Novel characterization of decorative coatings using field-flow fractionation and a multi-detector approach

Makan, Ashwell Craig (2017-03)

Thesis (PhD)--Stellenbosch University, 2017.

Thesis

ENGLISH ABSTRACTION: Decorative coatings are present and fulfil and important role in all industry forms from aesthetics, construction, medicine, textiles, manufacturing, packaging and timber. The raw materials used in coatings have an important role to perform and impart various functions, e.g. finishing and feel (gloss or matt), ultraviolet protection against colour fading, resistance against scratches, stains and cracking. Water-based decorative coatings were critically characterized using classical size exclusion chromatography (SEC) and field-flow fractionation (FFF). Various physico-chemical properties were investigated in order to explore potential links between the observed findings and the physical properties of the resultant coating. Particle size of latices and inorganic additives used in decorative coatings were studied using various FFF techniques coupled to an array of detectors, refractive index (RI), dynamic light scattering (DLS), multiangle laser light scattering (MALLS), ultraviolet (UV) and mass spectrometry (MS). Average particle size and particle size distribution from flow FFF (AF4) and sedimentation (SdFFF) had correlations with each other in comparison to DLS. Additional particle populations, which may be due to secondary reactions during synthesis of these particles, could be identified. Mixtures of latex and TiO2 particles were tested with an online AF4 - Inductively Coupled Plasma – Mass Spectrometry (ICP-MS) system to investigate the separation power of AF4. The organic latex particles and the inorganic TiO2 particles could be separated with high resolution using AF4 coupled to UV, MALLS, and ICP-MS. Molar mass, branching and gel-content of latices used in decorative coatings were explored by comparing SEC and AF4. The outcome pointed towards AF4 having more information-rich outcomes compared to SEC. Larger molar masses were observed using AF4 in comparison to SEC. Conformational plots provided more information on branching within acrylic and styrene-acrylic latices as a function of time during free radical polymerization. An interaction study between latices and TiO2 particles using AF4 were conducted to investigate opportunities to minimize TiO2 content in a typical decorative coating formulation. An in-house synthesized sample were compared against a supplier sample focusing on various latex – to – TiO2 ratios, as well as the effect of ultrasonication on the retention time of latex and TiO2 fractograms. Fractionation into narrow fractions and coupling to detection to ICP-MS indicated that the chemical nature of the latex particles as well as the ratio between latex and TiO2 particles has an effect on the overall quantity of the detected TiO2 particles. Furthermore, ultrasonication prior to FFF analyses resulted in latex and TiO2 peaks shifting to earlier retention times, an indication that sonication assist in breaking up large particle agglomerates into smaller and uniform particle populations.

AFRIKAANSE OPSOMMING: Dekoratiewe deklae is teenwoordig en vervul ’n belangrike rol in alle industrieë vanaf dekor, konstruksie, medikasie, tekstiele, vervaardiging, verpakking en houtwese. Die rou materiale wat in deklae gebruik word, speel ʼn sleutelrol om te presteer en om sekere funksies te verrig, bv. afwerking, gevoel, (glans of mat), ultravioletbeskerming teen kleurvervaging, weerstand teen skrape, vlekke en krake. Water-gebaseerde dekoratiewe deklae is krities gekarakteriseer deur gebruik te maak van klassieke grootte-uitsluitingschromatografie (SEC) sowel as veldvloeifraksionering (FFF). Verskeie fisies-chemiese eienskappe is ondersoek om moontlike skakels tussen die genoteerde bevindinge en fisiese eienskappe van die deklae te bewerkstellig. Partikelgrootte van latekspartikels en anorganiese toevoegings in dekoratiewe deklae is bestudeer deur verskillende veldvloeifraksioneringstegnieke gekoppel aan multidetektors bv. brekingsindeks (RI), dinamiese ligverstrooiing (DLS), multihoek-laserligverstrooiingsdetektors (MALLS), ultraviolet (UV) en massa spektroskopie. Gemiddelde partikelgrootte en partikelgrootteverspreiding vanaf vloei-veldvloeifraksionering en sedimentvloeifraksionering het korrelasies getoon in vergelyking met dinamiese ligverstrooiing. Addisionele partikelpopulasies, wat moontlik toegeskryf kan word aan sekondêre reaksies gedurende sintese van hierdie partikels, is geїdentifiseer. Gemengde lateks en titaandioksied (TiO2) partikels is getoets met ʼn aanlyn, onsimmetriese vloei-veldvloeifraksionering (AF4), induksie gekoppelde plasma spektroskopie massa spektrometrie (ICP-MS) sisteem om die skeidingskrag van AF4 te evalueer. Die organiese latekspartikels en die anorganiese TiO2 partikels kon geskei word met hoë resolusie AF4 gekoppel aan UV, MALLS en ICP-MS. Molekulêre massa, vertakking en die gelinhoud van latekse wat gebruik word in dekoratiewe deklae is bestudeer deur SEC sowel as AF4 met mekaar te vergelyk. Die uitkoms het daarop gedui dat AF4 beter resultate gelewer het in vergelyking met SEC; hoër molekulêre massas is gelewer met AF4 in vergelyking met SEC. Grafieke wat die strukturele samestelling aandui, het meer insig verskaf met betrekking tot die vertakking van akrilaat sowel as stireenakrilaat as ʼn funksie van retensietyd gedurende die vrye-radikaalpolimerisasie. ʼn Studie van die interaksie tussen latekse en TiO2 partikels met AF4 is uitgevoer om die moontlike vermindering van TiO2 in ʼn tipiese deklaagformulasie te bestudeer. ʼn In-huis gesintetiseerde monster is getoets teenoor ʼn monster van ʼn verskaffer deur verskillende lateks – tot – TiO2 verhoudings te vergelyk, sowel as die impak van ultrasonikasie op die retensietye van die lateks en TiO2 fraktogramme. Fraksionering in nou fraksies en die koppeling met ICP-MS toon dat die chemiese natuur van die latekspartikels sowel as die verhouding tussen die lateks en TiO2 partikels ʼn rol speel in die hoeveelheid waargeneemde TiO2. Ultrasonikasie gevolg deur FFF analiese het verdergetoon dat die lateks en TiO2 pieke na vroeër retensietye geskuif het; ʼn aanduiding dat sonikasie ʼn rol speel in die opbreking van groot partikelagglomerasies in kleiner, meer uniforme partikelbevolkings.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/101068
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