Conservation treatment of oxidized paper with aqueous alkaline baths has been suspected of causing damage to the cellulose, especially at high pH levels.  There is the potential for b-elimination, a rearrangement of the bonds around the oxidized group which leads to breaking a bond at the carbon which is two positions away from the oxidized group.  Sometimes the b-position is at the C1 or C4 position that connects the glucopyranose rings along the chain, and the b-elimination reaction thus breaks the cellulose chain and causes a weakening of the paper fiber.  In order to evaluate this concern, we have oxidized cotton cellulose papers and treated them in an aqueous alkaline bath at different pH levels to determine if and when the treatment causes damage to the paper.

Current research focuses on:

• Determining if the initial method of oxidation of the paper affects the amount of paper degradation when treated in the aqueous alkaline bath.
• Evaluating the pH levels required in the alkaline baths to cause b-elimination and cellulose degradation thus causing a weakening of the paper.
• Measuring the molecular weight changes using GPC as a means of monitoring the paper degradation that occurs when treated in aqueous alkaline baths.

The alkaline bath studies show there is no damage to the paper when the pH level is ≤ 10.0 for all samples that are oxidized by UVA lamps or hydrogen peroxide, which mimics oxidation during natural aging.  For these samples the initial oxidation levels varied in the carbonyl content range of 3.3-10.7.  When the pH is 12.5, there was a very slight amount of degradation in the paper at a level of < 0.5 chain breaks (mmol/100 g cellulose).

For more information:
            Stephens et al. JAIC, 47 (2008): pgs. 201-215. (pdf)

Top of page