This study presents a novel status assessment method for district heating (DH) pipelines in operation, which we call "Pipeopsy"(a biopsy for pipes). The method evaluates adhesion strength between the service pipe and polyurethane (PUR) insulation, which is a crucial property for the durability of DH pipes and the extent of degradation of PUR foam closest to the service pipe. This method is based on three parts: (1) measuring adhesion strength and taking samples of the foam, (2) analyzing the foam in a laboratory using Fourier-transform infrared (FTIR) spectroscopy, and (3) restoring pipeline by replacing the foam and sealing the casing by welding polyethylene plugs in the holes. Temperature dependence and measurement accuracy of the shear strength test method have also been examined, as well as correlation with the standard axial shear strength test method. The shear strength of the aged pipes shows no temperature dependence, while the quotient between the value produced with the plug method and axial method is 3.1. Compared with the standard test methods, the advantages of Pipeopsy involve small cost, less damage to pipes, and the use of simple mobile tools for taking samples and performing measurements. Importantly, testing can be performed without shutting down the operation of DH pipelines. Furthermore, the method provides not only the information on adhesion strength but also information on the extent of chemical degradation in PUR. This combination of information provides a more detailed picture of the status of pipes and can be used to make a prediction about the remaining lifetime. Pipeopsy produces many results in a short time, and better statistics, which provide a solid basis for decision-makers focused on the maintenance of DH pipes or for applying artificial intelligence. 

It is generally recognized that the use of physical and digital information-based solutions for tracking plastic materials along a value chain can favour the transition to a circular economy and help to overcome obstacles. In the near future, traceability and information exchange between all actors in the value chain of the plastics industry will be crucial to establishing more effective recycling systems. Recycling plastics is a complex process that is particularly complicated in the case of acrylonitrile butadiene styrene (ABS) plastic because of its versatility and use in many applications. This literature study is part of a larger EU-funded project with the acronym ABSolEU (Paving the way for an ABS recycling revolution in the EU). One of its goals is to propose a suitable traceability system for ABS products through physical marking with a digital connection to a suitable data-management system to facilitate the circular use of ABS. The aim of this paper is therefore to review and assess the current and future techniques for traceability with a particular focus on their use for ABS plastics as a basis for this proposal. The scientific literature and initiatives are discussed within three technological areas, viz., labelling and traceability systems currently in use, digital data sharing systems and physical marking. The first section includes some examples of systems used commonly today. For data sharing, three digital technologies are discussed, viz., Digital Product Passports, blockchain solutions and certification systems, which identify a product through information that is attached to it and store, share and analyse data throughout the product’s life cycle. Finally, several different methods for physical marking are described and evaluated, including different labels on a product’s surface and the addition of a specific material to a polymer matrix that can be identified at any point in time with the use of a special light source or device. The conclusion from this study is that the most promising data management technology for the near future is blockchain technology, which could be shared by all ABS products. Regarding physical marking, producers must evaluate different options for individual products, using the most appropriate and economical technology for each specific product. It is also important to evaluate what information should be attached to a specific product to meet the needs of all actors in the value chain.

Nanoplastics (NPs), which we define in this paper as solid plastic particles with the size <1 μm, unintentionally produced from the degradation and fragmentation of larger plastic objects are probably the least known area of plastic litter but are suspected to pose the greatest risk to the environment. However, no NPs have been detected in natural environments to date. This review attempts to provide a critical overview from the polymer science perspective of the relevant scientific literature, which could facilitate finding secondary NPs in natural environments. The information on secondary NPs has been scarce due to the big challenges in sampling, separation, and detection of these nanoscale particles. This review highlights the most important challenges and obstacles and discusses the mechanisms of generation of secondary NPs. It provides also a critical overview on modern instrumentation, newly developed workflows, promising techniques for sampling and sample preparation, and detection methods including spectroscopies (Raman and FT-IR), microscopies (SEM and TEM) and mass spectrometry (GC–MS and ToF–SIMS). We conclude that finding NPs in natural environments is plausible yet uncertain, which drives towards the development of a methodology for collection, separation and identification of NPs in environmental matrices along with a thorough evaluation of the process of formation of secondary NPs, their fate and effects on living organisms and the environment. To find nanoplastics in natural environments it is important to know the process of their formation, their fate, and experimental constraints.

Thermal ageing at elevated temperatures is the standard method to determine the service life of pre-insulated district heating pipes nowadays. However, DH pipes are also subjected to axial movements which can affect the adhesion strength between the polyurethane foam and the service pipe. This contact surface is usually exposed to the highest temperatures. In this project, DH pipes were aged at elevated temperatures and at the same time cyclic axial loads were applied. Two DH pipes were only exposed to thermal ageing at 130 and 140 °C, while two other similar pipes were also exposed to cyclic axial loads. The adhesion strength was evaluated as the function of ageing time using the RISE plug method. Any changes in the chemical structure of the PUR samples were also observed using Fourier transform infrared spectroscopy. Comparing the results in this investigation, we found that the degradation of the mechanically loaded pipes was significantly faster than the degradation observed in non-loaded pipes at the same ageing temperatures. The FTIR study revealed that cyclic mechanical loads accelerated the chemical degradation of the PUR foam during thermal ageing. This study shows how important it is to consider all influencing factors in accelerated ageing. The methods presented here should be considered as an alternative to thermal ageing at high temperatures because the combination of mechanical and thermal loads reproduces better the real operating conditions. It is even of bigger interest when energy from different sources will be connected to the fourth generation of DH networks, which can cause more temperature fluctuations.

Fourth generation district heating networks (4GDH) must be designed for future energy systems, integrating renewable volatile energy sources, with lower operation temperatures, and consequent reduction of heat losses and increased energy efficiency. The lower levels of operating temperature and the greater amount of cyclic loading, influence aging, and the service life of 4GDH pipelines, differently from traditional district heating (DH) networks, and thus require proper investigation of the system response at the cross-sectional level. To evaluate the material durability of 4GDH pipelines, we have analyzed the behavior of the service steel pipe, the insulation foam, and their adhesive interaction, using an innovative analytical and experimental procedure. This paper describes the influence of traditional and future operational loading conditions on the performance of preinsulated bonded single-pipe systems, representing the majority of currently operating DH pipelines. The performed fatigue analysis of the steel service pipe showed that the lifetime of 4GDH pipelines is expected to increase because of the lower operating temperature, and the low impact of thermal loading volatility in the network, compared to conventional DH. The accelerated aging tests of DN 50/160 pipes demonstrated that the combined effect of cyclic mechanical loading and thermal aging accelerates the rate of chemical degradation of the PUR foam, leading to a faster deterioration of the mechanical adhesion strength. The shear strength tests of naturally aged DH pipes revealed that, besides the initial pipe system characteristics and aging period, the residual shear strength of the polyurethane (PUR) foam depends on the temperature history, decreasing with the level of operating temperature and amount of fluctuation. The obtained results give a better understanding of the performance of traditional and 4GDH pipelines in operation that need to be appropriately considered in the engineering design standards of DH networks toward a more sustainable and energy-efficient infrastructure. 

District heating (DH) systems constitute a smart and environmentally friendly solution for energy distribution in the heat sector in Europe. This technique is still expanding but already faces some issues such as status assessment of the current DH networks and the development of new generation networks for low-temperature DH. Therefore, it is essential to understand the ageing behaviour of pipes under operating conditions and to find the relevant parameters that control the degradation processes. Many factors affect the deterioration of DH pipes, especially the polyurethane foam, which makes it very complex to find a reliable prediction model. Models based on a linear Arrhenius relationship using results from high ageing temperatures seem to be incorrect. For this study, 10 pipes that have been in service for many years in Sweden and Norway were evaluated. The aim was to study the impact of natural ageing on the mechanical adhesion and chemical structure of the polyurethane foam, which affects the pipe's performance. A test method developed at the Research Institutes of Sweden (RISE), called RISE plug method, was used to study the mechanical adhesion strength. In addition, Fourier transform infrared spectroscopy was used to observe any change in the chemical structure. The results were compared with previous analyses of DH pipes exposed to accelerated ageing. This information helps to provide a better comprehension of the deterioration of the current generation of pre-insulated DH pipes and to improve the accelerated ageing methods used nowadays to predict the technical lifetime of DH pipes. Our results suggest that the lifetime of DH pipes has been underestimated when using artificial ageing at relatively high temperatures. The data collected from naturally aged pipes gave confirmatory information about their physical status compared with our laboratory tests. This study also suggests that infrared analyses could be used as an early indication of the degradation of the polyurethane foam at the interface with a steel pipe. 

Polyethylene is a commonly used polymer in plastic products and is often found as marine litter. Nevertheless there is limited knowledge about what happens to the material when it ends up in the sea. Polyethylene films were therefore thermally oxidised to four different levels of degradation. The films were then placed in stainless-steel cages in the sea off the Swedish west coast for 12 summer weeks. Subsamples were analysed with respect to biofouling, degradation and buoyancy. All levels showed a continued oxidation in the field. The pre-degraded films started fragmenting and the non-degraded films showed a decrease in tensile strain. All levels showed increased biofouling with higher presence of filamentous algae and bryozoans on pre-degraded materials. The density (kg·m−3) of the films was seen to increase slightly, and the apparent density for the pre-degraded films (density of the films with biofilm) showed a strong increase, which resulted in sinking.

Technical lifetime prediction of polymeric materials is often based on accelerated ageing tests at elevated temperatures. Samples are exposed to relatively high temperatures to accelerate the natural degradation processes. For district heating pipes, accelerated thermal ageing is the ordinary method used to determine the lifetime of pipes. According to the Standard EN 253:2009 + A1:2013, the district heating pipes shall be subjected to an accelerated thermal ageing for a long period of time at 160 °C or 170 °C. The lifetime is determined by extrapolation using the Arrhenius relationship. However, papers published recently have questioned this method, especially the high temperatures used for ageing of the pipes and the use of Arrhenius equation to describe the complicated degradation mechanisms, which can result in the erroneous estimation of the technical lifetime. Our investigation has shown the complexity of the pipe's degradation mechanisms. The behaviour of mechanical shear strength at elevated temperatures (T > 130 °C), suggests an alteration rather than an acceleration of the degradation mechanisms. Accelerated ageing tests should reproduce the proper natural ageing mechanisms. The analyses of PUR's thermal conductivity and its chemical structure by FTIR confirmed the degradation patterns

The preparation of poly(vinyl chloride) (PVC) nanocomposites via direct melt processing is still posing problems mainly because of the lack of availability of suitable commercial organoclays and because of the low thermal stability of PVC. A new type of organic compounds for modifying montmorillonite (MMT), which is suitable for use in plasticized PVC, has been found earlier. The current study shows that it is possible to achieve partially exfoliated PVC nanocomposites with greatly improved mechanical properties using a method of liquid-solid–state intercalation of MMT when using tributyl citrate and diisononyl phthalate (DINP) plasticizers as organic modifiers. It is also shown that liquid mixed metal stabilizers have the ability to intercalate the clay at least when DINP is used. The observation raises questions regarding how this phenomenon can affect the thermal stability of PVC composites. J. VINYL ADDIT. TECHNOL., 24:E146–E153, 2018. © 2017 Society of Plastics Engineers.

The urgent need for revision of the normative test method (EN 253) for the lifetime prediction of district

heating pipes requires a better understanding of the failure mechanisms involved. Therefore, various

methods were used to study thermal degradation characteristics of rigid polyurethane (PUR) foam in

both air and nitrogen atmosphere. Accelerated ageing in nitrogen caused insigni

ficant changes, whereas

ageing in air caused signi

ficant changes in weight, dimensions, chemical structure and cell gas composition,

indicating importance of the thermo-oxidative type of degradation. A clear indication of the

thermo-oxidative type of degradation was the formation of new carbonyl groups in PUR together with

the loss of CH

2 groups after ageing in air. Another result of ageing in air was the loss of pentane and

cyclopentane, and the formation of some new volatile compounds in the cells of PUR foam. However,

despite a large difference in degradation characteristics between the samples aged in air and in nitrogen,

no signi

ficant difference in the flexural strength of PUR foam was recorded during the induction stage of

the degradation process. Furthermore, it is shown that the signi

ficant drop in shear strength, which

re

flects the adhesion force between PUR foam and steel pipe, observed during the early stage of

accelerated ageing of district heating pipes is not caused by thermo-oxidative degradation.