Polymers and volatiles: Using VOC analysis for the conservation of plastic and rubber objects

There is an acknowledged need for improved conservation of plastic and rubber objects within collections, including improved methods of condition assessment, material identification, and better understanding of material degradation. This reflects the inherent instability and wide-ranging formulations of many such objects and also the relative lack of knowledge in this field. Analysis of volatile organic compounds (VOCs) is a useful method for understanding the chemical processes involved in polymer degradation and for the identification of materials. Conservators and curators have used odor analysis to identify historical plastics for many years, and techniques ranging from acid detection strips to laboratory-based techniques such as solid-phase microextraction-gas chromatography-mass spectrometry have been used to characterize plastic and rubber materials and to understand their degradation. VOC analysis also has potential as a technique for bulk material identification, as a complementary tool to spectroscopic analysis of the surface. A significant advantage of VOC analysis is its potential to be non-invasive, avoiding destructive sampling or even contact with an object. However, there is a greater potential for VOC analysis to be of benefit within conservation than is currently being exploited and significant scope for future research. In fields such as construction or waste management, there is also significant research into analysis of VOC emissions from plastic and rubber materials. The goal of this paper is to systematically review research from a range of fields including conservation, polymer degradation, and plastics recycling and it includes the use of VOC analysis to understand the causes of damage to plastic and rubber objects, to provide evidence of degradation and to monitor degradation progress, and to identify materials and distinguish between different formulations. Summaries of relevant studies are given, and volatile markers of object damage and polymer degradation and key volatile identifiers of a particular material are highlighted

An experimental study of spray foam insulation products - evidence of 1,2-dichloropropane and 1,4-dioxane emissions

An experimental study was conducted using SPME-GC-MS and TD-GC-MS to analyse VOC emissions from three spray foam insulation products. Two closed cell and one open cell materials were tested using SPME-GC-MS passive sampling and a range of VOCs were found with 1,2- dichloropropane (1,2-DCP) found in all products. TD-GC-MS analysis of product 1 (a closed cell foam) and the raw material used for its production (B-side) showed that 1,4-dioxane and 1,2-DCP were both present in the raw material and emitted from the cured foam product. Our findings are currently limited and preliminary, but do seem to indicate that industrial contamination of raw chemicals could be the likely source of these compounds. This could raise the issue of Class 1 and 2B carcinogen VOCs being present in raw polyurethane spray foam insulation (SPF) materials should systematic evidence is provided. As per WHO guidance, it would be a better strategy to remove pollutants at the source. Further research will aim to quantify emission concentrations during application and examine the impact of application strategies

Polyurethane insulation and household products – A systematic review of their impact on indoor environmental quality

We systematically review the impact of polyurethane insulation and polyurethane household products on the indoor environmental quality of buildings. The review breaks down polyurethane products into constituent compounds (isocyanate, polyol, flame retardant, blowing agent and catalyst) as well as secondary emissions, and discusses their implications on human health. Concentrations of compounds emitted from insulation, and household materials, measured in laboratory experiments and case studies are presented in the context of the built environment. We outline that isocyanate exposure over the current legal limits could take place during spray foam insulation application in the absence of personal protection equipment. The study reports that flame retardants are not chemically bound to polyurethane products and they are found in measurable concentrations in indoor environments. Additionally, we provide evidence that catalysts are responsible for at least some negative impact on perceived indoor air quality. More data is required to determine the long-term emissions from spray foam products and the ventilation strategies required to balance energy savings, thermal comfort and good indoor air quality. However, it is not yet possible to determine whether potential health impacts could result from exposure to a single compound or a combination of compounds from spray foam products. We present a risk matrix for polyurethane compounds and propose that flame retardants, by-products, and residual compounds are particularly important for indoor air quality. We conclude by suggesting a framework for further research

Method development for measuring volatile organic compound (VOC) emission rates from spray foam insulation (SPF) and their interrelationship with indoor air quality (IAQ), human health and ventilation strategies

The polyurethane foam industry is projected to reach a worldwide value of up to $74bn by 2022 and with airtightness of new and retrofitted properties continually increasing, an important question arises: what is the impact of these materials on the indoor air quality (IAQ), occupants’ health and indoor environment? As the foams are made in-situ through an exothermic reaction between two chemical mixtures (side A and side B), volatile organic compounds (VOCs) are emitted during their application and curing process. Current research, commercial practices and governmental advice suggests that emissions decrease over time and 8-24 h after application are usually sufficient for residents to return safely to their properties. However, there is still a lack of case studies and a fundamental absence of robust analysis on how ventilation strategies affect long term off-gassing rates and chemical emission quantities. The emission rates from SPF materials could have a direct impact on IAQ if they exceed the occupational exposure rates recommended by NIOSH, or other professional associations. But the difficulty in recording these emission rates is evident as there is still a lack of an international standard for their quantification. To address this issue, we have developed an analytical methodology for measuring some of the composition materials of the foams and residual products associated with their application. The experiment consisted of two stages- active air sampling of spray foam emissions and spiking desorption tubes with a standard solution in order to develop calibration curves. The solution included SPF compounds, or by-products from their application, associated with possible acute impact on health: 1,4 dioxane, chlorobenzene, dibutyltin dilaurate, triethyl phosphate and bis(2-dimethylaminoethyl)ether. We managed to detect five of the chemicals of interest through air sampling and produce calibration curves for 1,4 dioxane, chlorobenzene and triethyl phosphate, which would allow us to quantify the emission rates at the next stage of research. The results of the experiments successfully demonstrated proof of concept quantitative methodology for the compounds of interest. With further research and experiments, this technique has the capacity to be developed into an international standard for measuring VOCs from spray foam emissions and other buildings products. This would provide scientists and industry professionals with the tools to further develop retrofit and ventilation strategies in order to provide healthier buildings

Optical Coherence Tomography for Examination of Parchment Degradation

A novel application of Optical Coherence Tomography utilizing infrared light of 830 nm central wavelength for non invasive examination of the structure of parchment, some covered with iron gall ink, is presented. It is shown that both the parchment and the ink applied are sufficiently transparent to light of this wavelength. In the study, Spectral OCT (SOCT) as well as Polarisation Sensitive OCT (PS-OCT) techniques were used to obtain cross-sectional images of samples of parchment based on scattering properties. The second technique was additionally employed to recover the birefringence properties and the optical axis orientations of the sample. It was shown that freshly produced parchment exhibits a degree of birefringence. However, this property declines with ageing, and samples of old parchment completely depolarise the incident light

Robots can reduce the exposure of people to volatile organic compounds (VOCs) during application of spray foam insulation

An experimental study was conducted to determine whether, and by how much, worker exposure to volatile organic compounds (VOCs) would be reduced when robots are used to apply spray foam insulation. The study was undertaken in a test room where the ventilation rates were controlled and temperature and relative humidity were recorded. Four independent spraying experiments were conducted where robots were used to spray foam onto a suspended timber floor. The environmental conditions were recorded and VOCs were actively sampled using thermal desorption tubes during the periods of spraying (15 min) and curing (10 min). The tubes were analysed using thermal desorption-gas chromatography- mass spectrometry (TD-GC-MS). Four VOCs were quantified in two locations- near the spraying surface and near the worker operating the robot (outside the room). Measurable concentrations of 1,2-dichloropropane, 1,4-dioxane, chlorobenzene and triethyl phosphate (TEP) were quantified inside the room, whilst the concentration near the worker were below the detection limits. The experiment indicates that if workers wear ineffective personal protection equipment, they could be exposed to multiple airborne pollutants due to their close proximity to the spraying surface. Our study is the first to quantify the reduction of workers exposure to four VOCs when robots are used compared to conventional manual spraying

Validation of passive samplers for monitoring of acetic and formic acid in museum environments

Acetic acid and formic acid are volatile pollutants leading to degradation of some heritage materials. They are usually determined in museum environments with various types of passive samplers. In this work, SKC UMEx 200 passive samplers, originally intended for sampling of NO2 and SO2, have been validated for sampling of these organic acids. The sampling rates, extraction efficiency, loss through reverse diffusion or during storage, capacity, and detection limits were determined for both acids. For laboratory exposure, a known concentration of both acids was prepared in a flow-through reactor system at controlled temperature and humidity, the samplers were extracted, followed by analysis using ion chromatography. The sampling rates were determined to be 16.7 ml/min for acetic and 17.7 ml/min for formic acid and the detection limits for 7-day exposure were determined to be 2.1μg/m3 for acetic and 1.9μg/m3 for formic acid. The validated method was finally used for sampling of air in two case studies at the National Museum of Slovenia, where the concentrations in the range of 2–54μg/m3 were determined

Factorial experimentation on photodegradation of historical paper by polychromatic visible radiation

Quantification of the degradation behaviour of heritage objects is essential to manage the rate of degradation and hence optimise their lifetime. In this research, a 23 full factorial experiment was carried out to deepen the understanding of the photodegradation of historical rag paper induced by continuous polychromatic visible radiation. Oxygen concentration, relative humidity and illuminance were investigated as the three environmental factors of primary concern. The effects of these factors on the rate constant of change in diffuse reflectance and tristimulus discolouration were investigated by analysis of variance and multiple linear regression. The three main effects were found to contribute the most to the rate of photodegradation of historical paper, among which relative humidity played the most important role whereas illuminance played the least. This observation is likely to hold when extrapolating the experimental conditions to real conditions in collection storage and display

Effects of NO2 and acetic acid on the stability of historic paper

This research investigates degradation of historic paper in polluted environments during long-term dark storage. In an innovative experiment, degradation rates at realistic pollution levels are compared with degradation rates in the absence of pollution, using a set of real historic papers. The most abundant pollutants in repositories in post-industrial environments are taken into account: acetic acid and nitrogen dioxide. Their action was assessed in terms of reduction of ‘handling’ (as defined by decrease in degree of polymerisation) and ‘display’ (as defined by discolouration) lifetimes. Extrapolations to room conditions enabled lifetime predictions in conditions that are comparable to a real archival or library repository environments while prediction uncertainties were analytically evaluated to assess the significance of conclusions. While 10 ppb of NO2 does reduce the handling lifetime of almost all types of paper, their predicted lifetimes were still assessed to be several millennia, with the exception of acidic paper. Acetic acid at concentrations that are typical for archival and library repositories (<100 ppb) has significantly less effect than NO2 while it does not affect display lifetimes. From a conservation management perspective, it needs to be addressed whether the predicted reductions in otherwise significant handling lifetimes are of real concern and whether air filtration in archival and library repositories is justified

The Development of a SPME-GC/MS Method for the Analysis of VOC Emissions from Historic Plastic and Rubber Materials

Analytical methods have been developed for the analysis of VOC emissions from historic plastic and rubber materials using SPME-GC/MS. Parameters such as analysis temperature, sampling time and choice of SPME fibre coating were investigated and sampling preparation strategies explored, including headspace sampling in vials and in gas sampling bags. The repeatability of the method was evaluated. It was found that a 7 d accumulation time at room temperature, followed by sampling using a DVB/CAR/PDMS fibre, with a sampling time of 60 min at room temperature was a suitable strategy for the detection of VOC emissions from a wide range of historic plastic and rubber artefacts. For 20 mL vials, a sample size of 50 mg was found to be appropriate and grinding the samples improved the repeatability of the analysis and yielded higher levels of emissions. A non-destructive adaptation of the method that could be used directly on historic objects in a museum environment is also presented. The detected emissions improve understanding of ongoing degradation processes within historic plastic and rubber materials, in addition to providing information on material composition