| Oil paintings colored on Chinese ancient wooden architectures have a special place in the history of China,which are developed by a long-term experience accumulation forming a set of unique traditional technology.These oil paintings made by natural materials show outstanding enduring qualities which are closely related to the traditional craft.Despite of these ancient paintings suffering various diseases,they still have superior performances compared with coating materials today.Hence,to explore the scientific essence in the excellent craft of drawing oil paintings on ancient buildings is of great significance.It will not only help to understand the interaction among the natural materials involved in traditional craft,but also have a practical significance to disease treatment of old paintings,inheritance and improvement of traditional craft,and the study of composite materials.Unfortunately,there are rare reports on the ancient oil painting made by the traditional craft from a scientific perspective.On the foundation of the previous research in our group,this thesis focuses on the traditional craft of refined tung oil.It aims at revealing the role of two minerals,Zhangdan and Tuzi,in the process of tung oil refining,and the influence of Zhangdan and Tuzi on the polymerization and curing of tung oil in the traditional craft.To achieve the above goals,this paper carried on the research from three aspects,and obtained the following research results and conclusions.First of all,the effects of Zhangdan and Tuzi on the curing behavior of tung oil were studied.Using 1HNMR,XRD,energy dispersive x-ray spectrum of tungsten hairpin filament scanning electron microscope(SEM-EDX)and XPS characterized the raw materials involved in tung oil refining.The microphotography of cured film of tung oil was recorded by polarizing microscope,tungsten hairpin filament scanning electron microscope and laser scanning confocal microscope.The mechanical properties of the cured oil film were determined by universal testing machine,dynamic viscoelastic spectrometer(DMA).All the results indicate that in the following.(1)The raw tung oil mainly consists of octadecyl conjugated triene-9,1 1,13-triglycerate.The main component of Zhangdan is lead trioxide;Tuzi is a complex of various oxides containing pyrolusite.(2)Zhangdan and Tuzi have a strikingly positive effect on increasing the curing speed of the surface of tung oil,shortening the curing time,and improving the smoothness of the oil film.(3)Tuzi benefits to improve the toughness of oil film,and Zhangdan helps to enhance stiffness.The mechanical properties of oil film could be improved by adding Zhangdan and Tuzi at a certain proportion.The second part of the work investigated the different functions of Zhangdan and Tuzi in the process of tung oil refining.The mechanism that Zhangdan facilitates tung oil to generate carboxylate and hydroxy was studied by IR,contact angle determination,SEM and XPS.The respective role of Zhangdan and Tuzi played in the polymerization of tung oli was analyzed using chemiluminescence,electron spin resonance(EPR),rheometer,UV-Vis absorption spectrometer(UV-Vis),and matrix-assisted laser resolution-time-of-flight mass spectrometer(MALDI-TOF-MS).Using SEM-EDX,UVVis,IR and chemiluminescence technology studied the effect of Tuzi on the homogenization during tung oil curing.The results show that(1)Zhangdan could promote the occurrence of ?-scission of conjugated bonds of tung oil to form carboxylic acid lead and alcohols at 210?.Meanwhile,Zhangdan was involved in the reaction,where the main component red lead converted to yellow lead and finally to carboxylic lead.(2)The main role of Zhangdan played in tung oil polymerization is to promote the generation of hydroperoxide,while Tuzi is used as a catalyzer to promote the occurrence of Haber-Weiss reaction of hydroperoxide generating peroxy radicals,singlet oxygen and alkyl radicals.(3)Tuzi inhibits stratifying and enhances homogeneity,improving adhesive strength and smoothness.In the third part,the mechanism of the synergistic effect of Zhangdan and Tuzi on the curing behavior of tung oil was revealed.By observation of the micromorphology of the cross section of tung oil film,and the macro appearance at the interface of Zhangdan oil and Tuzi oil using SEM studied the synergistic effect of Zhangdan and Tuzi on the production of air hole for refined tung oil.Employing oxygen uptake determination,EPR,and chemiluminescence technique explored the polymerization mechanism of refined tung oil.Using IR,SEM-Mapping,XPS,UV-Vis,chemiluminescence,and rheology characterizations investigated the effects of nitrogen and oxygen on the polymerization of refined tung oil respectively.The results indicate that(1)the coexistence of both Zhangdan and Tuzi facilitates the generation of pore structure.This structure makes air easy to enter into the inner of the formed oil film,shortening the completely curing time of tung oil.(2)In the process of refining tung oil when Zhangdan and Tuzi coexists,Zhangdan promotes the generation of hydroperoxide,while Tuzi has an inhibiting effect on it.These two opposite effects balance the polymerization rate of tung oil at the interior and the surface of the film during curing,achieving the synchronization of the dry at the surface and interior.(3)Nitrogen has a similar effect as Tuzi,inhibiting the generation of hydroperoxide,and promotes Zhangdan to convert to carboxylate,improving the curing speed and increasing the molecular weight.This thesis proposed a point that there is an important synergistic effect among various materials involved in the tung oil refining craft,which perfect scientific principles involved in the process of tung oil refining and film-forming.It provides new insights into the scientific restoration of colored paintings on ancient architectures and the treatment for the oil paintings peeling off from the architecture.Besides,it gives theoretical support,to some extent,to the exploration of tung oil-based coatings which are environmentally friendly. |
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