透明塗裝杉木光劣化後之表面性質變化

Variations in the Surface Properties of Clear Coated China Fir after Photodegradation

張惠婷(Hui-Ting Chang) ； 張上鎮(Shang-Tzen Chang)

《林產工業》 17卷2期 (1998/06) Pp. 333-344

摘要

芳香族與脂肪族聚胺基甲酸酯透明塗裝杉木經光線照射後，塗裝材的表面仍會產生光黃化，而喪失原有的外觀，其中，以芳香族聚胺基甲酸酯塗裝材的變色較為顯著。又芳香族聚胺基甲酸酯塗膜的濕潤性也隨著照光時間增加而增大，且塗膜的紅外線光譜亦產生變化，顯示此透明塗裝材照光後表面形成具有親水性羧酸基與醌醯亞胺類等有色劣化物。而脂肪族聚胺基甲酸酯塗膜的化學結構變化輕微，接觸角也維持一定。此外，由塗膜表面硬度之增加得知塗膜的交聯度上升，照光後由於基材與塗膜界面的劣化，導致塗膜與基材的附著性降低。添加光安定劑能減緩透明塗裝杉木的光黃化及其他性質的劣化，同時，亦使塗膜與木材附著性較為穩定。但是，對於耐光性較差的杉木而言，即使以耐光性佳之透明塗料（或添加光安定劑）塗裝，照光後塗膜本身雖然改變很少，但是穿透塗膜的光線仍會引起木材之光變色與性質變化，進而使塗膜與木材的界面破壞，使塗膜的附著性降低，無法長效抑止透明塗裝杉木的光劣化。

關鍵字

木材 ； 杉木 ； 透明塗料 ； 聚胺基甲酸酯 ； 光劣化 ； 光黃化 ； 表面性質 ； 硬度 ； 濕潤性 ； 塗膜附著性

並列摘要

China fir coated with aromatic or aliphatic polyurethane coating, respectively, was proven to be readily susceptible to photoyellowing and changed the originally attractive appearance after photoirradiation. Especially the discoloration of aromatic PU coated China fir was much server. The consequences of irradiation lead to the increment of wettability of aromatic PU coated China fir. The formation of derivatives containing hydrophilic carboxyl groups and quinone imides was detected on the aromatic PU film after photodegradation according to the FTIR difference spectrum. The variations of chemical structures of the aliphatic PU film were slightly detected and the contact angle of alipliatic PU film was kept constant. In addition, the increment of surface hardness of polyurethane film revealed that irradiated PU film would turn to higher crosslinking. The deterioration of wood beneath the film and the coating, especially aromatic PU film, would result in the destruction of adhesion between the coating and wood. The addition of light stabilizers into coating could slow down the photoyellowing and degradation of properties of clear coated China fir and consequently stabilized the interface of coating and wood. However, for China fir , due to the inferior lightfastness characteristics, the results demonstrated that the discoloration induced by light could not be effectively inhibited only by coating with lightfastness finishes or finishes containing light stabilizer in the long term. It is because the UV light would penetrate through the clear film and reach the interface of wood and clear coating inducing the photodegradation of clear coated wood.

並列關鍵字

Wood ； China fir ； clear coating ； polyurethane ； photodegradation ； photoyellowing ； surface property ； hardness ； wettability ； adhesion of coating