Chromatic aberration adjustment mechanism of decorative veneers after bleaching and dyeing treatments
The chromatic aberration of decorative veneer is mainly caused by the different lignin and extractive contents in heartwood and sapwood.Lignin and phenolic substances are rich in chromogenic groups and co-chromophores,which significantly influences the coloration of wood,creating distinct differences between heartwood and sapwood.The common color difference control methods include chemical treatment,physical covering,and physicochemical combination.Using bleaching dyeing process,the color difference control method is a physicochemical combination treatment.Bleaching treatment was used to degrade the hair color substance of the heartwood,and the color of the heartwood was homogenized.The decorative veneer is endowed with a specific color by dyeing treatment to realize the directional control of decorative veneer color.To further analyze the mechanism of chromatic aberration control,the present study mainly tested and analyzed the chemical composition of black walnut veneer before and after bleaching by the scanning electron microscope(SEM),Fourier transform infrared spectroscopy(FT-IR)and X-ray photoelec-tron spectroscopy(XPS).The changes of color group content on inclusions,i.e.,lignin and other substances,in wood core sapwood were analyzed,and the mechanism of chromatic aberration adjustment was revealed.The research results indicated that △E decreased from 11.48 to 2.97 after bleaching,and dyeing treatment can provide decorative veneers with specific colors.The results of SEM,FT-IR,and XPS showed that the extractive contents in bleached decorative veneer were significantly reduced,and some fatty acid contents on the surface of the wood were removed.The decrease in O/C value during the bleaching process was mainly related to lignin degradation,and the main chro-mophore conjugated C＝O double bond was destroyed,resulting in the decrease in the content of O element.The con-jugated C=O and C＝C chromophores contained in lignin underwent partial degradation,which was the main reason for the color change of the veneer caused by bleaching treatment.The C1 content in sapwood decreased,and the C2,C3,and C4 contents increased,indicating that new oxygen-containing groups were produced in wood.After the dyeing treatment,the dye was deposited on the surface of the wood,which changed the contents of C1,C2,C3,and C4.Meanwhile,lignin degradation led to cell wall shrinkage and an increase in internal pores of the wood,which fa-cilitated the penetration of dye solution inside the veneer.During the dyeing process,the veneer did not chemically bind with the dye,but rather underwent physical adsorption.
decorative veneerheartwood-sapwood color differencebleaching treatmentdyeing treatmentmechanism of chromatic aberration adjustment
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维普
