Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Hydrophobisation of wood surfaces by combining liquid flame spray (LFS)and plasma treatment: dynamic wetting properties
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden.ORCID iD: 0000-0003-0016-3398
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
SP Technical Research Institute of Sweden.
KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
Show others and affiliations
2016 (English)In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 70, no 6, 527-537 p.Article in journal (Refereed) Published
Abstract [en]

The hydrophilic nature of wood surfaces is a major cause for water uptake and subsequent biological degradation and dimensional changes. In the present paper, a thin transparent superhydrophobic layer on pine veneer surfaces has been created for controlling surface wettability and water repellency. This effect was achieved by means of the liquid flame spray (LFS) technique, in the course of which nanoparticulate titanium dioxide (TiO2) was brought to the surface, followed by plasma polymerisation. Plasma polymerised perfluorohexane (PFH) or hexamethyldisiloxane (HMDSO) were then deposited onto the LFS-treated wood surfaces. The same treatment systems were applied to silicon wafers so as to have well-defined reference surfaces. The dynamic wettability was studied by the multicycle Wilhelmy plate method, resulting in advancing and receding contact angles as well as sorption behaviour of the samples during repeated wetting cycles in water. Atomic force microscopy (AFM) and Xray photoelectron spectroscopy (XPS) were employed to characterise the topography and surface chemical compositions and to elucidate the question how the morphology of the nanoparticles and plasma affect the wetting behaviour. A multi-scale roughness (micro-nano roughness) was found and this enhanced the forced wetting durability via a superhydrophobic effect on the surface, which was stable even after repeated wetting cycles. The hydrophobic effect of this approach was higher compared to that of plasma modified surfaces with their micro-scale modification.

Place, publisher, year, edition, pages
Walter de Gruyter, 2016. Vol. 70, no 6, 527-537 p.
Keyword [en]
contact angle (CA); dynamic wetting, hydrophobisation; hexamethyldisiloxane (HMDSO); liquid flame spray (LFS); multi-scale roughness; nano-sized metal oxide (TiO2); perfluorohexane (PFH); plasma polymerisation; superhydrophobicity; Wilhelmy plate method; wood.
National Category
Wood Science
Research subject
Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-175873DOI: 10.1515/hf-2015-0148ISI: 000376680300006Scopus ID: 2-s2.0-84973442118OAI: oai:DiVA.org:kth-175873DiVA: diva2:862792
Funder
Swedish Research Council Formas, 2014-172
Note

QC 20161101

Available from: 2015-10-23 Created: 2015-10-23 Last updated: 2017-12-01Bibliographically approved
In thesis
1. Wettability of modified wood
Open this publication in new window or tab >>Wettability of modified wood
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Despite many excellent properties of wood which make it suitable for many applications, it suffers from a number of disadvantages limiting its use. For instance, modification is needed to reduce water sorption and to improve decay resistance, dimensional stability and weathering performance. In addition, wood/liquid interaction such as water wettability on wood plays an important role in design and characteristics of many processes and phenomena such as adhesion, coating, waterproofing, wood chemical modification, and weathering. This thesis focuses on enhancing the understanding of wetting of wood, with emphasis on modified wood. The influence of surface chemical composition of wood and its microstructural characteristics on wetting and swelling properties has also been studied.

A multicycle Wilhelmy plate technique has been developed to evaluate wetting properties of porous materials, such as wood, in which the samples were subjected to repeated immersions and withdrawals in a swelling liquid (water) and in a non-swelling liquid (octane). This method was utilized to dynamically investigate contact angle, sorption and swelling properties, as well as dimensional stability of unmodified, chemically and surface modified wood samples. Scots pine sapwood and heartwood samples were utilized to establish the principles of the technique. Acetylated and furfurylated wood samples with different level of modification were thereafter examined utilizing the developed technique for wetting measurements. A perimeter model based on a linear combination of the measured force and final change in sample perimeter was suggested to evaluate the dynamic dimensional stability of wood veneers. The feasibility of this method for studying dynamic wettability was investigated by measuring the changes of advancing and receding contact angles over repeated cycles on surface modified wood samples, created by combining liquid flame spray and plasma polymerisation methods. X-ray photoelectron spectroscopy (XPS) and X-ray computed tomography (XCT) were employed to study the surface chemical composition and microstructural properties of the samples, respectively.

Three different kinetic regimes were observed in the wetting measurements: i) fast wetting and spreading of the liquid on the wood surface, ii) void filling and wicking and iii) swelling, which was the slowest of the three. The multicycle Wilhelmy plate method was found to be suitable for studying liquid penetration, sorption, and dimensional stability of swelling materials. The results demonstrate that the wetting properties of wood are highly affected by surface chemistry and microstructure. It was shown that using both swelling and non-swelling liquids in wetting measurements allow to distinguish between capillary liquid uptake and swelling. Based on this, for chemically modified samples, it was demonstrated that acetylation mostly reduces swelling, while furfurylation reduces both swelling and capillary uptake. This is in line with the microstructural study with X-ray computed tomography where a significant change in the porosity was found as a result of furfurylation, conversely acetylation left the total porosity values unchanged. Wetting results for hydrophobised wood samples demonstrate that the multi-scale roughness obtained by combination of nanoparticle coating and plasma polymerization increased both the hydrophobicity and the forced wetting durability compared to the micro-scale roughness found on wood modified with plasma polymerisation alone.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. 89 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2015:56
Keyword
Wood, dimensional stability, dynamic wettability, surface chemistry, microstructure, swelling, multicycle Wilhelmy plate method, contact angle, sorption, acetylation, furfurylation, surface modification
National Category
Materials Chemistry
Research subject
Chemistry
Identifiers
urn:nbn:se:kth:diva-175875 (URN)978-91-7595-707-4 (ISBN)
Public defence
2015-11-20, Konferencerummet nr 3, SP AB, Drottning Kristinasväg 45, Stockholm, 10:00 (English)
Opponent
Supervisors
Projects
Sustainable wood modification
Note

QC 20151029

Available from: 2015-10-29 Created: 2015-10-23 Last updated: 2015-11-18Bibliographically approved
2. Toward Anti-icing and De-icing Surfaces: Effects of Surface Topography and Temperature
Open this publication in new window or tab >>Toward Anti-icing and De-icing Surfaces: Effects of Surface Topography and Temperature
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Icing severely affects society, especially in the Nordic countries. Iceaccumulation can result in critical performance problems and safetyconcerns for instance in road, air and sea transportation, transmissionlines, marine and offshore structures, wind turbines and heat exchangers.Present active ice-combating approaches possess environmental,efficiency and cost drawbacks. Thus, fabricating icephobic surfaces orcoatings impeding ice formation (anti-icing), but facilitating ice removal(de-icing) is desired. However, different conditions in the environmentduring ice formation and growth add to the complexity of the problem.An icephobic surface that works for a certain application might not be agood candidate for another. These surfaces and the challenges are infocus in this thesis.Wetting properties are important for ice formation on surfaces fromthe liquid phase (often supercooled water), where the water repellency ofthe surfaces could enhance their anti-icing effect. Considering this,different hydrophobic and superhydrophobic surfaces with differentchemistry, morphology and roughness scale were prepared. Since anyinduced wetting state hysteresis on hydrophobic surfaces could influencetheir performance, the wetting stability was investigated. In particulardynamic wetting studies of the hydrophobic surfaces revealed whatsurface characteristics benefit a stable wetting performance. Further, theeffect of temperature, particularly sub-zero temperatures, on the wettingstate of flat and nanostructured hydrophobic surfaces was investigated.This was complemented with studies of the wetting stability of sessilewater droplets on flat to micro- and multi-scale (micro-nano) roughhydrophobic samples in a freeze-thaw cycle. To be consistent with mostapplications, all temperature-controlled experiments were performed inan environmental condition facilitating frost formation. Further, antiicingproperties of hydrophobic surfaces with different topography butsimilar chemistry were studied by freezing delay measurements.A dynamic wetting study using hydrophobic samples with similarchemistry but different topography revealed that multi-scale roughnesscould benefit the wetting stability. However, when these surfaces areutilized at low temperatures the wetting hysteresis observed during acooling/heating cycle is significant. Such a temperature-inducedhysteresis is also significant on superhydrophobic surfaces. I attributethis to condensation followed by frost formation facilitating spreading of 

the supercooled water droplet. The freezing delay measurementsdemonstrate no significant effect of surface topography on anti-icingproperties of hydrophobic surfaces, however the flat surfaces showed thelongest delay. These findings are in agreement with heterogeneous icenucleation theory, suggesting preferential ice nucleation in concave sites,provided they are wetted.In the second part of this thesis, I consider the findings from theprevious part illustrating the limitations of (super)hydrophobic surfaces.The de-icing properties of hydrophilic surfaces with a hydration waterlayer, hypothesized to lubricate the interface with ice, were studied. Heretemperature-controlled shear ice adhesion measurements, down to -25oC, were performed on an adsorbed layer of a polymer, either bottle-brushstructured poly(ethylene oxide) or linear poly(ethylene oxide). The iceadhesion strength was reduced significantly on the bottle-brushstructured polymer layer, specifically at temperatures above -15 oC,whereas less adhesion reduction was observed on the layer formed by thelinear polymer. These findings are consistent with differential scanningcalorimetry (DSC) data, demonstrating that the hydration water, boundto the bottle-brush structured polymer, is in the liquid state at thetemperatures where de-icing benefit is observed. Further, continuingwith the hypothesis of the advantage of surfaces with a natural lubricantlayer for de-icing targets, I studied shear ice adhesion on the molecularlyflat basal plane of hydrophilic mica down to -35 oC. Interestingly, ultralowice adhesion strength was measured on this surface. I relate this to theproposed distinct structure of the first ice-like but fluid water layer onmica, with no free OH groups, followed by more bulk liquid-like layers.This combined with the molecularly smooth nature of mica results in aperfect plane for ice sliding.

Abstract [sv]

Isbildning har en stark inverkan på samhället, speciellt i de nordiskaländerna. Isuppbyggnad kan resultera i kritiska prestandaproblem ochsäkerhetsrisker inom t.ex. väg-, luft-, och sjötransport, kraftledningar,marina- och offshorestrukturer, vindkraftverk och värmeväxlare.Nuvarande aktiva isbekämpningsmetoder uppvisar brister i avseende påmiljö, effektivitet och kostnad. Det finns därmed ett behov av attframställa ytor eller ytbeläggningar som förhindrar isbildning (antiisning)eller underlättar borttagandet av redan bildad is (avisning). Dockkompliceras problemet av de många olika förhållanden under vilka is kanbildas. En beläggning som fungerar för en viss tillämpning behöver intenödvändigtvis vara en bra kandidat för en annan. Dessa ytor ochutmaningar relaterade till dem är i fokus i denna avhandling.Vätningsegenskaper är viktiga för isbildning på ytor från vätskefas(ofta underkylt vatten), och det har visats att vattenavstötande ytor i vissasammanhang kan motverka isbildning. Med detta i åtanke framställdesolika hydrofoba och superhydrofoba ytor, med varierande kemi,morfologi och ytråhet. Eftersom en förändring i de hydrofoba ytornasvätningsegenskaper kan påverka deras funktion studerades vätningsstabilitetenför dessa ytor. I synnerhet dynamiska vätningsstudier av dehydrofoba ytorna avslöjade vilka ytegenskaper som är fördelaktiga förvätningsstabiliteten. Vidare studerades hur temperaturen, särskilt undernoll grader, påverkar vätningstillståndet på släta och nanostruktureradehydrofoba ytor. Arbetet kompletterades med studier av vätningsstabilitetenför vattendroppar på släta samt mikro- och multistrukturerade(mikro-nano) hydrofoba ytor under flera frysningsupptiningscykler.För att vara i linje med de flesta tillämpningar, utfördesalla temperaturkontrollerade mätningar i en miljö där frost kunde bildaspå ytorna. Anti-isegenskaperna hos de hydrofoba ytorna med varierandetopografi men samma kemi studerades vidare genom att studera hur långtid det dröjde innan en vattendroppe på ytan fryste vid en visstemperatur.De dynamiska vätningsstudierna på hydrofoba ytor med samma kemimen olika topografi avslöjade att en ytråhet på flera längdskalor kan haen positiv inverkan på vätningsstabiliteten. När dessa ytor är exponeradeför låga temperaturer är dock vätningshysteresen under en nedkylnings-/uppvärmnings-cykel significant. Den temperatur-inducerade hysteresenär också betydande för superhydrofoba ytor. Detta tillskriver jag 

kondensation på ytan som följs av frostbildning, vilket i sin tur möjliggörspridning av den underkylda vattendroppen på ytan. Mätning avfördröjningen i frysningsförloppet påvisade ingen betydande effekt avyttopografin för hydrofoba ytor, men släta hydrofoba ytor uppvisade denlängsta fördröjningen. Dessa resultat är i överensstämmelse med rådandeheterogen iskärnbildningsteori, som visar på fördelaktig iskärnbildningpå konkava delar av ytan, förutsatt att dessa väts.I den andra delen av avhandlingen utnyttjar jag observationerna frånden första delen vilka illustrerade begränsningarna för superhydrofobaytor, och söker en annan lösning. Avisningsegenskaper för hydrofilastarkt hydratiserade ytor studerades, med hypotesen att hydratiseringkan smörja gränsskiktet med is. Temperatur-kontrolleradeisadhesionsmätningar ned till -25 °C utfördes på adsorberade skikt av enpolymer med många sidokedjor av polyetylenoxid (”bottle-brush”), såvälsom på ett skikt av linjär polyetylenoxid. Isadhesionen blev kraftigtreducerad på ”bottle-brush”-polymeren, speciellt vid temperaturer högreän -15°C. Däremot kunde knappast ingen minskad isadhesion observerasför den linjära polymeren. Dessa observationer överensstämmer meddifferentialskanningskalorimetri (DSC) data, som visar att dethydratiserade vattenskiktet, vilket är bundet till ”bottle-brush”-polymeren, är i vätskeform vid de temperaturer där avisningsfördelar ärobserverade. För att vidare undersöka hypotesen att det vore fördelaktigtmed ett naturligt smörjande skikt på ytan för att uppnå godaavisningsegenskaper, utförde jag isadhesionsmätningar på molekylärtsläta glimmerytor ner till -35 °C. Intressant nog uppmättes extremt lågisadhesion på denna yta. Detta relaterar jag till den föreslagna utprägladehydratiseringsstrukturen, bestående av ett första is-liknande vattenskiktutan fria OH-grupper, följt av ett mer bulkliknande skikt. Detta ikombination med den molekylärt släta naturen hos glimmer resulterar iett perfekt plan för isen att glida på.

Place, publisher, year, edition, pages
Stokcholm: KTH Royal Institute of Technology, 2016. xviii, 80 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2016:11
Keyword
anti-icing, topography, supercooled water, wetting hysteresis, superhydrophobic, contact angle, nucleation, freezing delay, de-icing, ice adhesion, hydration water, liquid-like layer, smooth, lubrication, anti-is, topografi, underkylt vatten, vätningshysteres, superhydrofob, kontaktvinkel, kärnbildning, avisning, isadhesion, hydrerat vatten, vätskeliknande skikt, smörjning
National Category
Chemical Engineering
Research subject
Chemistry
Identifiers
urn:nbn:se:kth:diva-186187 (URN)978-91-7595-901-6 (ISBN)
Public defence
2016-05-27, F3, Lindstedtsvägen 26, KTH Campus, Stockholm, 10:00 (English)
Opponent
Supervisors
Projects
TopNano
Note

QC 20160504

Available from: 2016-05-04 Created: 2016-05-03 Last updated: 2016-05-10Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopus

Authority records BETA

Sedighi Moghaddam, MaziarWålinder, E.P. Magnus

Search in DiVA

By author/editor
Sedighi Moghaddam, MaziarHeydarihamedani, GolrokhFielden, MatthewWålinder, E.P. MagnusClaessson, M. PerSwerin, Agne
By organisation
Surface and Corrosion ScienceNanostructure PhysicsBuilding Materials
In the same journal
Holzforschung
Wood Science

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 245 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf