抽出成分對木材光劣化的影響

Effect of Extracts on Wood Photodegradation

張資正(Tzu-Cheng Chang)

指導教授 ： 張上鎮

國立臺灣大學/生物資源暨農學院/森林環境暨資源學研究所/碩士(2010年)

https://doi.org/10.6342/NTU.2010.02880

摘要

本研究利用傅立葉轉換紅外線光譜、紫外光/可見光光譜與光電子能譜儀分析已萃取與未萃取柳杉與相思樹心材經加速耐光試驗與淋洗試驗後表面之顏色與化學結構變化，探討抽出成分對木材光劣化的影響，以了解抽出成分在木材光劣化過程中所扮演的角色。由表面顏色變化可知不含抽出成分之柳杉與相思樹的心材照光後皆會產生黃化的現象。然而含有抽出成分之柳杉心材，其原本之紅色會因照光而逐漸褪色，材色亦會因此而逐漸黃化，但色差值增大之輻度較不含抽出成分之柳杉為低；含有抽出成分之相思樹心材，其原本之材色會更加深，雖然色差值變化較大，但經長時間照光後，其變化趨勢則較不含有抽出成分之試材緩和。由化學結構變化分析結果可知抽出成分會吸收部份光能而先行氧化或劣解，進而產生羥基、羰基以及羧酸基等有色劣化衍生物，因此緩和木質素的劣化，並減緩了水溶性羰基與醌類等劣化衍生物的產生。此外，由於木質素結構之差異，相思樹木質素之劣化程度會較柳杉大。柳杉與相思樹心材纖維素之結晶度皆因照光而降低，然而柳杉抽出成分能減緩心材結晶度下降的程度，但相思樹抽出成分卻會加速心材結晶度的下降；此外，無抽出成分相思樹之纖維素有較好之結晶強度，因此照光後之結晶度降低程度較小。綜合上述結果可知，抽出成分之存在確實能減緩木材的光劣化，並減少水溶性劣解物的形成，但因抽出成分之差異，僅只有柳杉抽出成分能減緩心材照光後纖維素結晶度的降低。

關鍵字

相思樹 ； 柳杉 ； 結晶度 ； 抽出成分 ； 木質素 ； 光劣化

並列摘要

The main purposes of this study were to investigate the effects of extractives on wood photodegradation and to clarify their roles during the process by observing the changes in surface color and chemical structures of extracted and non-extracted Cryptomeria japonica and Acacia confusa heartwoods. Results from the measurement of color changes showed that yellowing induced by light occured on extracted C. japonica and A. confusa specimens’ surface. Although the red color of non-extracted C. japonica was faded and followed by turning into yellow gradually after irradiation, the ΔE* value of non-extracted C. japonica specimen increased less than that of extracted specimen. While the color of non-extracted A. confusa specimen became dark and the ΔE* value of non-extracted specimen increased more than that of extracted one after irradiation. Nevertheless, the ΔE* value of non-extracted A. confusa specimen changed lesser than that of extracted one, after long term irradiation. The changes of chemical structures indicated that the extractives would be oxidated or degraded after absorbing light, thus the hydroxyl, carbonyl and carboxylic colored derivatives produced. For this reason, the degradation rate of lignin slowed down and the water soluble carbonyl and quinoid derivatives produced lesser. Additionally, the different lignin types lead to the higher degradation degree in A. confusa than that in C. japonica lignin. In the bargain, all C. japonica and A. confusa cellulose crystallinity index were downscaled by light. Howbeit, the crystallinity index was decreased less when C. japonica extractives exist, the opposite result showed in A. confusa. This result also exhibited the crystalline intensity of A. confusa cellulose was much better than that in C. japonica extracted specimen. In conclusion, extractives play an essential role in retarding the photodegradation of wood and the rate of wood degradation was decreased by the presence of extractives, but only C. japonica extractives can protect the crystalline cellulose against light.

並列關鍵字

Acacia confusa ； Cryptomeria japonica ； Crystallinity index ； Extractive ； Lignin ； Photodegradation

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