arXiv subjects

Sonia Bujok

Publications and source records attributed to Sonia Bujok.

3 recordsLinked to original sources

arXiv2026

Phase Separation in Heritage Objects Made of Plasticised PVC: the Case of Joseph Beuys Multiples

This work addresses the advanced degradation of plasticised PVC boards, which constitute Joseph Beuys multiples Phosphorus-Cross Sled, focusing on the mechanisms responsible for the extensive exudation of a viscous liquid. A multi-analytical approach combining chromatographic, spectroscopic, microscopic, and mechanical techniques was employed to characterise both the exuded surface layer and the polymer bulk, and to evaluate the consequences of degradation for long-term mechanical behaviour. The experimental results are supported by density functional theory simulations, which indicate a thermodynamic driving force for plasticiser migration towards the PVC surface and its tendency to self-associate. These molecular-level insights provide a mechanistic explanation for the observed migration and exudation phenomena. Overall, the study outlines a coherent deterioration pathway for exudate-covered plasticised PVC. The application of NMR spectroscopy proved to be an efficient method for studying accelerated migration of the plasticiser in PVC, opening the path to the development of non-destructive, in situ preventive conservation tools, supporting the early identification of PVC artefacts or parts of a collection that are at risk of severe phase separation.

cond-mat.mtrl-sci↗

arXiv2025

Effect of Accelerated Thermal Degradation of Poly(Vinyl Chloride): The Case of Unplasticized PVC

The thermal degradation of unplasticized poly(vinyl chloride), PVC, was comprehensively investigated through the application of spectroscopic techniques, as well as contact angle measurements (CA), dynamic mechanical analysis (DMA), and size-exclusion chromatography (SEC). To study the effect of relative humidity (RH) on the deterioration of unplasticized PVC, two regimes of accelerated degradation experiments were selected: low RH (max. 30% RH) and high RH = 60% levels, which corresponds to usually the highest RH in heritage institutions equipped with an HVAC system. Nuclear magnetic resonance (NMR) and infrared spectroscopy (FTIR) did not reveal any significant changes in the material during its degradation up to 20 weeks at temperatures ranging from 60{\deg}C to 80{\deg}C. Notable changes were observed in the Raman and UV-Vis spectra, indicative of the formation of conjugated carbon-carbon double bonds. The formation of polyenes was responsible for the yellowing of samples. Notwithstanding, the aforementioned changes did not lead to a notable decline in the mechanical properties, as evidenced by DMA and SEC measurements. EPR measurements demonstrated the formation of 2 radicals at 60{\deg}C, and in the sample degraded at 80{\deg}C the presence of radicals was evident. This indicates that a radical degradation mechanism cannot be excluded even at such low temperatures.

cond-mat.mtrl-sci↗

arXiv2025

Migration of phthalate plasticisers in heritage objects made of poly(vinyl chloride): mechanical and environmental aspects

To clean or not to clean? The solution to this dilemma is related to understanding the plasticiser migration which has a few practical implications for the state of museum artefacts made of plasticised poly(vinyl chloride) - PVC and objects stored in their vicinity. The consequences of this process encompass aesthetic changes due to the presence of exudates and dust deposition, an increase in air pollution and the development of mechanical stresses. Therefore, this paper discusses the plasticiser migration in PVC to provide evidence and support the development of recommendations and guidelines for conservators, collection managers and heritage scientists. Particularly, the investigation is focused on the migration of the ortho-phthalates representing the group of the most abundant plasticisers in PVC collections. The predominance of inner diffusion or surface emission (evaporation) determining the rate-limiting step of the overall migration process is considered a fundament for understanding the potential environmental and mechanical risk. According to this concept, general correlations for various ortho-phthalates are proposed depending on their molar mass with the support of molecular dynamics simulations and NMR diffusometry. The study reveals that for the majority of the PVC objects in collections, the risk of accelerated migration upon mild removal of surface plasticiser exudate is low. Thus, surface cleaning would allow for diminishing dust deposition and air pollution by phthalate-emitting objects in a museum environment. Bearing in mind simplicity and the need for fast decision-supporting solutions, the step-by-step protocol for non-destructive identification and quantification of plasticisers in objects made of or containing plasticised PVC, determination of the physical state of investigated artefacts and rate-limiting process of plasticiser migration is proposed.

cond-mat.mtrl-sci↗