The Getty Conservation Institute, Los Angeles, California, USA.
Acc Chem Res. 2010 Jun 15;43(6):888-96. doi: 10.1021/ar1000132.
Cellulose acetate, developed about 100 years ago as a versatile, semisynthetic plastic material, is used in a variety of applications and is perhaps best known as the basis of photographic film stock. Objects made wholly or partly from cellulose acetate are an important part of modern and contemporary cultural heritage, particularly in museum collections. Given the potential instability of the material, however, it is imperative to understand the aging mechanisms and deterioration pathways of cellulose ester plastics to mitigate decomposition and formulate guidelines for storage, exhibition, and conservation. One important aspect of this process is the ability to fully characterize the plastic, because variations in composition affect its aging properties and ultimate stability. In this Account, we assess the potential of a range of analytical techniques for plastics made from cellulose acetate, cellulose propionate, and cellulose butyrate. Comprehensive characterization of cellulose ester plastics is best achieved by applying several complementary analytical techniques. Fourier-transform IR (FTIR) and Raman spectroscopy provide rapid means for basic characterization of plastic objects, which can be useful for quick, noninvasive screening of museum collections with portable instruments. Pyrolysis GC/MS is capable of differentiating the main types of cellulose ester polymers but also permits a richly detailed compositional analysis of additives. Thermal analysis techniques provide a wealth of compositional information and thermal behavior. Thermogravimetry (TG) allows for quantitative analysis of thermally stable volatile additives, and weight-difference curves offer a novel means for assessing oxidative stability. The mechanical response to temperature, such as the glass transition, can be measured with dynamic mechanical analysis (DMA), but results from other thermal analysis techniques such as TG, differential scanning calorimetry (DSC), and dynamic load thermomechanical analysis (DLTMA) are often required to more accurately interpret the results. The analytical results from this study form the basis for in-depth studies of works of art fabricated from cellulose acetate. These objects, which are particularly at risk when stored in tightly sealed containers (as is often the case with photographic film), warrant particular attention for conservation given their susceptibility toward sudden onset of deterioration.
醋酸纤维素是一种约 100 年前开发的多功能半合成塑料材料，用于各种应用，其作为摄影胶片的基础材料而广为人知。由醋酸纤维素制成的全部或部分物品是现代和当代文化遗产的重要组成部分，特别是在博物馆收藏中。然而，鉴于该材料的潜在不稳定性，了解纤维素酯塑料的老化机制和降解途径对于减轻分解以及制定存储、展览和保护的指导方针至关重要。这个过程的一个重要方面是全面描述塑料的能力，因为成分的变化会影响其老化性能和最终稳定性。在本报告中，我们评估了一系列用于醋酸纤维素、丙酸纤维素和丁酸纤维素制成的塑料的分析技术的潜力。通过应用几种互补的分析技术，可全面描述纤维素酯塑料。傅里叶变换红外（FTIR）和拉曼光谱法为塑料物体的基本特征提供了快速手段，这对于使用便携式仪器对博物馆藏品进行快速、非侵入性筛选非常有用。热解气相色谱/质谱（Py-GC/MS）能够区分主要类型的纤维素酯聚合物，但也允许对添加剂进行丰富详细的成分分析。热分析技术提供了丰富的成分信息和热行为。热重分析（TG）允许对热稳定挥发性添加剂进行定量分析，重量差曲线为评估氧化稳定性提供了一种新颖的方法。温度的机械响应，例如玻璃化转变，可以通过动态机械分析（DMA）进行测量，但通常需要来自其他热分析技术（如 TG、差示扫描量热法（DSC）和动态负载热机械分析（DLTMA）的结果来更准确地解释结果。这项研究的分析结果为深入研究由醋酸纤维素制成的艺术品奠定了基础。这些物品在储存于密封容器中时（如摄影胶片通常情况）特别容易受到损坏，因此需要特别注意保护，因为它们容易突然出现恶化。
