The Research On Poplar Veneer Aging And Mechanism Of Low-temperature Plasma Treatment

This paper is based on the study of the change of the physical-chemical characteristic of theageing veneer (including natural ageing, UV accelerated ageing and passivating). According tothe mechanism of high polymer modified with low-temperture plasma, surface morphology andchemical composition before and after plasma treatment are studied, analysising the mechanismof ageing venner modified with plasma, providing theoretical basis to modify wood suface withplasma. The purpose is to enhance utilization of wood and increase influence of plamas.Firstly the alteration of colour of veneer surface with ageing is researched. The veneersurface becomes darker, more red and yellow with the ageing time extends. The changing rateof natural ageing is obvious lower than the UV accelerated ageing and passivating.Secondly the wettability of veneer suface with ageing is studied. With the ageing timeextends,wettability basicly reduces. With UV accelerated ageing, wettability becomes worsefirst to a certain extent and then becomes better. The contact angel increment of veneer surfacewith12months natural ageing is just equvalent to48h UV accelerated ageing.Thirdly surface chemical composition and construction with UV accelerated ageing areresearched making use of infrared spectrum and scanning electron microscope. After UVaccelerated ageing, the amount of carboxyl group increased, the spectral band of ligninobviously decreased. SEM of surface of poplar veneer after552h UV accelerated ageingshows that pit obviously crased and grain of suncrack formed on the guide wall.Fourthly the dyeing property and bonding property of ageing poplar veneer modified withlow-temperture plasma are studied. The colour uniformity of ageing veneer becomes worse,tinctorial yield and dye uptake obviously decreased. After modified with plasma, the colouruniformity, tinctorial yield and dye uptake become better, but colour fastness to washing decreased.Bonding strength increased with plasma treatment, and typeⅡbonding strength increasedobvious than typeⅠ.Lastly the mechanism of ageing poplar veneer modified with low-temperuare plamas isstudied making use of scanning electron microscope,ESR and XPS. Ablation took place onveneer surface after modified with plasma, roughness of the surface increased. The spectra ofESR showed that a great deal of free radicals on surface could be generated by plasma teatment;XPS showed that: plasma treatment increased the O/C atomic ratio of the wood surface, decreased C1, increased C2and C3. These results shows that a great deal of oxygen contentgroups were generated on veneer surface after treatment.