Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/65821
標題: 紙質文物之光劣化防治
Photo-aging Prevention of Paper-based Cultural Relics
作者: 曾棓敬
Zeng, Peng-Ching
關鍵字: 紙質文物;光劣化;聚乙二醇;ESCAL;球摩木質素
出版社: 森林學系
摘要: 
摘 要
為了減少紙質文物之光劣化,本研究分別嘗試以物理隔離法、PEG添加法加以探討之外,並且嘗試了解木質素的存在是否影響碳水化合物的降解。
(一)物理隔離法
試驗中所採用熱壓護貝法和ESCAL塑膠袋密封法兩種方法,以降低氧氣濃度和隔絕紫外線的兩種物理性處理,對於延緩紙張表面白度下降,以及防止紙力之衰退,皆具有良好的效果。尤其是以ESCAL塑膠袋密封法之效果最好,確實可以有效減緩紙張表面白度下降,同時亦能防止碳水化合物產生劣化降解,以保持紙質文物的外觀和物理性質。
對於化學紙漿製成之紙張(道林紙、濾紙)來說,在日光劣化之過程中,其白度下降不明顯,甚至有光漂白的現象。然而,日光照射確實會讓紙張力學性質受到損傷,亦即紙質文物的表面黃化與否,並不能作為評估光劣化程度的唯一指標。
(二)化學藥品添加法
本試驗中紫外線照射之最初5個小時內,PEG分子都無法立即產生抑制光變色的效果,然而照射20個小時之後,PEG抑制光變色效果才會顯現,紙張的白度變化逐漸穩定。
試驗結果顯示出在過高的PEG含浸濃度(10 %、15 %、20 %)時,高分子量PEG(10,000以上)的抑制光變色效果提升有限,且經過長期日照後,可能反而有發生紙張脆化之問題。因此,建議以低濃度之PEG含浸液(2 %、4 %、6 %)、低分子量PEG(4,000、400)較適用於保存紙質文物方面。
(三)木質素光黃化影響碳水化合物降解
經日光照射的球磨木質素FT-IR分析光譜中,其官能基變化情形與木質素黃化反應機制符合。因此,磨木質素或木質素模式化合物在日照實驗中發生光化學反應後,極可能會導致碳水化合物之聚合度下降,進而促使紙力強度下降。

Summary
In order to reduce the photo-aging of paper-based cultural relics, this study made some trials through physical prevention (blocking of oxygen and UV with polymer film or bag), and chemical processing (PEG impregnation). Furthermore, lignin-involved carbohydrates degradation has also been discussed.
1. Physical prevention
In this experiment, two methods were applied by using hot-sealing film and enclosure in ESCAL plastic bags to protect paper-based cultural relics from ultraviolet exposure and oxygen. These physical isolation processing could keep the brightness and paper strength to some satisfactory degree, especially good for lignin-rich paper such as newsprint. Taking out of oxygen and blocking UV irradiation, the effect of ESCAL bag on preserving carbohydrates' degree of polymerization was quite well.
In papers made of chemical pulp (Paper H and Paper F), the brightness could be held or even slightly photo-bleached after sunlight exposure, however, the physical strength of these papers did substantially decline. As a subsequent conclusion, the yellowing of paper should not suitably be the only criterion in the evaluation of photo-aging of papers.
2. Impregnation with PEGs
Exposing in the UV irradiation, the brightness of PEG-impregnated BCTMP hand sheet samples decreased remarkably in the first 5 hours, however, became gradually steady after 20 hours exposure.
The experimental results also showed that impregnation with high molecular weight PEGs (MW>10,000) in higher solution consistency (10 %, 15 %, 20 %) did not hold the brightness effectively. In addition, these PEG-impregnated samples became weak and brittle, mainly due to the long exposure of sunlight or UV, and behaved similarly to that of high molecular weight plastics.
Impregnation with low molecular weight PEGs (MW 4,000 and 400), and/or in low consistency of solution (2 %, 4 %, 6 %) are suitable for the preservation of BCTMP-containing papers from photo aging.
3. The degradation of lignin-involved carbohydrates
Attempting to clarify whether there is the possibility of lignin-involved carbohydrates degradation, impregnation of filter paper with milled wood lignin(MWL)and 3 lignin model compounds were processed.
After sunlight exposure, filter papers impregnated with MWL or lignin model compounds received more carbohydrates degradation in comparison with untreated ones. This result gave proof to show photochemical reaction of these lignin substances probably is the reason
of more intensive carbohydrates degradation and the weakening of paper strength.
In the FT-IR spectra analysis of sunlight irradiated MWL, the changes of organic functional groups match the photo-yellowing reaction mechanism of lignin as suggested by the former researchers.
URI: http://hdl.handle.net/11455/65821
Appears in Collections:森林學系

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