Plastics in Heritage Science: Analytical Pyrolysis Techniques Applied to Objects of Design

Abstract

The first synthetic polymers were introduced as constituents of everyday life, design objects, and artworks at the end of the 19th century. Since then, the history of design has been strictly connected with the 20th century evolution of plastic materials. Objects of design from the 20th century are today a precious part of the cultural heritage. They raise specific conservation issues due to the degradation processes affecting synthetic polymer-based plastics. Museums and collections dealing with the conservation of design objects and modern materials need to base their conservation strategies on compositional data that reveal the formulations of historical plastics and their decay processes. Specific and specifically optimized analytical tools are thus needed. We employed flash analytical pyrolysis coupled with gas chromatography and mass spectrometry (Py-GC/MS) and evolved gas analysis coupled with mass spectrometry (EGA-MS) to characterize “historic polymeric materials” (HIPOMS) and heritage plastics at the molecular level with high chemical detail. This approach complements non-invasive spectroscopic diagnosis whenever it fails to obtain significant or complete information on the nature and the state of preservation of the materials under study. We determined the composition of several 20th century design objects (1954–1994) from the Triennale Design Museum of Milan (Triennale Milano - Museo del Design Italiano), which for different morphological, chemical, or physical reasons were unsuitable for characterization by non-invasive spectroscopy. EGA-MS proved capable for the study of the different fractions constituting heterogeneous micro-samples and for gaining an insight into their degradation processes from the contextual interpretation of thermal and mass-spectrometric data.

A Systematic Study on the Degradation Products Generated from Artificially Aged Microplastics

“…The EGA-MS analyses of unaged and artificially aged bulk polymers were performed with an EGA/PY-3030D micro-furnace pyrolyzer (Frontier Laboratories Ltd., Koriyama, Japan) coupled to a 6890 gas chromatograph and a 5973 mass spectrometric detector (Agilent Technologies, Santa Clara, CA, USA). The experimental conditions were the following: temperature ramp for the furnace from 50 °C to 700 °C at 10 °C/min; interface between the pyrolysis furnace and the GC–MS system set at a temperature 100 °C higher than that of the furnace but limited to a maximum of 300 °C; GC injector operated in split mode (20:1 ratio) at 280 °C [ 25 , 26 ]. The evolved pyrolysis products were directly sent to the mass spectrometer using a UADTM-2.5N deactivated stainless-steel capillary tube (3 m × 0.15 mm, Frontier Laboratories Ltd., Japan) held at 300 °C, and using helium (1 mL/min) as the carrier gas.…”

“…The samples (50–100 μg) were placed in deactivated stainless-steel sample cups. Pyrolysis conditions were optimized as follows: pyrolysis temperatures were selected based on the samples analyzed [ 25 , 26 , 27 ]; interface 280 °C; GC injector temperature 280 °C; GC injection operated in split mode with an optimized 10:1 split ratio. The chromatographic separation of the pyrolysis products was performed on a fused silica capillary column HP-5MS (5% diphenyl–95% dimethyl-polysiloxane, 30 m × 0.25 mm internal diameter., 0.25 μm film thickness, J&W Scientific, Agilent Technologies) preceded by a deactivated fused silica pre-column (2 m × 0.32 mm i.d.).…”

Selection of thermal, spectroscopic, spectrometric, and chromatographic methods for characterizing historical celluloid

“…31 The use of EGA-MS and Py-GC/MS, without the addition of TD (thermal desorption), in the context of cultural heritage has increased in recent years, with studies concerning the degradation of organic materials, including plastic artifacts, and identification of their gaseous products. [31][32][33][34][35] Among them, only a few have investigated celluloid objects; Schilling et al 36 have characterized celluloid from the SamCo reference collection with EGA-MS, in the context of the POPART project 37 , while Sutherland et al 10 have investigated a cellulose ester artwork by Naum Gabo with Py-GC/MS. No studies however were encountered in the literature to have coupled Py with TD in the same technique, TD/Py-GC/MS, to study celluloid.…”

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

“…Many synthetic materials are used as coatings and consolidants for the conservation of heritage surfaces [ 9 , 10 , 11 , 12 , 13 ]. Moreover, contemporary collections have large amounts of design objects, furniture and toys constituted by early plastics decaying visibly in museum environments [ 14 , 15 , 16 , 17 ]. Museums condition surveys report that 1% of objects in plastic collections are affected by severe deterioration, and 12% show visible signs of decay [ 17 ].…”