透明塗料之耐候性改善及其天候變色與光變色之比較

Improvement of Weatherability of Clear Coatings and Comparison of Their Weathering- and Light-induced Discoloration

張上鎮(Shang-Tzen Chang) ； 周佰隆(Pai-Lung Chou)

《林產工業》 14卷3期 (1995/09) Pp. 373-390

https://doi.org/10.6561/FPI.1995.14(3).3

摘要

透明塗料塗裝木材暴露在戶外的環境中，往往會受天候因子影響而產生塗膜剝落、光澤度降低、變色......等缺點，本試驗針對常用的聚胺基甲酸酯及硝化纖維素透明塗料進行耐候試驗，觀察試材在耐候試驗及耐光試驗中顏色變化之差異，並利用光安定劑改善透明塗料之耐候性。由試驗結果發現硝化纖維素透明塗膜容易受天候因子影響而剝落，使得下層裸露的橡木受日光、雨水作用而變為灰黑色，耐候性較差；三種聚胺基甲酸酯塗膜則有較佳之耐候性，試材僅在試驗初期黃化，經過長時間耐候試驗後始有部份塗膜剝落。本試驗以加蓋玻璃片之耐候試驗模擬室內受陽光直射木材之劣化，結果發現對耐候性較佳塗膜而言，顏色變化與耐光試驗結果較接近，顯示該塗膜受光線因子影響較明顯；對硝化纖維素等耐候性較差塗膜而言，其變色與耐光試驗結果不盡相同，顯示水氣、空氣中污染物等因子對硝化纖維素透明塗膜仍有一定程度之影響。添加光安定劑可使聚胺基甲酸酯塗膜不易剝落。可改善其耐候性，其中以含有Tinuvin 1130之芳香族聚胺基甲酸酯塗膜及同時含有Tinuvin 1130及Tinuvin 292之脂肪族聚胺基甲酸酯塗膜耐候性較佳，但光安定劑對其天候變色則無明顯抑止效果。

關鍵字

耐候性 ； 變色 ； 黃化 ； 剝落等級 ； 硝化纖維素透明塗料 ； 聚胺基甲酸酯 ； 透明塗料 ； 光安定劑

並列摘要

Wood coated with clear coating is susceptible to discoloration, gloss loss and flaking under exposure to atmospheric factors. The weatherability of four clear coatings including nitrocellulose lacquer (NC), aromatic polyurethane coating (PU) and two aliphatic coatings (PUA and pun was evaluated based on the color change, the variation of gloss and the flaking resistance. The experimental results indicate that NC is most susceptible to flaking after exposure to atmospheric factors. After coating flaking, oak beneath NC will be exposed to rain , acidic pollutants and fungi , thereby the color of specimen turns to be gray or black. Polyurethane coatings show better flaking resistance than NC. Only yellowing of oak coated with polyurethane coatings was observed in the early stage of outdoor weathering test. From the results of weathering test behind glass (λ ＞ 300nm), it is found that the tendency of variation in color of coating with good weatherability is similar to that of artificially accelerated lightfastness test. Therefore, it reveals that change in color of those coatings is more influenced by light than by atmospheric factor. For those coatings with poor weatherabiltiy, the difference in color variations between in weathering test behind the glass and in artificially accelerated lightfastness test shows that, besides light, moisture and pollutants have some influence on the discoloration. Examination of film flaking on oak surface after weathering test illustrates that polyurethane coatings containing light stabilizers shows better flaking resistance than that without light stabilizers , and that aromatic polyurethane coating containing Tinuvin 1130 and aliphatic polyurethane coatings containing both Tinuvin 1130 and Tinuvin 292 exhibit best flaking resistance. However, the effectiveness of stabilizers on the prevention of weathering-included discoloration is not significant.

並列關鍵字

Weatherability ； Discoloration ； Yellowing ； Flaking resistance ； Nitrocellulose lacquer ； Polyurethane clear coating ； Light stabilizer