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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Analytical Methods for High Molecular Weight UV Stabilizers / Analytiska metoder för UV-stabilisatorer med hög molekylvikt

Ljungström, Elin January 2022 (has links)
Utomhusprodukter gjorda i plast är sårbara för nedbrytning på grund av UV-energi från solljus. För att stoppa denna fotonedbrytning används UV-stabilisatorer i plastmaterial; en av huvudkategorierna är hindrade aminljusstabilisatorer (HALS, hindered amine light stabilizers). Detta projekt ämnade att utveckla analytiska metoder passande för polymera HALS-föreningar som används i polyolefin-produkter. Huvudfokuset låg på vätskekromatografi med antingen UV eller masspektrometri (MS) detektion. Identifiering lyckades till viss del, extraktion misslyckades, och det gjordes inga kvantifieringsförsök. Detta examensarbete utfördes som ett samarbete mellan KTH och företaget Norner AS. På grund av detta har detaljerna såsom vilka HALS som användes, hur sammansättningen av elueringsgradienter förändrades och masspektrum från MS analys tagits bort eller ändrats till generiska termer. Högpresterande vätskekromatografi (HPLC, high-performance liquid chromatography) med metoden normalfas (normal phase) ansågs vara ett otillfredsställande alternativ på grund av begränsningen av lämpliga lösningsmedel. Både för HPLC och LC-MS-analys användes omvänd fas (reverse phase) med en C18 50 mm kolonn. Gällande HPLC-analys visade sig en våglängd på 240 nm för UV-detektion vara lämplig. För MS-detektion användes positiv elektrosprayjonisering på grund av föreningarnas basiska pKa-värden. Elueringsgradienten med de mest tillfredsställande resultaten var gradientversion 5, med vatten som lösningsmedel A och metanol som lösningsmedel B. En variant av denna gradient användes för LC-MS; gradientversion 5 mod följer samma mönster men med vatten + Y vol% syra som lösningsmedel A, för att möjliggöra jonisering. Additiv UV 2 har låg löslighet i polära lösningsmedel, men genom förtvålning kunde additiv UV 2 lösas i metanol. Med gradientversion 5 mod har förtvålad additiv UV 2 en retentionstid på 1,2 minuter i både HPLC och LC-MS-analys. För HPLC-analys av additiv UV 3 användes gradientversion 5 som resulterade med en retentionstid på 16,8 minuter, och för LC-MS med gradientversion 5 mod 16 minuter. Analys av additiv UV 5 med HPLC gav en retentionstid på 2 minuter med gradientversion 5, och för LC-MS-analys med gradientversion 5 mod var retentionstiden 1,3 minuter. På grund av inkonsekventa resultat mellan HPLC-analyser eller mellan HPLC och LC-MS-resultat kunde inte retentionstid för identifiering av additiven UV 1, UV 4 och UV 6 bestämmas. Extraktion av polymerprover med olika HALS gjordes i toluen vid 80 °C under en timme. I HPLC var det ingen skillnad i kromatogrammen mellan de olika HALS-produkterna. Resultaten från LC-MS stödde resultaten från HPLC, så slutsatsen att extraktionsmetoden inte var framgångsrik drogs. En anledning till detta kan vara att detektionsgränsen i MS och UV överstiger den extraherade halten av HALS. / Outdoor plastic products are vulnerable to degradation due to UV energy from sunlight. To hinder this photodegradation UV stabilizers are used in plastic materials; one of the main categories is hindered amine light stabilizers (HALS). This project aimed to develop analytical methods suitable for polymeric HALS used in polyolefin products. Liquid chromatography was the primary analytical method, with either UV or mass spectrometry (MS) detection. Identification of HALS was partially successful, the attempted extraction was unsuccessful, and there was no attempt at quantification. This thesis was performed as a collaboration between KTH and the company Norner AS. Due to this, the details such as which HALS were used, how the composition of elution gradients changed, and the mass spectrum from MS analysis have been removed or changed to generic terms. The high-performance liquid chromatography (HPLC) method normal phase was deemed as an unsatisfactory option due to the limitation of appropriate solvents. For HPLC and LC-MS analysis reversed phase with a C18 50 mm column was used. In HPLC analysis, a wavelength of 240 nm for UV detection was found to be suitable. For MS detection, positive electrospray ionization was used due to the compounds' basic pKa values. The elution gradient with the most satisfactory results was gradient version 5, with water as solvent A and methanol as solvent B. A variant of this gradient was used for LC-MS; gradient version 5 mod follows the same pattern but with water + Y vol% acid as solvent A, to enable ionization. UV 2 has low solubility in polar solvents, but through saponification UV 2 could be dissolved in methanol. With gradient version 5 mod, saponified UV 2 has a retention time of 1.2 minutes in both HPLC and LC-MS analysis. For HPLC analysis of additive UV 3, gradient version 5 was used which resulted in a retention time of 16.8 minutes, and for LC-MS with gradient version 5 mod 16 minutes. Analysis of UV 5 with HPLC gave a retention time of 2 minutes with gradient version 5, and for LC-MS analysis with gradient version 5 mod the retention time was 1.3 minutes. Due to inconsistency in results between HPLC analysis or between HPLC and LC-MS results, retention time for identification of additives UV 1, UV 4, and UV 6 could not be stated.  Extraction of polymer samples with different HALS was done in toluene at 80 ॰C for one hour. In HPLC, there was no difference in the chromatograms between the different HALS compounds. The results from LC-MS supported the results from HPLC, thus it was concluded that the extraction method was not successful. A reason for this could be that the detection limit in MS and UV might exceed the extracted amounts of the compounds.
2

Photo-oxidative Degradation Of Abs Copolymer

Guzel, Aylin 01 September 2008 (has links) (PDF)
ABSTRACT PHOTO-OXIDATIVE DEGRADATION OF ABS COPOLYMER G&uuml / zel, Aylin M.S., Department of Polymer Science and Technology Supervisor: Prof. Dr. Teoman Tin&ccedil / er Co-Supervisor: Prof. Dr. Cevdet Kaynak September 2009, 55 pages Acrylonitrile-butadiene-styrene (ABS) polymer is one of the most popular copolymer having an elastomeric butadiene phase dispersed in rigid amorphous styrene and semi-crystalline acrylonitrile. Due to double bonds in the polybutadiene phase, ABS copolymers are very sensitive to photo-oxidative degradation. Photo-oxidation of butadiene rubber phase results in the formation of chromorphores and these chromorphores act as initiators in photo-oxidative degradation and after a while ABS starts yellowing. In this work, the relationship between the UV light and the yellowing of ABS samples was also investigated with respect to time. In this study, pure, light stabilized and commercial ABS samples were aged under UV light. As the UV light intensity increased from 800 to 2800 &amp / #61549 / W/cm2, yellowing of the samples were increased for pure ABS. This increase in yellowing of the samples was about 27 times higher compared to lower energy. In this study, UV stabilizers IRGANOX 1076 (sterically hindered phenolic antioxidant), IRGAFOS 168 (hydrolycally stable phosphite stabilizer) and TINUVIN P (hydroxyphenol benzotriazole) were used alone or in combination with each other. Pure ABS samples, commercial ABS samples and UV stabilized ABS samples were aged under the same UV light. UV aging degradation was followed by measuring the yellowness of the samples at certain time intervals. Yellowness of the samples was followed by using Coloreye XTH Spectrometer. Degradation in ABS, however, was followed by using FTIR with an increase in the peak area of carbonyl groups in the ABS matrix. Both color analysis and the FTIR analysis showed that combination of the IRGANOX 1076 and IRGAFOS 168 stabilizers gave the best stabilization. This revealed that combination of phenol and phosphate containing stabilizer is the most useful combination to prevent photo-oxidative degradation of ABS copolymer. Additionally, vegetable oil was applied to the surface of a new set of ABS samples and these samples were aged for 700 h. Yellowing tendency of these samples was compared with the yellowing tendency of ABS samples that are directly aged for 500 h. It was clearly observed that samples with oil smeared had more resistance to UV radiation with respect to others. This shows that oil acts protective layer to the UV light and oxygen and slow down the photo-oxidative degradation. Lastly some commercial ABS samples were compared to each other with respect to their yellowing tendency. Commercial ABS samples coded as K, L, A, B, C and D were aged under UV light at about 500 h. Sample A showed the best resistance against the yellowing among the other commercial ABS samples.

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