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New PhD thesis on Polyurethane Conservation

Wednesday, October 4, 2017 - 11:25

What does the future hold for polyurethane fashion and design? Conservation studies regarding the 1960s and 1970s objects from the MUDE collection

 

Polyurethane (PUR) is one of the most difficult synthetic polymers to preserve. The main aim of this research is to assist PUR condition assessment on historical objects and define storage conditions for this perishable material (20–50 years). According to the current knowledge, PUR continues to degrade even if exposed to controlled conditions (18–21°C, ≈50% RH, in the dark) and following PUR degradation, damage is irreversible. PUR degradation forms include yellowing, crumbling, brittleness and/or chalking, among others. Twenty-four selected PUR-based design and fashion objects (1960s–1970s) from MUDE – Museu do Design e da Moda, Coleção Francisco Capelo (Lisbon) were studied using optical microscopy (visible, UV light) and infrared and Raman microspectroscopies. In this thesis, national and international case studies have been included: foams (ether- and ester based), films (ester-based) and fibres (etherbased); showing fair, poor and unacceptable conditions. Unaged (good condition) and naturally pre-aged references were studied by submitting to natural (outdoor) and artificial (λ˃300 nm) ageing experiments. Based on this approach, different PUR degradation stages are analysed, and visual (micro level) and molecular pathways for PUR natural ageing are suggested. PUR deterioration signs are translated into specific infrared fingerprints (assigned to N–H, C–H and C=O stretching absorptions), and the band at c. 1640 cm-1 (C=Ourea stretching) is proposed as an IR marker for PUR condition assessment. PUR H-bonds (PUR physical crosslinking) are confirmed as liable to natural ageing conditions. To plan a preventive strategy for PUR, a natural ageing experiment (12 months in darkness, 45–55% RH) was carried out for four storage conditions: open air at room T; sealed enclosures at room T, with/without oxygen and at low T (11–13°C). Samples were analysed by colourimetry, gravimetry, contact angle, hardness, optical microscopy, and infrared and Raman microspectroscopies. Further statistical data treatment (ANOVA) was carried out to identify significant variations and to uncover correlations between molecular spectral lines and physical aspects. Raman proved to be a powerful tool in the detection of early stage PUR molecular deterioration and sensitive to molecular changes responsible for yellowing increase. Open-air storage proved to be the most harmful condition, whereas anoxic storage showed the best results. Concerning design and fashion museum objects, also important is a discussion about authenticity as a motor for conservation decisions. From reflections on decision-making for conservation of mass-produced objects, this thesis addresses the question, ‘How to keep what was intended to be temporarily functional?’. A further contribution is a comprehensive biography of PUR fashion and design during the pioneering era.

Susana França de Sá

available at: https://run.unl.pt/handle/10362/23553

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