Elsässer Christina, Angelin Eva Mariasole, Montag Peter, Hilbig Harald, Grosse Christian U, Pamplona Marisa
Conservation Science Department, Deutsches Museum, Museumsinsel 1, 80538 Munich, Germany.
Chair of Non-Destructive Testing, Technical University of Munich, Franz-Langinger-Straße 10, 81245 Munich, Germany.
Polymers (Basel). 2023 Oct 11;15(20):4056. doi: 10.3390/polym15204056.
Preserving celluloid artifacts is challenging for museums, as this plastic is highly prone to degradation. Frozen, cold, and cool storage solutions are typically recommended for inhibiting the chemical degradation of celluloid. However, they are rarely implemented for three-dimensional celluloid (3D-CN) objects because low temperatures might cause irreversible effects (e.g., microcracking). This work presents the effects of four different storage temperatures (+23 °C, +13 °C, +9 °C, -15 °C) on the preservation of artificially aged 3D-CN mock-ups, aiming at understanding their effectiveness by measuring molecular weight distribution, camphor, and nitrogen contents after storage. Gel permeation chromatography (GPC) results showed that the least loss of camphor content and fewer polymer chain scissions happened at -15 °C, hinting that this temperature was the best for preservation. However, the heterogeneous nature of celluloid alteration, i.e., the development of degradation gradients in thicker 3D-CN objects (>0.5 mm), made it necessary to apply a novel sampling technique, which selectively considers several depths for analyses from the surface to the core (depth profiling). This depth profiling made monitoring the degradation evolution dependent on the storage conditions in the thicker mock-ups possible. This approach was also used for the first time to quantify the polymer chain scission, camphor loss, and denitration of historical artifacts, indicating a dramatic difference in the degradation stage between surface and core. The effectiveness of frozen storage on the chemical stability of 3D-CN after seven months could support museums to consider reducing the storage temperatures to preserve precious artifacts.
对于博物馆来说，保存赛璐珞制品具有挑战性，因为这种塑料极易降解。通常建议采用冷冻、冷藏和凉爽储存解决方案来抑制赛璐珞的化学降解。然而，对于三维赛璐珞（3D-CN）物体，这些方法很少实施，因为低温可能会导致不可逆的影响（例如微裂纹）。这项工作展示了四种不同储存温度（+23°C、+13°C、+9°C、-15°C）对人工老化的3D-CN模型保存的影响，旨在通过测量储存后的分子量分布、樟脑和氮含量来了解其有效性。凝胶渗透色谱（GPC）结果表明，在-15°C时樟脑含量损失最少，聚合物链断裂也较少，这表明该温度最适合保存。然而，赛璐珞变化的不均匀性，即在较厚的3D-CN物体（>0.5毫米）中降解梯度的形成，使得有必要应用一种新颖的采样技术，该技术从表面到核心选择性地考虑几个深度进行分析（深度剖析）。这种深度剖析使得监测较厚模型中依赖于储存条件的降解演变成为可能。这种方法也是首次用于量化历史文物的聚合物链断裂、樟脑损失和脱硝情况，表明表面和核心的降解阶段存在显著差异。七个月后冷冻储存对3D-CN化学稳定性的有效性可以支持博物馆考虑降低储存温度以保存珍贵文物。
