The degradation and weathering of modern polymer coatings: assessment and monitoring of the chemical signature

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Polymer coatings are extremely common in our environment and used for protection, decoration or even sanitation of surfaces and objects. Understanding their structure-property relationship, rheology, surface chemistry, and degradation is therefore important for industry (e.g. control of production, durability, and performance), and other related fields such as art and conservation science (e.g. restoration, identification of counterfeited paintings) and criminal investigations (e.g. comparing the composition of suspected and reference paints in case of burglaries (tool paint, domestic paint), vandalism (spray paint), or car accidents (automotive paint)). Each of these fields, although facing distinct problematics, have one common analytical challenge: the coatings under analysis will potentially be subject to weathering and degradation over their lifetime. Through being exposed to the exterior environment, polymer coatings age, degrade, and acquire an altered chemical signature. The challenge for the scientific community is to understand these variations in order to predict the long-term weathering of polymer coatings. The weathering and degradation of paints is nonetheless a difficult task to apprehend, as the matrix is a dynamic medium. The degradation is a combination of many factors, including the migration or evaporation of components, and some physico-chemical modifications of the structure (oxidation, cross-linking). All these effects can further be catalyzed by heat, water (moisture), UV radiation, or biological/chemical contaminants. Additionally, the most common paint materials (i.e. acrylic, alkyd, polyurethane, polyester) have different rheologic properties and surface chemistry, and contain UV protection (hindered amines light stabilizers, HALS), heat stabilizers, mechanical modifiers, or anti-microbial additives that all contribute to their chemical signature and further increase the complexity of comprehensively evaluate their degradation. A survey of the literature shows that there is an important lack of knowledge on the degradation of polymer coatings, which has always been approached by case studies or specific applications, but remains incompletely understood at a more general level. In my Discovery research program, I intend to answer the following objectives: 1) Thorough evaluation of the influencing factors that contribute to degradation and their physical and chemical outcomes, 2) Assessment of the dating potential by a synergistic approach of the influencing factors using natural and accelerated weathering, 3) Creation of a comprehensive database of chemical signatures organized by paint compositions, analytical methods, and degradation conditions. This research will establish new analytical standards for the degradation of polymers in collaboration with the industry. Additionally, collecting and sharing the results through a database will have a direct and lasting impact on the scientific community.