Change search
Link to record
Permanent link

Direct link
Publications (10 of 49) Show all publications
Jakubowicz, I., Enebro, J. & Yarahmadi, N. (2021). Challenges in the search for nanoplastics in the environment—A critical review from the polymer science perspective. Polymer testing, 93, Article ID 106953.
Open this publication in new window or tab >>Challenges in the search for nanoplastics in the environment—A critical review from the polymer science perspective
2021 (English)In: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 93, article id 106953Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Elsevier Ltd, 2021
Keywords
Analytical methods, Detection, Environmental degradation, Nanoplastics, Sampling, Biology, Detection methods, Environmental matrixes, Modern instrumentation, Nanoscale particles, Natural environments, Sample preparation, Scientific literature, Separation and identification, Mass spectrometry
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-50929 (URN)10.1016/j.polymertesting.2020.106953 (DOI)2-s2.0-85096197728 (Scopus ID)
Note

Funding details: Naturvårdsverket; Funding details: Naturvårdsverket, NV-06511-19; Funding text 1: The authors are grateful to the Swedish Environmental Protection Agency (Naturvårdsverket) , grant ID NV-06511-19 for financial support.

Available from: 2020-12-02 Created: 2020-12-02 Last updated: 2023-05-26Bibliographically approved
Vega, A., Yarahmadi, N. & Jakubowicz, I. (2021). Cyclic axial loads and thermal ageing of district heating pipes. Paper presented at 17th International Symposium on District Heating and Cooling, Nottingham Trent University, DHC2021, 6–9 September 2021, Nottingham, United Kingdom. Energy Reports, 7, 105-109
Open this publication in new window or tab >>Cyclic axial loads and thermal ageing of district heating pipes
2021 (English)In: Energy Reports, E-ISSN 2352-4847, Vol. 7, p. 105-109Article in journal (Refereed) Published
Abstract [en]

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.

Keywords
Polyurethane, Foam, District heating, Mechanical stress, Thermal ageing
National Category
Building Technologies
Identifiers
urn:nbn:se:ri:diva-58165 (URN)10.1016/j.egyr.2021.09.033 (DOI)
Conference
17th International Symposium on District Heating and Cooling, Nottingham Trent University, DHC2021, 6–9 September 2021, Nottingham, United Kingdom
Available from: 2022-01-14 Created: 2022-01-14 Last updated: 2023-05-26Bibliographically approved
Banushi, G., Vega, A., Weidlich, I., Yarahmadi, N., Kim, J., Jakubowicz, I. & Sällström, J. H. (2021). Durability of District Heating Pipelines Exposed to Thermal Aging and Cyclic Operational Loads. Journal of Pipeline Systems Engineering and Practice, 12(1), Article ID 04020067.
Open this publication in new window or tab >>Durability of District Heating Pipelines Exposed to Thermal Aging and Cyclic Operational Loads
Show others...
2021 (English)In: Journal of Pipeline Systems Engineering and Practice, ISSN 1949-1190, Vol. 12, no 1, article id 04020067Article in journal (Refereed) Published
Abstract [en]

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. 

Place, publisher, year, edition, pages
American Society of Civil Engineers (ASCE), 2021
Keywords
Accumulated damage, Foam aging, Fourth generation district heating system, Pipeline durability, Shear tests, 4G mobile communication systems, Adhesives, Deterioration, District heating, Durability, Energy efficiency, Systems engineering, Temperature, Thermal aging, Thermal fatigue, Accelerated aging test, Cyclic mechanical loading, District heating networks, Experimental procedure, Operating temperature, Operation temperature, Residual shear strength, Shear strength tests, Pipelines
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-51889 (URN)10.1061/(ASCE)PS.1949-1204.0000521 (DOI)2-s2.0-85096038490 (Scopus ID)
Note

Funding text 1: The work presented herein is part of the research project “Effects of loads on asset management of the 4th generation district heating networks” funded by the International Energy Agency Technology Collaboration Programme on District Heating and Cooling including Combined Heat and Power (IEA DHC), that is greatly acknowledged. The authors would like to thank Prof. Thorsten Urbaneck from the Department of Mechanical Engineering at the Chemnitz University of Technology, and Mr. Thomas Göschel from inetz GmbH, for providing helpful guidance and information on the collected temperature data from 4GDH. Thanks are extended to Powerpipe Systems AB, Gothenburg Energy, Hafslund Varme AS, Jönköping Energy AB, Vattenfall AB, for the valuable discussions, manufacturing of pipes and support ideas. Moreover, the authors would like acknowledge the colleagues at RISE, especially Mr. Anders Persson for helping on experimental set up. Thanks are extended to Mr. Eun Sick Kang from the Pipeteckorea Co. Ltd., for the cooperation in the axial shear strength test of naturally aged pipes in Korea.

Available from: 2021-01-19 Created: 2021-01-19 Last updated: 2023-05-26Bibliographically approved
Vega, A., Yarahmadi, N. & Jakubowicz, I. (2020). Determining the useful life of district heating pipes: Correlation between natural and accelerated ageing. Polymer degradation and stability, 175, Article ID 109117.
Open this publication in new window or tab >>Determining the useful life of district heating pipes: Correlation between natural and accelerated ageing
2020 (English)In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 175, article id 109117Article in journal (Refereed) Published
Abstract [en]

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. 

Place, publisher, year, edition, pages
Elsevier Ltd, 2020
Keywords
Accelerated ageing, Adhesion strength, Degradation, District heating pipes, Lifetime prediction, Natural ageing, Polyurethane foam, Adhesion, Bond strength (materials), Deterioration, Forecasting, Fourier transform infrared spectroscopy, Polyurethanes, Rigid foamed plastics, Structure (composition), Temperature, Arrhenius relationship, District heating system, Natural and accelerated ageing, New Generation networks, District heating
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-44447 (URN)10.1016/j.polymdegradstab.2020.109117 (DOI)2-s2.0-85081137520 (Scopus ID)
Note

Funding details: Energimyndigheten; Funding details: Vattenfall;

Funding text 1: The authors would like to thank Powerpipe Systems AB, Göteborg Energi, Hafslund Varme AS, Jönköping Energi AB, Vattenfall AB, Borås Energi och Miljö AB, Tekniska Verken i Linköping AB, Kraftringen Energi AB, Energimyndigheten, Energiföretagen Sverige and Swedenergy AB for valuable discussions, manufacturing of pipes and economic support.

Available from: 2020-03-17 Created: 2020-03-17 Last updated: 2023-05-26Bibliographically approved
Karlsson, T. M., Hassellöv, M. & Jakubowicz, I. (2018). Influence of thermooxidative degradation on the in situ fate of polyethylene in temperate coastal waters. Marine Pollution Bulletin, 135, 187-194
Open this publication in new window or tab >>Influence of thermooxidative degradation on the in situ fate of polyethylene in temperate coastal waters
2018 (English)In: Marine Pollution Bulletin, ISSN 0025-326X, E-ISSN 1879-3363, Vol. 135, p. 187-194Article in journal (Refereed) Published
Abstract [en]

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.

Keywords
Fate, FTIR, In situ degradation, Microplastics, Plastic pollution, Weathering
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-34361 (URN)10.1016/j.marpolbul.2018.07.015 (DOI)2-s2.0-85049738270 (Scopus ID)
Note

Funding details: Swedish Environmental Research Council Formas 2014-1146 , and the Interreg project Clean Coastline

Available from: 2018-08-07 Created: 2018-08-07 Last updated: 2023-05-19Bibliographically approved
Vega, A., Yarahmadi, N. & Jakubowicz, I. (2018). Optimal conditions for accelerated thermal ageing of district heating pipes. Paper presented at 16th International Symposium on District Heating and Cooling, DHC 2018, 9 September 2018 through 12 September 2018. Energy Procedia, 149, 79-83
Open this publication in new window or tab >>Optimal conditions for accelerated thermal ageing of district heating pipes
2018 (English)In: Energy Procedia, ISSN 1876-6102, Vol. 149, p. 79-83Article in journal (Refereed) Published
Abstract [en]

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

Keywords
accelerated ageing, Degradation mechanisms, district heating pipes, rigid polyurethane foam, Chemical analysis, Degradation, District heating, Testing, Thermal aging, Accelerated ageing tests, Arrhenius relationship, Degradation mechanism, Degradation patterns, Elevated temperature, Natural degradation, Rigid polyurethane foams, Thermal conductivity
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-35890 (URN)10.1016/j.egypro.2018.08.171 (DOI)2-s2.0-85054082825 (Scopus ID)
Conference
16th International Symposium on District Heating and Cooling, DHC 2018, 9 September 2018 through 12 September 2018
Available from: 2018-11-07 Created: 2018-11-07 Last updated: 2023-08-28Bibliographically approved
Petersen, H., Jakubowicz, I., Enebro, J. & Yarahmadi, N. (2018). Solid-state organo-modification of montmorillonite for manufacturing of plasticized poly(vinyl chloride) nanocomposites. Journal of Vinyl and Additive Technology, 24, E146-E153
Open this publication in new window or tab >>Solid-state organo-modification of montmorillonite for manufacturing of plasticized poly(vinyl chloride) nanocomposites
2018 (English)In: Journal of Vinyl and Additive Technology, ISSN 1083-5601, Vol. 24, p. E146-E153Article in journal (Refereed) Published
Abstract [en]

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.

Keywords
Chlorine compounds, Clay minerals, Nanocomposites, Plastic products, Solvents, Thermodynamic stability, Diisononyl phthalate, Liquid solids, Melt processing, Mixed-metals, Montmorillonite (MMT), Organic modifier, Plasticized PVC, PVC composites, Polyvinyl chlorides
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-34447 (URN)10.1002/vnl.21618 (DOI)2-s2.0-85047858086 (Scopus ID)
Available from: 2018-08-09 Created: 2018-08-09 Last updated: 2023-05-26Bibliographically approved
Yarahmadi, N., Vega, A. & Jakubowicz, I. (2017). Accelerated ageing and degradation characteristics of rigidpolyurethane foam. Polymer degradation and stability, 138, 192-200
Open this publication in new window or tab >>Accelerated ageing and degradation characteristics of rigidpolyurethane foam
2017 (English)In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 138, p. 192-200Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
District heating pipe, Polyurathane foam
National Category
Engineering and Technology
Identifiers
urn:nbn:se:ri:diva-29740 (URN)10.1016/j.polymdegradstab.2017.03.012 (DOI)2-s2.0-85015397049 (Scopus ID)
Projects
Livslängd för Fjärrvärmerör-Fas 1
Funder
Swedish Energy Agency, 39649-1
Available from: 2017-05-30 Created: 2017-05-30 Last updated: 2023-05-26Bibliographically approved
Yarahmadi, N., Vega, A. & Jakubowicz, I. (2017). Determination of essential parameters influencing service life time of polyurethane insulation in district heating pipes. In: Energy Procedia: . Paper presented at 15th International Symposium on District Heating and Cooling, DHC15-2016, 4 September 2016 through 7 September 2016 (pp. 320-323). Elsevier Ltd
Open this publication in new window or tab >>Determination of essential parameters influencing service life time of polyurethane insulation in district heating pipes
2017 (English)In: Energy Procedia, Elsevier Ltd , 2017, p. 320-323Conference paper, Published paper (Refereed)
Abstract [en]

Pre-insulated district heating pipes (DHP) have been in use during the last forty years. Many improvements and development have been done in the system. However, life-time prediction is still an uncertain issue. This paper is a part of a bigger project with the objective to determine mechanisms related to the deterioration of the mechanical and insulation properties of pre-insulated heating pipes as a result of ageing. The focus in this project is on degradation mechanisms of the PUR material at high temperatures. In this paper some results of the two types of exposure are presented. The first type comprises a condition where the new pipes are subjected to accelerated ageing at three different temperatures. The second type comprises condition, when the PUR material itself is aged in different atmospheres in order to identify different degradation mechanisms. The chosen ageing temperatures in the first condition were 130°C, (close to the supply temperature), 150°C and 170°C, (accelerated ageing temperature in EN 253 [1]). Changes in thermal insulation and the adhesion force between the PUR and the steel pipe were evaluated using the transient plane source (TPS) technique and the SP plug method respectively. The results of ageing show that the degradation of PUR is a multi-stage process composed of a rapid change in properties followed by a plateau phase which changes later to a gradual deterioration of the properties. The results of the PUR material exposure at 150°C in air and in nitrogen showed significant differences in the degradation characteristics between the two environments as were revealed by DSC and FTIR methods. © 2017 The Authors. Published by Elsevier Ltd.

Place, publisher, year, edition, pages
Elsevier Ltd, 2017
Keywords
Accelerated ageing, District heating pipe, Life time prediction, Polyurethane insulation, PUR degradation, Degradation, Deterioration, District heating, Heating, Insulation, Polyurethanes, Degradation characteristics, Degradation mechanism, Insulation property, Lifetime prediction, Supply temperatures, Transient plane source techniques, Thermal insulation
National Category
Other Civil Engineering
Identifiers
urn:nbn:se:ri:diva-38110 (URN)10.1016/j.egypro.2017.05.078 (DOI)2-s2.0-85028586584 (Scopus ID)
Conference
15th International Symposium on District Heating and Cooling, DHC15-2016, 4 September 2016 through 7 September 2016
Available from: 2019-03-08 Created: 2019-03-08 Last updated: 2023-05-26Bibliographically approved
Yarahmadi, N., Vega, A. & Jakubowicz, I. (2017). Livslängd för fjärrvärmerör: Fas 1 - Nedbrytningsmekanismer. Stockholm: Energiforsk AB
Open this publication in new window or tab >>Livslängd för fjärrvärmerör: Fas 1 - Nedbrytningsmekanismer
2017 (Swedish)Report (Other academic)
Abstract [sv]

Dagens standard för prefabricerade fjärrvärmerör SS-EN253 innehåller olika testmetoder och krav där ett av de viktigaste är kravet på livslängd på minst 30 år vid en kontinuerlig driftstemperatur på 120 °C. Bestämningen av tekniska livslängden är baserad på mätningar av förändringar i skjuvhållfastheten efter accelererad termisk åldring. Den beräknade livslängden för ett fjärrvärmerör är baserad på extrapolering med hjälp av Arrhenius ekvation. Det finns en stor enighet kring uppfattningen att Arrhenius modellen inte ger en god överensstämmelse med de observerade åldringsdata och att det följaktligen saknas tillförlitliga metoder för livslängdsbestämning av fjärrvärmerör. Trots många forskningsrapporter finns det fortfarande skilda teorier om hur snabbt PUR-isoleringar bryts ner och vilka nedbrytningsmekanismer som dominerar. Syftet med det här projektet är att kartlägga de komplicerade sambanden och förstå vilka nedbrytningsprocesser som dominerar under olika betingelser och utifrån denna kunskap utveckla tillförlitliga metoder för livslängdsprediktering.

Allt testmaterial utgjordes i denna studie av polyuretan (PUR) cellplastisolering som togs ut från nytillverkade fjärrvärmerör. Accelererad åldring genomfördes i luft och i kväveatmosfär vid 150 °C för upp till 8 veckor. Det visade sig att exponering i kväveatmosfär inte orsakar någon mätbar förändring av egenskaper. En motsvarande åldring i luft orsakar däremot stora förändringar i både dimensioner, viktförlust och färg. IR (infraröd) analys kunde också bekräfta att materialet bryts ner genom termo-oxidativa processer. Termo-oxidativ nedbrytning syns också i analyser av cellgassammansättningen. Materialet efter åldring i luft innehåller betydligt mindre halt cyklopentan samtidigt som fyra nya flyktiga ämnen kunde detekteras. Trots alla indikationer på materialets termo-oxidativa nedbrytning har böjhållfastheten inte förändrats hos materialet. Detta måste utredas vidare för att kunna förklara mekanismer bakom resultatet.

Förutom beständighetsstudier av PUR materialet genomfördes långtidsåldring av fjärrvärmerör vid olika temperaturer. Resultaten av skjuvhållfasthet mätningar indikerar att det åtminstone finns tre olika faser i nedbrytningsprocessen. Initialt sjunker hållfastheten troligen på grund av fysikaliska effekter orsakade av de höga temperaturerna. Därefter ökar skjuvhållfastheten troligen beroende på sidoreaktioner och fortsatt tvärbindning. Det tredje steget är en termo-oxidativ nedbrytning som såsmåningom leder till förlust av vidhäftningen. Även värmeledningsförmågan ökar betydligt som ett resultat av nedbrytningsprocesser. Det finns behov av ytterligare forskning för att kunna föreslå en ny modell för livslängdsberäkningar baserade på experimentella resultat.

Place, publisher, year, edition, pages
Stockholm: Energiforsk AB, 2017. p. 32
Keywords
Fjärrvärmerör, nedbrytningsmekanismer, livslängd
National Category
Infrastructure Engineering
Identifiers
urn:nbn:se:ri:diva-29171 (URN)978-91-7673-354-7 (ISBN)
Projects
Fjärrsyn
Available from: 2017-03-31 Created: 2017-03-31 Last updated: 2023-05-26Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-0856-9798

Search in DiVA

Show all publications