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Bridging the gap - between Science, Industry, Artists and Conservators

More and more modern & contemporary art, applied art objects and furniture are made from plastics and exhibited in museums, public buildings and outdoors...

Nowadays, we see ourselves confronted with the limited durability of these plastics: crumbling, disintegrating, deformation, cracking, delaminating, discolouration and chalking.
The production process of the building blocks of plastics will vary by different producers. Moreover, the manufacturing of art objects, either if it is made by the artist himself or the industry will show difference in material composition due to environmental circumstances during processing.
The degradation process, the rather short service life /museum life and the unfamiliarity with fabrication and maintenance, present some of the problems with plastic objects.
Laboratories in chemical industries, test laboratories at manufacturers and conservation science institutes such as the Instituut Collectie Nederland (ICN) are researching the behaviour and properties of plastics with the aim to solve the above mentioned problems
The results of all these efforts are sometimes hard to consume for conservators or at least as a lack of time, it is difficult to be updated with the latest developments. To overcome this, ICN has set up in collaboration with the Stichting Behoud Moderne kunst; Foundation of the Conservation of Modern Art (SBMK) special materials days. These days are set up as a platform for dissemination of knowledge between scientists, artists, designers and conservators.

This presentation will outline the set-up and the results of special materials days devoted to flexible PUR foams, polyethylene, polypropylene and glass fibre reinforced polyesters and two research projects one on PVC and one PUR elastomers will be presented.

PVC
Scientific research into the composition of the artwork of the Aeromodeller made by Panamarenko, was carried out at the Netherlands Institute of Cultural Heritage (ICN) in Amsterdam, the Netherlands.
The balloon of the artwork is made from old (original) and new patches of poly vinylchloride (PVC).
The adhesive of some patches (repaired places) is very brown/red brown discoloured, while on other repair patches white opaque adhesive is visible. The original adhesive, to be seen in the original seams, has discoloured only to a yellowish colour.
Research has been carried out into the composition of the various types of adhesives present on the balloon and the adhesives that have been selected for the restoration, in order to conserve the artwork.
Research was conducted into the various patches and the original films and also into the amount of softener, still present, in these films.
Furthermore, tests have been performed into the effects of the solvent used for the removal of the old degraded adhesives, on the film and on the adhesive effect of the adhesives.
For the research Fourier Transform Infrared Spectroscopy (FTIR) and Pyrolyse Gas-Chromatography - Mass spectrometry (Py-GCMS) was performed.
Infrared spectra were recorded using a PerkinElmer spectrum 1000 spectrometer combined with a Golden Gate, single Reflection diamond ATR unit.
The research into the composition of the original adhesives resulted in the identification of four different adhesives.
Three of these adhesives that have been detected on the balloon are; an acrylonitril/butadiene rubber adhesive, a white coloured polyurethane/ acryl adhesive and a PVC adhesive.
The adhesives on the PVC film were removed using various solvents and solvent gels.
A fourth adhesive, which was used for repairing the balloon, named Colle de Cologne of the brand Renia, is a neoprene rubber (chloro butadiene) adhesive.
Based on the results of the research a selection of rubber based adhesives could be made which could be used for the restoration.
For the restoration, four rubber adhesives have been selected and submitted to a peel strength test and their applicability was tested. Also, these adhesives were naturally aged under influence of daylight in the laboratory, and artificially light aged in an Atlas Xenotester to induce oxidation.
Cleaning tests and extraction tests were conducted on the PVC films. The results of the extraction tests, cleaning tests, and the natural and artificial light ageing have been reported.
For the repair of small holes and tears a 3MŪ transparent Vinyl Tape 471 was chosen.
Research has been performed into the composition of the adhesive and the carrier of the 3MŪ tape. The carrier of the 3MŪ tape is a copolymer of PVC and PVAC (polyvinyl acetate) and the adhesive is rubber based. The compatibility of this tape and the PVC film was established using the creep test. However, to study the behaviour of PVC film and the tape, experiments were conducted in which PVC film, adhered with the 3MŪ tape, was placed in a heating chamber with changing relative humidity.
Several options to colour PVC-film have been investigated. Coloured varnishes based on Paraloid B72 and the dyestuff Orasol, have been tested. Heat ageing as well as natural and artificial light aging tests has been conducted.

For the re-attachment of the black plastic letters of the balloon, several adhesives were tested. Natural and artificial light- and heat aging tests were performed and finally a 20% solution of Paraloid B72 and ethanol was used.


Pratt chairs and Polyurethane elastomers.

The examination and analytical research of four ‘Pratt chairs’ designed by Gaetano Pesce will be presented. The research was part of the AXA Art Conservation Project in Cooperation with the Vitra Design museum. The design world, the technical development and production and the conservation of the chairs are described. The inherent material properties of polyurethane elastomers, analysis of the materials used in the chairs and the comparison of the researched chairs will explain the condition of the chairs today.

Polyurethane (PUR) elastomers containing the same characteristic elastic property as natural or synthetic rubber were first developed under the trade name Vulkollan in Germany, in the 1940s (Bayer 1963). PUR elastomers are based on the polyaddition reaction products of diisocyanates and polyether or polyester polyols (long-chain diols) and short-chain diols (chain extenders). The rubber-like property is a result of the composition of the segmented building blocks of the polymer; the rigid segment is composed of the diisocyanate and the chain extender, a diol or diamine, whereas the soft segment is composed of the long-chained polyol. Increasing the hard segment, diisocyanate, results in an increase of strength of the polymer.

The four Pratt chairs are part of a series that Gaetano Pesce developed at the Pratt School of Art and Design in New York in 1984. In total Pesce realized four series of Pratt chairs. One series consists of nine Pratt chairs. Each Pratt chair is made of a different hardness of polyurethane elastomer.

To determine the components of the four chairs, samples were taken and examined using Fourier transform infrared (FTIR) spectroscopy. Spectra were recorded using a Perkin Elmer Spectrum 1000 FTIR spectrometer combined with a Golden Gate single reflection diamond ATR unit (sample size 0.6 mm2). Spectra were recorded from 4000 to 600 cm–1. The infrared spectra of the samples were compared with spectra of reference materials.

FTIR showed that three out of the four chairs show weak absorption bands at wavelengths 3320 cm–1 (urethane N–H stretch), weak absorption at 1730–1680 cm–1, (carbonyl C=O) and strong absorption at 1221, 1108 and 1018 cm–1 (C–O–C) which indicates a polyurethane ether type elastomer. The carbonyl stretching region occurring at 1810–1670 cm–1 presents an excellent region from which identification of the particular species may be made.
The amide I band of the urethanes (C=O) occurs at a different frequency from the C=O stretching vibrations of other compounds among such dimers and trimers.
It is not always possible to distinguish individual species in multi-component mixtures because these bands tend to coalesce. Though the building blocks of the polyurethane elastomers used for making the chairs are the same, due to the adding of different amounts of the starting components, crosslinking agents and circumstances during processing the chairs, different types of elastomers are formed, which can be seen in the infrared spectrum at various absorption bands at 1730–1680 cm–1 of biuret and allophanate carbonyl stretching vibrations
To gain insight into the differences of the mechanical properties of the chairs,
Shore hardness of the PUR elastomers of the chairs have been measured using a HPS Durometer (shore A DIN 53505, Hans Schmidt & Co. GmbH, Control In

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