The role of plasticiser loss in the degradation of plastic objects in heritage collections

根据先前的研究，对文物收藏中的塑料物品的分析表明，诸如开花和“出汗”等物理迹象表明塑料降解，纤维塑料材料的收缩、开裂和断裂是这种破坏的长期表现。通过一系列分析技术，包括FT-IR和Py-GC/MS，确定了人工制品表面增塑剂的存在和特征，而它们的挥发性使得SPME-GC可以在气体排放产物中检测到它们。然而，目前只有当这些物理外观发生变化时，通过增塑剂损失引起的降解对保护人员来说才变得明显。考虑到材料性质和储存环境的早期检测方法或降解预测模型，可以使预防性保护方法在早期阶段开始，从而在可观察到的变化产生之前减缓降解机制。为了探索增塑剂损失在塑料降解中的作用，该项目将寻求制备多个相同的醋酸纤维素和PVC样品，这些样品可以进行人工老化研究并监测由此产生的降解。与史密森尼博物馆保护研究所的合作将使样品的制备与文物收藏中保存的材料的组成非常相似。将使用（半）定量成像方法（如近红外高光谱成像）尝试和验证增塑剂运输的建模，该方法将需要为该项目的目的专门开发。该项目通过与CDT的两个分支——数据创造和数据转化为知识——相结合，支持CDT的艺术、遗产和考古科学与工程。它也与EPSRC的优先事项“测量和传感”、“材料表征”和“数据到知识”保持一致。

As determined by previous studies, analysis of plastic objects in heritage collections has revealed that physical signs such as bloom and 'sweating' are indicative of plastic degradation with shrinkage, cracking and breakage of cellulosic plastic materials being the longer term manifestations of such damage. The presence and characterisation of plasticisers on artefact surfaces has been determined by a range of analytical techniques, including FT-IR and Py-GC/MS, whilst their volatile nature has allowed their detection in gaseous emission products by SPME-GC. However, degradation via plasticiser loss currently becomes apparent to conservators only when these changes in physical appearance occur. Early detection methods or predictive models of degradation which take into account a material's properties and storage environment, and could enable preventative conservation methods to begin at an earlier stage, thus slowing degradation mechanisms before observable changes result. In order to explore the role of plasticiser loss in plastic degradation, the project will seek to prepare multiple identical samples of cellulose acetate and PVC which can be subjected to artificial ageing studies and monitored for resulting degradation. Collaboration with the Smithsonian Museum Conservation Institute will enable the preparation of samples which closely resemble the composition of materials held within heritage collections. Modelling of plasticizer transport will be attempted and validated using (semi-)quantitative methods of imaging, such as near infrared hyperspectral imaging, a method that will need to be developed specifically for the purpose of the project. The project supports the CDT Science and Engineering in Arts, Heritage and Archaeology through alignment with two of its strands: Data Creation and Data to Knowledge. It also aligns with the EPSRC priorities 'Measurement and Sensing' and 'Materials Characterisation' and 'Data to Knowledge'.