| 1. |
- Thomas, HS, et al.
(author)
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- 2019
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swepub:Mat__t
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| 2. |
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| 3. |
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| 4. |
- Andersson, Mats R., et al.
(author)
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Improved photoluminescence efficiency of films from conjugated polymers
- 1997
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In: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 85:1-3, s. 1383-1384
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Journal article (peer-reviewed)abstract
- We have demonstrated two general ways to increase the photoluminescence efficiency of films from conjugated polymers. One is to disperse the conjugated polymer on a molecular level by using attractive forces between the conjugated polymer and the matrix. The other method is to substitute the conjugated polymer with side chains which separates the conjugated backbones. Using this idea a new poly(thiophene) with a photoluminescence efficiency of 16% in films has been prepared. LEDs from this polymer exhibit an external efficiency of 0.1% for single layer and 0.7% for double layer diodes.
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| 5. |
- Andersson, Mats R., et al.
(author)
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Electroluminescence from Substituted Poly(thiophenes) : From Blue to Near-Infrared
- 1995
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In: Macromolecules. - : American Chemical Society. - 0024-9297 .- 1520-5835. ; 28:22, s. 7525-7529
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Journal article (peer-reviewed)abstract
- We report a systematic approach to the control of the conjugation length along the poly(thiophene) backbone. The planarity of the main chain can be permanently modified by altering the pattern of substitution and character of the substituents on the poly(thiophene) chain, and the conjugation length is thus modified. We obtain blue, green, orange, red, and near-infrared electroluminescence from four chemically distinct poly(thiophenes). The external quantum efficiencies are in the range of 0.01-0.6%.
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| 6. |
- Andersson, Mats R., et al.
(author)
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Regioselective polymerization of 3-(4-octylphenyl)thiophene with FeCl3
- 1994
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In: Macromolecules. - : American Chemical Society. - 0024-9297 .- 1520-5835. ; 27:22, s. 6503-6506
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Journal article (peer-reviewed)abstract
- We have shown that it is possible to regioselectively polymerize 3-(4-octylphenyl) thiophene with FeCl3. Adding FeCl3 slowly to the monomer leads to a soft and therefore regioselective polymerization. The head-to-tail content was determined by H-1 NMR to be 94 +/- 2%. Thin films of the polymer treated with chloroform vapor have an absorption maximum at 602 nm (2.06 eV) with clear vibronic fine structure. Free standing films have a conductivity of 4 S/cm, which is 100 times higher than for earlier prepared poly(3-(4-octylphenyl)thiophene). A mechanism for the regioregular polymerization is also proposed.
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| 7. |
- Andersson, Mats R., et al.
(author)
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Synthesis of poly(alkylthiophenes) for light-emitting diodes
- 1995
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In: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 71:1-3, s. 2183-2184
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Journal article (peer-reviewed)abstract
- We have demonstrated a general way to tune the emission of poly(alkylthiophenes) by using steric interaction between the repeating units. Light-emitting diodes prepared of the polymers have blue to near-infrared emission.
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| 8. |
- Berggren, Magnus, et al.
(author)
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Controlling inter-chain and intra-chain excitations of a poly(thiophene) derivative in thin films
- 1999
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In: Chemical Physics Letters. - : Elsevier. - 0009-2614 .- 1873-4448. ; 304:1-2, s. 84-90
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Journal article (peer-reviewed)abstract
- The decay of photoexcitations in polythiophene chains has been studied in solid solutions of the polymer from room temperature to 4 K. A strong blue shift of the emission spectrum is observed in the polymer blend, as compared to the homopolymer. Dispersion of the polythiophene suppresses the non-radiative processes, which are suggested to be correlated to close contacts of polymer chains. Quantum chemistry modeling of the excited state distributed on two chains corroborate this conclusion.
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| 9. |
- Berggren, Magnus, et al.
(author)
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Light-emitting diodes with variable colours from polymer blends
- 1994
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In: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 372:6505, s. 444-446
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Journal article (peer-reviewed)abstract
- THE range of materials now available for polymer-based light-emitting diodes (LEDs) is such that electroluminescence can be obtained throughout the visible spectrum(1-12). Here we show that, by blending polymers with different emission and charge-transport characteristics, LEDs can be fabricated in which the emission colour varies as a function of the operating voltage. This phenomenon arises from the self-organizing properties of the blends, in which entropy drives phase separation of the constituent polymers and gives rise to submicrometre-sized domains having a range of compositions and emission characteristics. Emission from domains of different composition is controlled by the ease with which charge is injected, which in turn depends on the applied voltage.
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| 10. |
- Berggren, Magnus, et al.
(author)
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White light from an electroluminescent diode made from poly[3(4‐octylphenyl)‐2,2′‐bithiophene] and an oxadiazole derivative
- 1994
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In: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 76:11, s. 7530-7534
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Journal article (peer-reviewed)abstract
- We report on an electroluminescent diode emitting red, green, and blue light simultaneously. The device is based on a thin polymer layer, poly[3‐(4‐octylphenyl)‐2,2′‐bithiophene] and a thick molecular layer, 2‐(4‐biphenylyl)‐5‐(4‐tertbutyl‐phenyl)1,3,5‐oxadiazole. The quantum efficiency for light conversion is 0.3% and the turn‐on voltage for light emission is 7 V. In this article we present electric and spectroscopic characterizations. A mechanism for the light emission, based on electron and hole recombination between the two organic layers, is proposed
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| 11. |
- Ejlertsson, Jörgen, et al.
(author)
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Effects of co-disposal of wastes containing organic pollutants with municipal solid waste : a landfill simulation reactor study
- 2003
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In: Advances in Environmental Research. - 1093-0191 .- 1093-7927. ; 7:4, s. 949-960
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Journal article (peer-reviewed)abstract
- Different phases of the life cycle of a landfill receiving municipal solid waste (MSW) were monitored in landfill simulation reactors (LSRs) with the aim of investigating the effects of co-disposal of wastes containing organic pollutants (OPs) with MSW. Two LSRs out of four filled with well-characterised MSW received waste materials containing OPs. These included two types of plasticised PVC flooring materials, freon-blown insulation and phosphorus- and nitrogen-based flame-protected materials. Each of the two LSRs was operated under acid fermentative and neutral methanogenic conditions, respectively as were their corresponding controls, i.e. without extra OP. The methanogenic consortia degrading MSW were hampered by the addition of wastes containing OPs, probably due to the presence of Freon R11 and its degradation product, R21. The concentrations of R11 and R21 ranged between 0.1 and 1800 mg m super(-3) depending on the biogas production rate in the OP-amended LSRs. Losses of butylbenzyl- (26%) and bis(2-ethylhexyl)phthalate (15%) from one of two flooring materials was observed, whereas the other remained unaffected. Methanogenic conditions favoured the loss of plasticisers as compared to acidogenic conditions. Total phosphorus was significantly higher in the OP-spiked LSRs, which indicated a transformation of the non-halogenated flame-retardants.
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| 12. |
- Granström, Magnus, et al.
(author)
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Phase separation of conjugated polymers - Tools for new functions in polymer LEDs
- 1997
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In: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 85:1-3, s. 1193-1194
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Journal article (peer-reviewed)abstract
- Within the single family of substituted poly(thiophenes) it is possible to realize such diverse device designs as voltage controlled colours from polymer LEDs, sub-micron size LEDs, and white light emitters. Many of these features become possible by the use of polymer blends in which one or more poly(thiophenes) are mixed with a matrix polymer (PMMA). The phase structure in these blends can be controlled by stoichiometry and mode of formation. That phase structure can be used to prevent exciton transfer, and to define new colours in polymer LEDs. It also allows us to make anisotropic conductors suitable for contacting optical devices.
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| 13. |
- Granström, Magnus, et al.
(author)
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Self organizing polymer films - a route to novel electronic devices based on conjugated polymers
- 1997
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In: Supramolecular science. - : ELSEVIER SCI LTD. - 0968-5677 .- 1873-4146. ; 4:1-2, s. 27-34
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Journal article (peer-reviewed)abstract
- Polymer blends are often used in polymer light emitting diodes as a tool to increase the efficiency of the devices. In this report, we show the necessity to take the phase separation properties of such blends into account, as the miscibility of the involved polymers drastically affects the resulting film structure. By using phase separated polymer blends involving conjugated poly(thiophenes) and different nonconjugated polymers as matrices, different types of applications, such as light emitting diodes with improved voltage control of emitted colour, sub-micron size LEDs and anisotropic conductors are demonstrated. (C) 1997 Elsevier Science Ltd. All rights reserved.
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| 14. |
- Inganäs, Olle, et al.
(author)
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Thiophene polymers in light emitting diodes : Making multicolour devices
- 1995
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In: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 71:1-3, s. 2121-2124
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Journal article (peer-reviewed)abstract
- We can control the bandgap of thiophene polymers over 2 eV by choosing the nature, position and regularity of side chain substitutions. Electroluminescence from these polymers cover the full visible spectrum, from the blue into the near infra-red. Blends of these polymer materials allow us to construct voltage controlled variable colour light sources. A newly developed transfer technique allow us to mount thin oriented films of the polymers in polymer LEDs to obtain polarised light sources giving polarisation anisotropys of up to 3. Sub-lambda light sources have been constructed from these polymer materials using nanometer polymer electrodes.
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| 15. |
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| 16. |
- Nihlstrand, A, et al.
(author)
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Oxygen plasma treatment of thermoplastic polyolefins : Relevance to adhesion
- 1998
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In: Mittal Festschrift on Adhesion Science and Technology. - : VSP International Science Publishers. ; , s. 285-305
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Book chapter (peer-reviewed)abstract
- Injection-moulded plates of four commercial thermoplastic polyolefins (TPOs) were subjected to oxygen plasma treatment. The modified surfaces were analyzed by contact angle measurements and x-ray photoelectron spectroscopy (XPS), and the adhesion properties of the plates were evaluated by a 90° peel test after being lacquered with a two-component polyurethane lacquer. The study included treatments in two different plasma rectors operating at different frequencis. The influence of certain process parameters, such as discharge power, flow rate and gas pressure, was investigated, as was that of frequency (using the same reactor). While the results revealed that oxugen plasma treatment indeed led to improved wettability, the degree of surface modification was not highly affected by changes in the processing conditons. In contrast, there was a great effect on the lacquer adhesion , in particular by changes in discharge power and gas pressure. The results also showed that the TPOs were sensitive in different ways towards changes in the processing conditions. Two of the TPOs revealed good lacquer adhesion for a wide range of processing conditions, while the others were more sensitive. It was also found that, regardless of the absoloute peel force, the failures occured in the substrate at some distance below the oxidized layer. These observations were attributed to a VUV-induced formation of radicals which, in the case of polypropylene-based materials, predominantly lead to B-scissions. As secondary radicals have a higher tendency to form crosslinks that can compensate for chain scission reactions, the difference in the sensitivity of the TPOs was proposed to be related to the amount and distribution of ethylene in the materials.
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| 17. |
- Nihlstrand, A, et al.
(author)
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Plasma polymerization of allyl alcohol on polyolefin-based materials: characterization and adhesion properties
- 1996
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In: Journal of Adhesion Science and Technology. - 0169-4243 .- 1568-5616. ; 10, s. 123-150
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Journal article (peer-reviewed)abstract
- Hydroxyl-rich surfaces have been obtained through the plasma polymerization of allyl alcohol on various polyolefin-based substrates. The influence of plasma parameters (deposition time and power), the type of substrate, and water washing on the chemical structure of the formed plasma polymers was investigated. The characterization involved contact angle measurements, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) analyses. To increase the sensitivity of XPS towards hydroxyl groups, derivatization with trifluoroacetic anhydride was performed. In addition, the adhesion between plasma-polymerized layers and a two-component polyurethane lacquer was evaluated by a 90° peel test. It was shown that power had a pronounced influence on both water wettability and hydroxyl group retention, while deposition time mainly influenced the film thickness. A relationship between the extent of hydroxyl functionality and the loss of material during the washing procedure was also found. Fur thermore, it was shown that the chemical structure of the plasma polymers was not seriously affected by the choice of substrate. On the contrary, the adhesion properties of the substrates with plasma-polymerized layers were found to be highly dependent on the substrate used. For one of the substrates, the adhesion tests revealed an excellent lacquer adhesion when appropriate process parameters during the plasma deposition were used. The other substrate showed considerably lower peel forces. The difference in adhesion properties between the substrates may be explained as an effect of vacuum-ultraviolet (VUV) emission present during the plasma deposition. The VUV emission is able to create radicals in the near-surface region of the substrate and thereby cause chain scission reactions, lowering the cohesive strength of the substrate. Finally, this study showed that reflection absorption spectroscopy (RAS) is a suitable FTIR technique for obtaining structural information about plasma-polymerized layers thinner than 50 nm.
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| 18. |
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| 19. |
- Uvdal, Kajsa, et al.
(author)
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Vapor deposited polyaniline
- 1989
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In: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 29:1, s. 451-456
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Journal article (peer-reviewed)abstract
- We have prepared thin films of polyaniline (emeraldine base) by an open boat evaporation process. These vapor-deposited films have a higher molecular weight than expected from a vapor deposition process, indicating a post deposition chemical process. The films have optical properties very similar to, but not identical to, these of “conventional†emeraldine. After treatment with protonic acid, the films exhibit an electrical conductivity of up to about 10% of that of conventional emeraldine salt.
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| 20. |
- Yu, Wenbin, et al.
(author)
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Antioxidant consumption in squalane and polyethylene exposed to chlorinated aqueous media
- 2012
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In: Polymer degradation and stability. - : Elsevier BV. - 0141-3910 .- 1873-2321. ; 97:11, s. 2370-2377
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Journal article (peer-reviewed)abstract
- Squalane stabilized with 0.2 wt.% of Irganox 1010 and a medium-density polyethylene containing 0.1 wt.% of the same antioxidant were exposed to two different aqueous media (water solutions containing either 10 ppm Cl-2 or 10 ppm ClO2, both buffered to pH = 6.8) at different temperatures between 30 and 70 degrees C. The squalane phase was characterized by differential scanning calorimetry (oxidation induction time, OIT) and infrared spectroscopy, and the aqueous media were analysed after concentrating the analytes using liquid-liquid extraction by liquid chromatography, mass spectrometry and infrared spectroscopy. OIT measurements were carried out on the polyethylene samples after exposure to the chlorinated aqueous media. Exposure of the squalane systems to water containing ClO2 resulted in discolouration by the formation of quinoid structures and a faster depletion of the antioxidant than exposure to water containing Cl-2. The activation energy for the loss of antioxidant activity on exposure to ClO2-water was very low (<10 kJ mol(-1)) in the squalane test (no diffusion control) and 21 +/- 2 kJ mol(-1) at a depth of 1-2 mm from the surface of polyethylene plaques (diffusion control). Calculation from earlier published OIT data from a HDPE exposed to Cl-2-water yielded an activation energy for the loss antioxidant activity of 68 kJ mol(-1). The antioxidant degradation products obtained from the exposure to the ClO2 aqueous medium were found at a higher concentration, were more polar and exhibited a higher proportion of low molar mass species than those obtained after exposure to the Cl-2 aqueous medium. The important chemical difference between ClO2 and Cl-2 is that the former is a one-electron oxidant whereas the latter preferentially reacts by hydrogen substitution. Possible further reactions, in agreement with the observations made, are proposed.
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| 21. |
- Yu, Wenbin, et al.
(author)
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Assessing the Long-term Performance of Polyethylene Stabilised WithPhenolic Antioxidants Exposed to Water Containing Chlorine Dioxide
- 2013
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In: Polymer testing. - : Elsevier BV. - 0142-9418 .- 1873-2348. ; 32:2, s. 359-365
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Journal article (peer-reviewed)abstract
- The addition of chlorine dioxide disinfectant to tap water prevents the spread of infection but has a serious drawback in that it degrades materials used in piping, including pipes made of polyethylene. Efficient methods are required to assess the long-term performance of different combinations of antioxidants and polyethylene grades. We have previously presented a screening method which exposes solutions of phenolic antioxidants in squalane (a liquid, low molar mass analogue of polyethylene) to 70 °C water containing either chlorine dioxide or chlorine. This method assesses the stability of the antioxidants towards these aqueous chlorinated media by determining the oxidation induction time through differential scanning calorimetry. The same experimental set-up with two modifications was used in developing a new method. A 0.3 mm thick polyethylene tape replaced the squalane phase and the supply of fresh water containing chlorine dioxide (10 ppm at pH = 6.8) was continuous; this required minimum attention from the operator over the longer exposure time periods used. Tapes of medium-density polyethylene containing 0.1 wt.% of six different phenolic antioxidants were studied. A linear relationship was established between the times to reach antioxidant depletion in the polyethylene tape samples and the times in the squalane samples (with the same antioxidants at the same concentration). A linear relationship was also found between the initial antioxidant consumption rates in polyethylene and squalane. Infrared spectroscopy and scanning electron microscopy of drawn samples revealed the onset of surface oxidation and surface embrittlement in tape samples exposed beyond the time for antioxidant depletion.
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| 22. |
- Yu, Wenbin, et al.
(author)
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Chlorine dioxide resistance of different phenolic antioxidants in polyethylene
- 2015
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In: Polymer degradation and stability. - : Elsevier BV. - 0141-3910 .- 1873-2321. ; 111, s. 1-6
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Journal article (peer-reviewed)abstract
- A series of polyethylene tape samples containing 8 different phenolic antioxidants (concentration = 0.1 +/- 0.01 wt.%) were exposed to water containing 10 ppm chlorine dioxide buffered to pH = 6.8 at 70 degrees C for different periods of time. The degradation rate and depletion time of the antioxidants in the polyethylene were obtained by oxidation induction time measurements using DSC. The majority of the tape samples (6 out of 8) showed a simple behaviour: the rate of antioxidant loss decreased and the antioxidant depletion time increased in linear fashion with increasing initial molar concentration of phenolic groups in the polymer. The tape that contained Hostanox O3 had a high initial phenolic concentration but it exhibited a short antioxidant depletion time due to the limited solubility of this antioxidant in polyethylene. Tapes containing Irganox 1330 and Cyanox 1790 showed antioxidant depletion times that were almost twice that of the other antioxidants with the same initial molar concentration of phenolic groups.
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| 23. |
- Yu, Wenbin, et al.
(author)
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Deterioration of polyethylene pipes exposed to water containing chlorine dioxide
- 2011
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In: Polymer degradation and stability. - : Elsevier BV. - 0141-3910 .- 1873-2321. ; 96:5, s. 790-797
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Journal article (peer-reviewed)abstract
- Chlorine species used as disinfectants in tap water have a deteriorating effect on many materials including polyethylene. There are only very few scientific reports on the effect on polyethylene pipes of water containing chlorine dioxide. Medium-density polyethylene pipes stabilized with hindered phenol and phosphite antioxidants were pressure tested with water containing 4 ppm chlorine dioxide at 90 degrees C and pH = 6.8 as internal medium. The stabilizers were rapidly consumed towards the inner pipe wall; the rate of consumption was four times greater than in chlorinated water (4 ppm, pH = 6.8) at the same temperature. The depletion of stabilizer occurred far into the pipe wall. A supplementary study on a polymer analogue (squalane) containing the same stabilizer package showed that the consumption of the phenolic antioxidant was 2.5 times faster when exposed water containing chlorine dioxide than on exposure to chlorinated water. The subsequent polymer degradation was an immediate surface reaction. It was confirmed by differential scanning calorimetry, infrared spectroscopy and size exclusion chromatography that in the surface layer which came into contact with the oxidising medium, the amorphous component of the polymer was heavily oxidized leaving a highly crystalline powder with many carboxylic acid chain ends in extended and once-folded chains. Scanning electron microscopy showed that propagation of cracks through the pipe wall was assisted by polymer degradation.
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