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16 pages, 5644 KiB

Open AccessArticle

Advantages of External Reflection and Transflection over ATR in the Rapid Material Characterization of Negatives and Films via FTIR Spectroscopy

by Diego Estupiñán Méndez and Thorsten Allscher

Polymers 2022, 14(4), 808; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14040808 - 19 Feb 2022

Cited by 7 | Viewed by 4062

Abstract

The identification of film support material is of utmost importance for evidence-based collection management in cultural heritage institutions, especially the identification of cellulose nitrate for fire safety reasons, as nitrate is highly flammable and deteriorates over time. Cellulose nitrate film was used by [...] Read more.

The identification of film support material is of utmost importance for evidence-based collection management in cultural heritage institutions, especially the identification of cellulose nitrate for fire safety reasons, as nitrate is highly flammable and deteriorates over time. Cellulose nitrate film was used by photographers and movie filmmakers from its release in the 1880s to the 1950s. Cellulose acetate, being called safety film, gradually began to replace cellulose nitrate, as it is not flammable. Despite its non-flammable properties, cellulose acetate also deteriorates in hazardous ways. Therefore, identification of cellulose nitrate and cellulose acetate in collections is imperative for preservation and risk management to collections and humans. Large photographic collections can easily contain several thousand negatives or more, so a rapid, non-invasive and reliable method is needed. Traditional identification methods, such as destructive chemical tests, are sometimes unreliable, and spectroscopic analyses are normally time-consuming. To overcome these issues, rapid material characterization was performed in transflection mode with a Fourier-transform infrared (FTIR) spectrometer equipped with an external reflectance module and an additional aluminum-foil reflector. With this newly developed method, the support material (cellulose nitrate, cellulose acetate and polyester) of about 99.8% of all films can be determined within two seconds of measuring time, without any further spectral processing. Very distinctive spectral patterns are obtained with this new method, regardless of which side of the film is being analyzed. A simple visual inspection of the raw spectrum is usually sufficient to determine the film support identity. A detailed comparison of the various FTIR techniques shows the advantages of the transflection measurement for the material characterization of film support layers. This newly developed method enables the non-invasive, rapid and unambiguous material identification of even large film collections in a short time. Full article

(This article belongs to the Special Issue Historical Synthetic Polymers: Recent Advances in the Characterization and Preservation of Cultural Heritage)

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58 pages, 23625 KiB

Open AccessArticle

Material Analysis and a Visual Guide of Degradation Phenomena in Historical Synthetic Polymers as Tools to Follow Ageing Processes in Industrial Heritage Collections

by Till Krieg, Cristian Mazzon and Elena Gómez-Sánchez

Polymers 2022, 14(1), 121; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14010121 - 29 Dec 2021

Cited by 7 | Viewed by 2976

Abstract

Identifying the most vulnerable plastics and monitoring their deterioration is one of the main problems within heritage collections with historical synthetic polymers. Gathering and interpreting data about material and degradation phenomena in a collection reveals its conservation needs. A systematic survey of the [...] Read more.

Identifying the most vulnerable plastics and monitoring their deterioration is one of the main problems within heritage collections with historical synthetic polymers. Gathering and interpreting data about material and degradation phenomena in a collection reveals its conservation needs. A systematic survey of the collection can help towards this purpose. Surveys aiming at inspecting and documenting damages rely on several tools in order to fulfill their purpose. Firstly, objective descriptions of the damages that may appear, and secondly, the means of acquiring and interpreting material information. To address these needs, this article presents (a) a visual damage catalogue of degradation phenomena in plastic and rubber materials, and (b) the implementation of Fourier-transform infrared spectroscopy (FTIR) and pyrolysis–gas chromatography–mass spectrometry (py-GCMS) for the identification of analytically challenging rubber materials and of blooming phenomena. The damage catalogue is based solely on visual and olfactory signs, so that the assessment is independent of possible causes of damages and underlying processes, with the purpose of allowing objectivity to prime over interpretation. The limitations of the use of FTIR in the identification of heavily compounded rubbers in museum surveys is highlighted, and examples are presented. The use of py-GCMS on these cases conveniently allowed the identification of the constituting monomers of several rubber materials where FTIR could not provide a univocal classification of the material present. The study of several cases of blooming allowed the identification of diverse compositions and origins, showing that the description of a degradation phenomenon is only the first step towards its understanding. Unveiling the nature of a particular case of blooming is particularly critical when conservation treatments, such as the removal of a (potentially protecting) layer, are planned. For this purpose, attenuated total reflection-FTIR (ATR-FTIR) as a surface technique was particularly useful. Full article

(This article belongs to the Special Issue Historical Synthetic Polymers: Recent Advances in the Characterization and Preservation of Cultural Heritage)

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17 pages, 4194 KiB

Open AccessArticle

Tracing Poly(Vinyl Acetate) Emulsions by Infrared and Raman Spectroscopies: Identification of Spectral Markers

by Susana França De Sá, Carolina Viana and Joana Lia Ferreira

Polymers 2021, 13(21), 3609; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13213609 - 20 Oct 2021

Cited by 9 | Viewed by 2944

Abstract

Vinyl emulsions started to be used by artists in paintings at least since the early 1960s, being now present in several artworks worldwide. However, different vinyl formulations can result in distinct behaviours over time, and if some artworks are currently showing a good [...] Read more.

Vinyl emulsions started to be used by artists in paintings at least since the early 1960s, being now present in several artworks worldwide. However, different vinyl formulations can result in distinct behaviours over time, and if some artworks are currently showing a good condition, others already show damages due to the use of compositions more susceptible to degradation. For this reason, it is fundamental to identify the main components in the vinyl acetate-based (VAc-based) emulsion. This work focuses on the molecular study of VAc-based emulsions by infrared and Raman spectroscopies. It aims at deepening the knowledge on the variability of the composite formulation and on the identification of characteristic bands and spectral profiles (identified as spectral markers) for both polymer and additives. To this end, a broad set of vinyl emulsions was gathered, including reference materials, historical commercial brands in use by Portuguese artists, and commercial brands collected from industrial companies. The entire set includes vinyl homopolymers produced for the purpose of the study and known formulations of vinyl homopolymers and copolymers, with and without plasticisers, according to technical data sheets and previous studies. Furthermore, unknown formulations have been included to validate the usefulness of the identified spectral markers. This set has been studied in the form of solid films deposited in glass slides by infrared spectroscopy in attenuated total reflection mode (ATR-FTIR) and micro-Raman spectroscopy (µ-Raman), both conducted in situ. As conclusions, the combined use of ATR-FTIR and µ-Raman proved to be very useful as different spectral markers were detected by each technique, confirming their complementarity. Besides the clear identification of vinyl acetate-based emulsions by both techniques, it was also possible to suggest spectral markers for the copolymerisation of vinyl acetate with vinyl versatate by µ-Raman, the stabilisation of the emulsion with poly(vinyl alcohol) by ATR-FTIR, and the addition of phthalates or benzoates plasticisers by both ATR-FTIR and µ-Raman. Full article

(This article belongs to the Special Issue Historical Synthetic Polymers: Recent Advances in the Characterization and Preservation of Cultural Heritage)

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27 pages, 3748 KiB

Open AccessArticle

Discoloration of Historical Plastic Objects: New Insight into the Degradation of β-Naphthol Pigment Lakes

by Anna Micheluz, Eva Mariasole Angelin, João Almeida Lopes, Maria João Melo and Marisa Pamplona

Polymers 2021, 13(14), 2278; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13142278 - 12 Jul 2021

Cited by 11 | Viewed by 4045

Abstract

Light is a determining factor in the discoloration of plastics, and photodegradation processes can affect the molecular structures of both the polymer and colorants. Limited studies focused on the discoloration of heritage plastics in conservation science. This work investigated the discoloration of red [...] Read more.

Light is a determining factor in the discoloration of plastics, and photodegradation processes can affect the molecular structures of both the polymer and colorants. Limited studies focused on the discoloration of heritage plastics in conservation science. This work investigated the discoloration of red historical polyethylene (PE) objects colored with PR 48:2 and PR 53:1. High-density and low-density PE reference polymers, neat pigment powders, and historical samples were assessed before and after accelerated photoaging. The applied methodology provided insight into the individual light-susceptibility of polyethylenes, organic pigment lakes, and their combined effect in the photoaging of historical plastic formulations. After light exposure, both PE references and historical samples yellowed, PR53:1 faded, and PR 48:2 darkened; however, both organic pigments faded severely in the historical samples. This highlights the role played by the plastic binder likely facilitating the pigment photofading. Fourier transform infrared spectroscopy and mass spectrometry techniques—EGA-MS, PY-GC/MS, and TD-GC/MS—were successfully employed for characterizing the plastic formulations and degradation. The identification of phthalic compounds in both aged β-naphthol powders opens new venues for studies on their degradation. This work’s approach and analytical methods in studying the discoloration of historical plastics are novel, proving their efficacy, reliability, and potentiality. Full article

(This article belongs to the Special Issue Historical Synthetic Polymers: Recent Advances in the Characterization and Preservation of Cultural Heritage)

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27 pages, 85324 KiB

Open AccessArticle

Ageing Effects in Mounting Media of Microscope Slide Samples from Natural History Collections: A Case Study with Canada Balsam and Permount^TM

by Thomas Schmid, Julia Hidde, Sophie Grünier, Robert Jungnickel, Petra Dariz, Jens Riedel and Birger Neuhaus

Polymers 2021, 13(13), 2112; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13132112 - 27 Jun 2021

Cited by 3 | Viewed by 3928

Abstract

Microscope slide collections represent extremely valuable depositories of research material in a natural history, forensic, veterinary, and medical context. Unfortunately, most mounting media of these slides deteriorate over time, with the reason for this not yet understood at all. In this study, Raman [...] Read more.

Microscope slide collections represent extremely valuable depositories of research material in a natural history, forensic, veterinary, and medical context. Unfortunately, most mounting media of these slides deteriorate over time, with the reason for this not yet understood at all. In this study, Raman spectroscopy, ultraviolet–visible (UV–Vis) spectroscopy, and different types of light microscopy were used to investigate the ageing behaviour of naturally aged slides from museum collections and the experimentally aged media of Canada balsam and Permount™, representing a natural and a synthetic resin, respectively, with both being based on mixtures of various terpenes. Whereas Canada balsam clearly revealed chemical ageing processes, visible as increasing colouration, Permount™ showed physical deterioration recognisable by the increasing number of cracks, which even often impacted a mounted specimen. Noticeable changes to the chemical and physical properties of these mounting media take decades in the case of Canada balsam but just a few years in the case of Permount™. Our results question whether or not Canada balsam should really be regarded as a mounting medium that lasts for centuries, if its increasing degree of polymerisation can lead to a mount which is no longer restorable. Full article

(This article belongs to the Special Issue Historical Synthetic Polymers: Recent Advances in the Characterization and Preservation of Cultural Heritage)

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28 pages, 5014 KiB

Open AccessArticle

What about Phenol Formaldehyde (PF) Foam in Modern-Contemporary Art? Insights into the Unaged and Naturally Aged Material by a Multi-Analytical Approach

by Valentina Pintus, Anna Piccolo, Wilfried Vetter, Ligia Maria Moretto, Katja Sterflinger and Manfred Schreiner

Polymers 2021, 13(12), 1964; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13121964 - 14 Jun 2021

Cited by 2 | Viewed by 4771

Abstract

The ageing behavior of phenol formaldehyde (PF) foam, a material increasingly used in modern-contemporary art, was investigated by a multi-analytical approach. PF foams with open- and closed-cell structures were selected and analyzed in their unaged and naturally indoor-aged state by employing optical microscopy [...] Read more.

The ageing behavior of phenol formaldehyde (PF) foam, a material increasingly used in modern-contemporary art, was investigated by a multi-analytical approach. PF foams with open- and closed-cell structures were selected and analyzed in their unaged and naturally indoor-aged state by employing optical microscopy (OM) and fiber optical reflectance spectroscopy (FORS) for assessing their morphology and color alteration. Micro-Fourier transform infrared spectroscopy (μ-FTIR) was used for determining chemical changes and oxidation processes, and the acidity was monitored by pH measurements. The results clearly showed the extreme sensitivity of both open- and closed-cell PF foams to conditions typically found in indoor museums. OM indicated that the cells of the foams are prone to disrupt, and a tendency towards a red color shift was observed with FORS. μ-FTIR revealed the formation of quinone groups resulting from oxidation reactions. Finally, a slight decrease in the acidity was found by pH measurements. Full article

(This article belongs to the Special Issue Historical Synthetic Polymers: Recent Advances in the Characterization and Preservation of Cultural Heritage)

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17 pages, 5144 KiB

Open AccessArticle

The Effect of Pollutant Gases on Surfactant Migration in Acrylic Emulsion Films: A Comparative Study and Preliminary Evaluation of Surface Cleaning

by Laura Pagnin, Rita Wiesinger, Ayse Nur Koyun and Manfred Schreiner

Polymers 2021, 13(12), 1941; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13121941 - 11 Jun 2021

Cited by 2 | Viewed by 2101

Abstract

From their first employment in the 1950s, acrylic emulsions have remained widely used as art material today. Although under certain deteriorating conditions they are very stable, if exposed to high humidity and atmospheric pollutant gases, their structural and chemical conformation is strongly affected. [...] Read more.

From their first employment in the 1950s, acrylic emulsions have remained widely used as art material today. Although under certain deteriorating conditions they are very stable, if exposed to high humidity and atmospheric pollutant gases, their structural and chemical conformation is strongly affected. Dealing with the resulting surfactant migration, various cleaning treatments were considered over the years. However, their choice remains difficult as they easily alter the acrylic component, especially if in contact with aqueous solutions. The present study focuses on investigating the stability of acrylic emulsion films exposed to accelerated aging by various pollutant gases. Firstly, a comparative analytical study was carried out in order to morphologically (by 3D optical and Atomic Force Microscopy) and chemically (by Raman and Infrared spectroscopy) characterize the reactions and degradation products. Subsequently, two water-based cleaning treatments were tested, and a preliminary evaluation of their cleaning effectiveness was performed. The results show that the reaction of atmospheric gas pollutants with water molecules in moisture leads to acidic reaction products that attack the acrylic matrix and favor the migration of the surfactant to the surface. The effectiveness of cleaning treatments depends on the aging conditions applied, which further lead to different surface morphological changes. Full article

(This article belongs to the Special Issue Historical Synthetic Polymers: Recent Advances in the Characterization and Preservation of Cultural Heritage)

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Review

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22 pages, 3126 KiB

Open AccessEditor’s ChoiceReview

What Fate for Plastics in Artworks? An Overview of Their Identification and Degradative Behaviour

by Massimo Lazzari and Daniela Reggio

Polymers 2021, 13(6), 883; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13060883 - 13 Mar 2021

Cited by 9 | Viewed by 3710

Abstract

This review is conceived as a guide for material science researchers and conservators aiming to face the problem of deterioration of contemporary artworks entirely or partially made of plastics. It initially illustrates the analytical approaches for identifying polymeric material components in 3D art [...] Read more.

This review is conceived as a guide for material science researchers and conservators aiming to face the problem of deterioration of contemporary artworks entirely or partially made of plastics. It initially illustrates the analytical approaches for identifying polymeric material components in 3D art objects, such as sculptures and installations, and provides a perspective of their limits and advantages. Subsequently, the methodologies used for studying the deterioration of contemporary art plastics are reviewed, emphasising the main effects of the different types of degradation (i.e., migration of additives, oxidation and hydrolysis) and suggesting the appropriate techniques for their detection. Finally, the application of artificial ageing tests is critically assessed. All the concepts are elaborated through case studies and examples. Full article

(This article belongs to the Special Issue Historical Synthetic Polymers: Recent Advances in the Characterization and Preservation of Cultural Heritage)

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