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Throughout the 20th Century, plastics found extensive use in fashion, art, and design due to their versatile nature. However, their degradation over time poses challenges, impacting material integrity, particularly in museum collections. To tackle this issue, different scientific techniques have been employed to study polymers. In this work, a complementary multi-analytical approach is proposed to investigate the light stability of ABS compounds, selecting LEGO® bricks as reference material. The method is based on fluorescence emission and lifetime integrating point-like analysis and imaging systems to corroborate chemical and spatial information specifically addressed at the surface level. The latter has shown promising results in studying ABS objects, offering insights into degradation and aiding conservation efforts.

The 1960s saw the emergence of plastic as an indispensable component in various fields, including art and design. Acrylonitrile-butadiene-styrene (ABS) is widely used by artists and designers for a range of applications including sculptures and decorative pieces. Consequently, the necessity to conserve ABS from deterioration is a crucial issue in the field of cultural heritage preservation. Many studies have highlighted the criticality of the stability of the polybutadiene component when exposed to light. We propose a new multimodal spectroscopic approach to assess the conservation status of plastic design objects. This non-destructive approach combines correlative Brillouin and Raman micro-spectroscopy (BRaMS), external reflection IR spectroscopy and portable NMR relaxometry. BRaMS is a novel non-destructive technique in the field of heritage conservation, allowing simultaneous monitoring of chemical and mechanical changes occurring at the sample surface. The present study focused on photochemically aged LEGO® bricks made of ABS and aimed to i) correlate chemical and mechanical changes induced by light exposure and ii) introduce a surface degradation index (SDI), measurable in situ by external reflection IR spectroscopy, to assess the state of conservation of plastic artefacts. Finally, non-invasive investigations were carried out on real design objects using the MObile LABoratory (MOLAB) platform.

Acrylonitrile butadiene styrene (ABS) is a thermoplastic polymer widely used in several everyday life applications; moreover, it is also one of the most employed plastics in contemporary artworks and design objects. In this study, the chemical and thermal properties of an ABS-based polymer and its photo-degradation process were investigated through a multi-analytical approach based on thermal, mass spectrometric and spectroscopic techniques. LEGO® building blocks were selected for studying the ABS properties. First, the composition of unaged LEGO® bricks was determined in terms of polymer composition and thermal stability; then, the bricks were subjected to UV–Vis photo-oxidative-accelerated ageing for evaluation of possible degradation processes. The modifications of the chemical and thermal properties were monitored in time by a multi-technique approach aimed at improving the current knowledge of ABS photodegradation, employing pyrolysis online with gas chromatography and evolved gas analysis, coupled with mass spectrometric detection (Py-GC-MS and EGA-MS), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and corroborated by external reflection FT-IR spectroscopy. The multimodal approach provided new evidence on the two-step degradation pathway proposed for ABS, defining molecular markers for polybutadiene oxidation and styrene-acrylonitrile depolymerization. Moreover, the results highlighted the feasibility of correlating accurate compositional and thermal data acquired by bulk techniques with external reflection FT-IR spectroscopy as a non-invasive portable tool to monitor the state of conservation of plastic museum objects in-situ. [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO2) has been used in numerous paintings since its creation in the early 1920s. However, due to this relatively recent adoption by the art world, we have limited knowledge about the nature and risk of degradation in museum environments. This study expands on the existing understanding of TiO2 facilitated degradation of linseed oil, by examining the effect of visible light and crystallographic phase (either anatase or rutile) on the reactivity of TiO2. The present approach is based on a combination of experimental chemical characterization with computational calculation through Density Functional Theory (DFT) modeling of the TiO2-oil system. Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FT-IR) enabled the identification of characteristic degradation products during UV and visible light aging of both rutile and anatase based paints in comparison to BaSO4 and linseed oil controls. In addition, cratering and cracking of the paint surface in TiO2 based paints, aged under visible and UV–vis illumination, were observed through Scanning Electron Microscopy (SEM). Finally, Density Functional Theory (DFT) modeling of interactions between anatase TiO2 and oleic acid, a fatty acid component of linseed oil, to form a charge transfer complex explains one possible mechanism for the visible light activity observed in artificial aging. Visible light excitation of this complex sensitizes TiO2 by injecting an electron into the conduction band of TiO2 to generate reactive oxygen species and subsequent degradation of the oil binder by various mechanisms (e.g., formation of an oleic acid cation radical and other oxidation products). [ABSTRACT FROM AUTHOR]