Effect of thermal and photochemical degradation strategies on the deterioration of cellulose diacetate

In this study, the effect of thermal and photochemical accelerated degradation on the deterioration pathways of cellulose diacetate was evaluated. The degradation induced under controlled experimental conditions was carefully monitored in order to investigate the correlation between specific degradation mechanisms and the visible signs of deterioration that are often encountered on cellulose acetate museum objects. In the time interval studied, thermally degraded samples did not show visible discoloration or noticeable vinegar smell, but appeared severely distorted. Samples degraded under UVA radiation did not show any significant sign of deterioration, while samples degraded under UVB and UVC radiations appeared discolored and released the typical vinegar odor. Samples degraded under UVB radiation were also brittle and prone to crazing. By monitoring the samples as they deteriorated over time, new insights into the degradation mechanisms were obtained. During thermal degradation, the experimental results showed that plasticizer diffusion through the polymer matrix is affected by the progressive loss of plasticizer that occurred during the degradation experiment. During photo-degradation experiments, yellowness induced by UVC and UVB radiations was found to be reversible by subsequent exposure to UVA radiation, while the depth of the degradation appeared to be one of the key factors that led to brittleness and the appearance of crazing.