Catastrophic room temperature degradation of cotton cellulose

Slow cellulose degradation at room temperature requires the application of accelerated ageing tests. After an ageing treatment, the paper samples were usually stored at standard room temperature, before being used for further studies. It was assumed previously that degradation was again very slow during the post-ageing storage. However, repeated DP measurements (6 and 1820 months after the accelerated ageing) revealed a significant decrease in the polimerization degree, as measured viscometrically, for one of the tested papers (PAPER 2). Putting the aged paper in polyethylene bags prevented, or at least slowed down, the degradation process. During the accelerated ageing and storage-ageing, the pH of the paper decreased, as shown by the contact electrode measurements. Some conclusions, concerning the storage-degradation mechanism, have been drawn. This degradation was not a result of acid hydrolysis. It is very likely determined by an oxidation process leading to the formation of carboxylic groups. Chemical centres involved in the storage-degradation are formed during the accelerated ageing. Some of them are also destroyed later on, during the ageing. The nature of these centres remains unknown. After accelerated ageing, cotton cellulose degradation at room temperature is so fast (0.5 DP units per day) that the effect cannot be ignored. Any characterization of paper samples should be done as soon as possible after the thermal treatment. If this is impossible, the time lapse between the end of accelerated ageing and the date of a measurement should be recorded.