Surface cleaning of plastic materials of historical value can be challenging due to the high risk of inducing detrimental effects and visual alterations. As a result, recent studies have focused on researching new approaches that might reduce the associated hazards and, at the same time, minimize the environmental impact by employing biodegradable and green materials. In this context, the present work investigates the effects and potential suitability of dense carbon dioxide (CO₂) as an alternative and green solvent for cleaning plastic materials of historical value. The results of extensive trials with CO₂ in different phases (supercritical, liquid, and vapor) and under various conditions (pressure, temperature, exposure, and depressurization time) are reported for new, transparent, thick poly(methyl methacrylate) (PMMA) samples. The impact of CO₂ on the weight, the appearance of the samples (dimensions, color, gloss, and surface texture), and modifications to their physicochemical and mechanical properties were monitored via a multi-analytical approach that included optical microscopy, Raman and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopies, and micro-indentation (Vickers hardness). Results showed that CO₂ induced undesirable and irreversible changes in PMMA samples (i.e., formation of fractures and stress-induced cracking, drastic decrease in the surface hardness of the samples), independent of the conditions used (i.e., temperature, pressure, CO₂ phase, and exposure time).

Degradation of ester-based polyurethane (PUR) foams results in extensive fragmentation, stickiness, and brittleness both at surfaces and in the bulk. Current methods to conserve museum objects comprising PUR foams include consolidation with solvent-based polymeric solutions. Besides the limitations of spray and brush application for deep consolidant penetration and the impracticality of immersing large-scale objects in solutions, these methods often require large amounts of toxic solvents that are harmful for both the user and environment. Carbon dioxide can be employed as a green solvent as it can be recovered, recycled, and reused without contributing to the greenhouse effect. Supercritical carbon dioxide (scCO₂)-assisted consolidation premises are that it may carry the consolidant deeper and deposit it consistently throughout the foam, whilst ensuring minimal interaction with the surface and avoiding material losses in severely degraded objects and the use of toxic solvents. The suitability of scCO₂ as a carrier is studied, and the results compared with spray application, a commonly used traditional method. Previous studies have shown that a mixture of alkoxysilanes has great potential for reinforcing the foam’s structure and hydrophobicity when applied by immersion and other impregnation techniques. In this study, scCO₂-assisted consolidation has proven to be an effective and green alternative to consolidation by spray, reducing hazardous solvent emissions. After treatment, no visual changes were detected, the samples became less sticky, and the foam flexibility improved significantly. Analytical techniques confirmed the presence of the consolidant in all tested samples, both on the top surface and in-depth layers, in contrast to foams treated by spray.

This article presents a critical literature review on blooming in thermoplastic polyurethane (TPU)-coated fabrics. Blooming, typically described as whitish surface deposits, is a common deterioration phenomenon in TPUs in fashion and design collections. Drawing on polymer science, industrial sources, and heritage conservation studies, the review examines how blooming has been defined, investigated, and addressed in conservation practice. The literature identifies two recurrent mechanisms to explain blooming: additive migration as a physical process and hydrolysis as a chemical process. The latter, which is more commonly reported in heritage TPU artefacts, often results in the formation of adipic acid. Studies focusing on conservation remain extremely limited, with only a few case studies addressing cleaning and storage. The review highlights variability in terminology, proposed causes, and reported practices across the published literature. By synthesizing current knowledge and identifying key gaps, this article supports the development of interdisciplinary conservation strategies.