rci@rcicn.com
World map
PTLP
Bookkeeper®
tel:
+86-028-85880383
Reli
Heritage Preservation 
RCICN

Automatic
Deacidification system

Movable, efficient, automatic, single-leaf
  • Observations of paper aging and acidity
  • How to Stop Yellowing and Make Books Last
  • What Can We Do to Protect Paper From Acids
  • There are two principal chemical degradation pathways of paper
  • Acidic Paper and the More Rapid Degradation of Books
  • Challenges of Deacidification
New:
NEWS CENTER
Acidic Paper and the More Rapid Degradation of Books
Source:AIDCSC | By:unknown | posted on :2020-02-06 | 58 次浏览 | 分享到:
​People have been concerned about the premature degradation of stored books and the poor quality of the paper for a long time. Gradually it became known that acidity is a key factor in shortening the useful life of books.


People have been concerned about the premature degradation of stored books and the poor quality of the paper for a long time.  Gradually it became known that acidity is a key factor in shortening the useful life of books. The same period, the typical pH values of manufactured books became lower than 6 and continued to decrease to a range between 4.5 and about 5. A correlation between pH and the rate of strength loss was found for both accelerated and natural aging tests of the same books.  Books from previous centuries have been found to remain in relatively good condition, and such findings were generally correlated to higher pH values Especially low values of pH happened to be measured for samples manufactured in the 1960s and 1970s.  But the situation was very different for the samples that had been manufactured in the 1980s and 1990s, for which the average pH of the paper was near neutral and the number of double-folds before breakage was dramatically higher.  Not only were those relatively recent samples newer, but they also were not degrading as fast.  What happened, in order to bring about that change, was almost certainly the emergence of alkaline papermaking practices, which in just a few years has come to be dominant for the production of printing papers.

In addition to acidity present in paper at the time of its manufacture, acids are formed continually both in acidic and alkaline cellulose material due to hydrolysis or oxidation reactions, which will be described later.  Also, some acidity accumulates through absorption of pollutants from the air, particularly in urban areas.  However, the detailed effects are different, depending on whether the paper’s microstructure is acidic or alkaline:  The acids arising in the alkaline part of the microstructure, which contains alkaline reserve, presumably can be continually neutralized.  The degradation in the alkaline paper continues very slowly, and most probably the effects of the likely predominant peeling reaction can be neglected. Such a process would result in a negligible difference of the DP, longevity, brittleness, folding endurance, usability, and other mechanical and chemical quantities of paper or books.  Another alkaline degradation mechanism, the beta-elimination reaction, could be detected in the deacidified book papers.  However, it had little influence on the molar mass of cellulose in the paper compared to the beneficial effects obtained by deacidification treatment.

It is also important to keep in mind that acids are formed continually in paper by oxidation with oxygen, ozone, nitrogen, sulfur oxides, and other oxidants, in both acidic and alkaline cellulosic material, including paper and books during the whole paper lifetime . Acids arising from oxidation presumably can be continually neutralized by alkaline reserve, assuming that contact is achieved locally between the alkaline and acidic substances.  However, the neutralization of acids does not stop their formation.  Continuing generation of acidic species in paper might help to explain observations of a gradual drift to lower surface pH values over time.