Study On Preparation And Yellowing-Resistance Mechanism Of Fast-Drying And Yellowing-Resistant Green Tung Oil Coating

In the field of coatings,biomass materials,especially vegetable oils,have been gradually applied to the preparation of new environmentally-friendly green coatings.Tung oil,a special resource of China,is a pure natural,green and renewable biomass material,which has the fastest drying rate in natural oils and can be directly biodegraded after polymerization.However,the inherent drying speed of tung oil is slower than chemical synthetic coatings,and the paint film is prone to yellowing in the natural environment.These two major drawbacks are the biggest resistance to the expansion of tung oil.In this paper,tung oil,polymerized tung oil and decolorized tung oil were used as raw materials to explore the effects of different drier and different light stabilizers on the drying performance and photoaging resistance of tung oil,and the yellowing mechanism of the tung paint film was explored.The main contents are summarized as follows:1.With 0.6%of rare earth isooctanoate and 0.01%of cobalt isooctylate used together,surface drying time and actual drying time of raw tung oil are 2 h and 2.5 h,respectively,the hardness grade is 4 H,and the adhesion grade is 1.In the same condition,the surface drying time and actual drying time of polymeric tung oil are 0.67 h and 1 h,respectively,the hardness level is 5 H,and the adhesion is grade 1.Compared with the high-efficiency drier M2203 and CQ-150B,the composite drier has lighter color and better solubility.The FT-IR and TG analysis shows that the tung paint film prepared by the composite drier has high cross-linking degree and good heat stability.2.The optimum additive amount of UV1130 and UV292 are 2.0%and 0.4%,respectively.After 336 h of UV accelerated aging,the color difference of the modified tung paint film are 4.74 and 5.20,respectively,which decreased 32.29%and 25.71%respectively than that of the unmodified tung paint film.0.16%of nano-ZnO-modifled tung paint film after 288 h photoaging test,the color difference of tung paint film is 5.09,which is 16.97%lower than that of unmodified tung paint film,The composite light stabilizer(0.4%UV292+0.16%nano zinc oxide)modified tung paint film after aging for 336 h,the color difference is only 2.91,which is 58.29%lower than that of the unmodified tung paint film;3.The results of FT-IR and XPS spectrum of tung paint film showed that the content of C element decreased and the content of O element increased after photoaging.In the aging process,the absorption peak of C=C became weakened,the relative content decreased,and the relative content of C-C bond and C=O bond increased.Light stabilizer UV292 can delay the conversion of C=C and C-O bonds to C-C and C=O bonds,thereby protecting the tung paint film.