Four and a half trillion cigarette filters—made of cellulose acetate—are discarded each year, and they do not readily break down in the environment. Meanwhile, the same type of polymer is rapidly decaying in museum collections, destroying irreplaceable cultural artefacts. This project will pin down exactly how these materials degrade, by running accelerated aging experiments and using chemical analysis techniques to track changes in the polymers’ structure and physical properties. The problem is that current knowledge treats different degradation mechanisms—such as hydrolysis and photo-oxidation—in isolation, but in real-world conditions they interact in complex ways. Without understanding those interactions, it is impossible to predict how long a cigarette filter will persist as litter, or how to slow the decay of a museum object. If this research succeeds, it could inform the design of truly biodegradable cellulose-based plastics, reducing persistent litter. It could also give conservators the tools to extend the life of heritage collections. The work is applied, tackling two concrete, high-stakes problems simultaneously.
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Cellulose-based polymers such as cellulose acetate are of increasing interest as bio-based materials. However, their environmental degradability is a complex question. Approximately 4.5 trillion cellulose acetate cigarette filters are discarded annually and these are often persistent as litter.1 In contrast, cellulose-based polymers in many museum collections have been observed to decay rapidly, leading to loss of valuable cultural heritage.2 Specific degradation mechanisms such as hydrolytic deacetylation and photolytic chain scission are known. However, an understanding of the way these degradation mechanisms interact in complex environments is needed to better understand how these materials degrade, both in the natural environment and in museums.3 This collaborative project between the UCL Institute for Sustainable Heritage and the UCL Institute for Sustainable Resources aims to understand these interactions. Relationships between photo-oxidative and hydrolytic processes will be explored, in addition to accompanying changes in physical properties. The student will conduct accelerated aging experiments and use analytical techniques such as Nuclear Magnetic Resonance (NMR) and Fourier Transform Infrared (FTIR) spectroscopies, Gel Permeation Chromatography (GPC) and tensile testing to understand changes in material properties. This project is expected to have a significant impact on both the issue of persistent plastic litter and on heritage conservation.
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