and film performances worse with higher additions of heartwood extractives. Among the ROL films with different heartwood extractive additions, the ROL film with 1 phr addition had superior films properties, regarding adhesion and thermal stability, compared with the films of raw oriental lacquer.

Potential Use ofPterocarpus santalinusBark Extracts as UV-Protective Coats onHevea brasiliensisWood

“…This also specifies that the coating forms a layer between the UV radiations and the wood and protects the wood from lignin deterioration. This result is in agreement with recent findings where they found that extractives form a protective barrier against UV irradiation. ,,, …”

“…The representative diagram is illustrated in Figure . The desirable anti-UV aging property can partly lessen the discoloration of dyed wood after UV irradiation. , The result indicated that the −C–H of the side chains degraded by photodegradation, and the peroxide, benzoquinone, and carbonyl groups formed. ,, …”

“…Most of the coatings, particularly epoxy and polyurethane coatings, degrade under the influence of UV radiation since they contain aromatic structures with considerable absorption in the UV region, which leads to free radical-mediated photochemical degradation. In order to prevent or limit photodegradation of the coating, UV-absorbing chemicals are added to the coating. ,,,,− Natural RS bark extract-coated rubberwood showed various degrees of color changes upon light irradiation (Figure ). The wide array of colors exhibited by the extracts showed the potential of the extracts as natural colorants.…”

“…89,90 The result indicated that the −C−H of the side chains degraded by photodegradation, and the peroxide, benzoquinone, and carbonyl groups formed. 82,83,91 The efficacy and the anti-UV property of the natural dye are determined by the degradation the lignin undergoes in the overall process. The ∼1503 cm −1 (guaiacyl lignin) and ∼1600 cm −1 (due to aromatic C�C stretching vibration in lignin) are characteristic peaks of the lignin, 83,87,92−95 which are almost obliterated after 250 h of UV exposure, referring to the rapid lignin degradation of uncoated wood after ultraviolet radiations (Figure 6F).…”

“…This result is in agreement with recent findings where they found that extractives form a protective barrier against UV irradiation. 82,83,96,97 Biocidal Activity of Bark Extracts. The antifungal activities of the extracts of RS bark were evaluated in Petri plates inoculated with a white-rot fungus T. hirsuta (TH) and a brown-rot fungus O. placentus (OP).…”