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Results of a preliminary model showing change in molecular weight at the surface of a polymeric material with different initial moisture contents.
Contexts in source publication
Context 1
... model was assessed under two scenarios, one referred to as 'Higher moisture' and the other as 'Lower moisture', with initial concentrations of moisture at the surface of the material used as inputs, representing an object exist- ing in an environment with a higher or lower RH respect- ively. Figure 2 shows that the change in molecular weight at the surface proceeds at a greater rate under higher RH conditions, and shows the relative difference in the rates of change. This indicates that under the 'Higher moisture' scenario, an object would crack and/ or become brittle more quickly. ...
Context 2
... experimental results, values for key parameters can be identified and used as inputs for a model that consists of multiple degra- dation processes. Outputs like those shown in Figure 2 could then be used to understand the potential impact of preventive conservation decisions such as RH settings on the degradation of modern polymeric objects in collections. ...
Citations
... As one of the first semi-synthetic plastics produced industrially in the early 20th century and owing to the social impact caused by the advent of polymers, many CA objects, including the sculptures made by Naum Gabo, Antoine Pevsner and László Moholy-Nagy, are collected, conserved and cared for in museum collections and archives, as iconic and valued representations of the past. However, many of these materials present stability issues associated with their chemical and physical degradation, imposing a challenge for conservators in the search for optimal storage and display conditions [5][6][7][8]. ...
As one of the first semi-synthetic plastics produced industrially, cellulose acetate (CA)-based artefacts represent valued items in museum collections and archives which, however, present stability issues. High temperature and relative humidity conditions have long been known to promote changes in CA properties, for instance, due to the deacetylation of CA polymer chains and the loss of plasticiser from the polymer matrix. However, there is a need for improved methods for the quantification of plasticiser loss and CA deacetylation. In this context, this contribution presents a new approach for enabling the investigation of plasticiser loss and deacetylation degradation processes in historic plasticised CA-based artefacts which is based on high-resolution proton nuclear magnetic resonance spectroscopy (¹H NMR). The proposed methods allow for simple and fast quantification of diethyl phthalate contents and average degree of substitution (DS), while requiring no need for extractive separation between the plasticiser and the CA polymer matrix prior to analysis. Both methods are demonstrated by their application towards a series of reference samples, historic artefacts and artificially aged plasticised CA materials. Our analysis indicates that plasticiser content and DS can be accurately quantified by using high-resolution ¹H NMR and both methods have been compared to analyses performed using infrared spectroscopy.
Participatory system dynamics is assumed to generate inter‐ and transdisciplinary understanding and whole‐system perspectives via scripted workshop structure, facilitation, and the use of visual boundary objects. However, there is little research into how exactly workshop activities and facilitators affect communication dynamics during a workshop and create an interdisciplinary perspective. Thus, we offer an innovative dynamic understanding via a rare microlevel analysis of facilitation and dynamics of communication and interdisciplinarity in a group model‐building workshop. We investigate how the conversation focus unfolds over time and examine in depth disciplinary transitions as well as the facilitator's role. We also analyse participants' perceptions of interdisciplinarity from the workshop and provide a research framework for workshop microlevel analysis. Based on the workshop's heritage science setting, we discuss the recursive nature of generating joint meaning and the use of participatory system dynamics for managing interdisciplinarity in a research project and make recommendations. © 2023 The Authors. System Dynamics Review published by John Wiley & Sons Ltd on behalf of System Dynamics Society.
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).
Plastic-focused collection surveys are a fundamental starting point for locating, identifying and assessing the conservation needs of polymer-based objects, and are increasingly conducted internationally. As surveys are both time- and people-intensive, it is critical to ensure the optimal usefulness of the data for the institution and wider conservation community through consistent documentation, using flexible robust data structures, and making results accessible. However, only summaries of survey results have been published in the conservation literature, resulting in a lack of continuity and information dissemination. This is problematic for institutions without the necessary resources to conduct extensive surveys and to identify polymer types. This paper outlines the collaborative development of a plastic-focused collection survey methodology, highlighting the importance of developing and testing standardised procedures, engaging with expert collaborators, and ensuring results are accessible.
