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Enhancing UV-protection of clear coated wood by utilizing reactive UV-absorber and epoxyfunctionalized soybean oil
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This work presents the development of a new pretreatment for clear coated wood, that aims to increase the photoprotection of exterior wood products, and at the same time make the system more environmentally friendly. The pretreatment comprises the reactive UV absorber 2-hydroxy-4(2,3-epoxy­propoxy)-benzophenone (HEPBP), which has a primary epoxy group that can be covalently attached to the hydroxyl groups of the wood substrate. This reactant is accompanied by renewable epoxy functionalized soybean oil (ESBO), which contains a secondary epoxy group that also has the ability to react with the substrate and that promotes the compatibility between the two reactants. The ESBO further seems to have the advantage of increasing the flexibility of the pretreated veneers as well as decreasing the amount of water in the cell wall of the wood. The study was performed in two parts where the first part focused solely on the development and performance of the pretreatment, whereas the second part used the knowledge gained from part one to evaluate the pretreatment in combination with an acrylic clear coating. Grafting reactions were performed on thin wood veneers heated in solvent. In the first part the reaction parameters, temperature and reaction time, were varied to study their effects on the final properties of the pretreatments. The veneers where then analyzed using FTIR to determine if grafting was achieved. Results show that grafting was successful for reactions performed at temperatures above 90 °C. For part two, grafting was successful for both the boil- and dip process, indicating that a considerably shorter reaction time can be used. Samples from both part one and two where then exposed to accelerated ageing and the color change was measured to estimate the UV-resistance. The first part showed improved UV-resistance for some of the pretreatments, whereas the second part was more difficult to evaluate due to the top coat, but a slight improvement can be seen for samples using the pretreatment. A positive result for part two is also that the pretreatment do not appear to affect the adhesion between the substrate and the top coat. It is hence concluded that the proposed pretreatment is a possible way of increasing the photostability of exterior wood.

Abstract [sv]

Detta arbete beskriver utvecklandet av en ny förbehandling för klarlackat trä som syftar till att öka UV-beständigheten av träprodukter för utomhusbruk. Arbetet syftar även till att utveckla systemet till att bli miljövänligare än nuvarande liknande produkter på marknaden. Förbehandlingen utnyttjar primära epoxidgrupper hos den reaktiva UV-absorbenten 2-hydroxy-4(2,3-epoxy­propoxy)-bensofenon (HEPBP) för att skapa kovalenta bindningar till hydroxylgrupper hos träet. Den andra komponenten i systemet är förnyelsebar epoxiderad sojaolja (ESBO) innehållande sekundära epoxidgrupper som även dessa kan binda kovalent till träytan, samt gynna kompatibiliteten mellan de två reaktanterna. Oljan verkar dessutom öka flexibiliteten av förbehandlingen, samtidigt som den minskar mängden vatten som tränger in i cellväggen. Studien utfördes i två delar där den första delen fokuserade enbart på att utveckla förbehandlingen, medan den andra delen utnyttjade information från den första delen för att utvärdera funktionen av förbehandlingen i kombination med en akrylatbaserad klarlack. Ympningsreaktionerna utfördes på tunna träfaner i uppvärmd lösning. I första delen studerades hur temperatur- och reaktionstidsförändringar påverkar den slutgiltiga prestationen av förbehandlingen, och FTIR användes då för att verifiera ympningen. Resultaten visar att ympningen var lyckad för reaktioner utförda vid reaktionstemperaturer över 90 °C. För del två ansågs ympningen lyckad för både dopp- och kokreaktionen, vilket tyder på att betydligt kortare reaktionstider skulle kunna användas. Prover från både del ett och två utsattes sedan för accelererad åldring där färgförändringen av proverna mättes för att uppskatta UV-resistensen av behandlingarna. Första delen visade på ökad UV-beständighet för vissa av behandlingarna. Del två var dock svårare att utvärdera till följd av klarlacken, men en liten förbättring kan noteras för prover som är förbehandlade. En positiv notering från del två är även att adhesionen mellan klarlacken och träytan inte verkar ha påverkats av förbehandlingen. Med detta som grund dras slutsatsen att den föreslagna förbehandlingen kan förbättra UV-resistensen av klarlackat trä för utomhusbruk.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , 47 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2012:17
Keyword [en]
UV-protaction, wood, clear coating, UV absorber, epoxy functionalized soybean oil, grafting
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-92220ISBN: 978-91-7501-292-6 (print)OAI: oai:DiVA.org:kth-92220DiVA: diva2:512753
Presentation
2012-04-27, E3, Osquars backe 14, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Formas, 2008-1447
Note
QC 20120330Available from: 2012-03-30 Created: 2012-03-29 Last updated: 2012-03-30Bibliographically approved
List of papers
1. Grafting of 2-hydroxy-4(2,3-epoxypropoxy)-benzophenone and epoxidized soybean oil to wood: Reaction conditions and effects on the color stability of Scots pine
Open this publication in new window or tab >>Grafting of 2-hydroxy-4(2,3-epoxypropoxy)-benzophenone and epoxidized soybean oil to wood: Reaction conditions and effects on the color stability of Scots pine
2012 (English)In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 97, no 9, 1779-1786 p.Article in journal (Refereed) Published
Abstract [en]

This study investigates the photostabilizing effect of the reactive UV-absorber 2-hydroxy-4(2,3-epoxypropoxy)-benzophenone (HEPBP) when used as a primer for wood. The present work further includes a study on the effect of HEPBP used in combination with an epoxy functionalized vegetable oil as a primer system. The study is based on reactions performed on pine veneers using 3-pentanone as a solvent and 4-(dimethylamino)pyridine (DMAP) as a catalyst, varying the reaction time and temperature. Results from FTIR and SEC measurements indicate that a desired reaction between HEPBP and wood does occur and that there are synergetic effects when HEPBP and oil are combined. Color measurements also indicate that the use of HEPBP and epoxidized soybean oil as pretreatment for wood results in a lower color change after 400 h of artificial weathering. We conclude that using HEPBP in combination with epoxy functionalized soybean oil does improve photostability of wood exposed to artificial weathering.

Keyword
UV-protection, 2-Hydroxy-4(2, 3-epoxypropoxy)-benzophenone (HEPBP), Wood, Epoxy functionalized soybean oil, Grafting
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-92248 (URN)10.1016/j.polymdegradstab.2012.06.006 (DOI)000308051500027 ()2-s2.0-84864606912 (Scopus ID)
Note

QC 20121009. Updated from submitted to published.

Available from: 2012-03-30 Created: 2012-03-30 Last updated: 2017-12-07Bibliographically approved
2. Reactive UV-absorber and epoxy functionalized soybean oil for enhanced UV-protection of clear coated wood
Open this publication in new window or tab >>Reactive UV-absorber and epoxy functionalized soybean oil for enhanced UV-protection of clear coated wood
2014 (English)In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 110, 405-414 p.Article in journal (Refereed) Published
Abstract [en]

The present work investigates the photostabilising effect of a pretreatment consisting of 2-hydroxy-4(2,3-epoxypropoxy)-benzophenone (HEPBP) and epoxy functionalized soybean oil (ESBO), reacted on to Scots pine veneers coated with two different acrylic top coats. Two different pretreatment procedures were used, varying in reaction time and temperature. Results from FTIR and SEC analysis indicate that a large amount of reactant was present on the veneers after treatment with either of the two reaction procedures. Furthermore, coating of the pretreated surfaces was possible and the pretreatment does not seem to affect the adhesion between the coating and the wood substrate. Both accelerated ageing and natural exposure was used to study the resistance to photodegradation, and the results were analysed using colour measurements, FTIR and SEM. These analyses all show that 1400 h of accelerated ageing degrades neither the wood nor the coating to any larger extent. However, after 4000 h of UV exposure some signs of degradation are visible but to a lesser extent for pretreated samples. For the samples exposed to natural weathering during 14 months the performance was good in terms of photostabilisation, however all samples suffer from mould to different extents. Pretreated samples show smaller and more evenly distributed areas of mould compared to the references, which show slightly more mould. The combined coating/pretreatment system is thus assumed to have an effect in terms of photostabilization of the coated wood.

Keyword
2-Hydroxy-4(2, 3-epoxypropoxy)-benzophenone, Epoxy functional vegetable oil, Photodegradation, Soybean oil, UV-protection, Weathering
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-92251 (URN)10.1016/j.polymdegradstab.2014.09.017 (DOI)000347495700047 ()2-s2.0-84949117531 (Scopus ID)
Funder
Swedish Research Council Formas, 2008-1447
Note

Updated from "Manuscript" to "Article". QC 20141121

Available from: 2012-03-30 Created: 2012-03-30 Last updated: 2017-12-07Bibliographically approved

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