20.500.12556/DKUM-62222 VPLIV PIROGENEGA SiO2 IN Al2O3 NA REOLOŠKE LASTNOSTI PRAŠKASTEGA LAKA INFLUENCE OF PYROGENIC SIO 2 AND AL 2 O 3 ON RHEOLOGICAL PROPERTIES OF POWDER COATING Praškasti lak je, kot že ime pove, sestavljen iz prašnih delcev. Prah je suha trdna snov, sestavljena iz velikega števila finih delcev in ob stresanju prosto teče. Ima lastnosti trdnega materiala, obenem pa tudi lastnosti, podobne tekočinam. Za uspešno nanašanje praškastega laka na objekt mora le-ta dobro teči, kar pomeni, da se ustrezno zmeša z zrakom in fluidizira, obenem pa se mora ob elektrostatskem lakiranju dovolj naelektriti in oprijeti lakiranega objekta. Omenjene lastnosti niso vedno optimalne, zato jih izboljšujemo z dodajanjem različnih dodatkov. V glavnem gre za pirogene nano materiale, ki obdajo delce praškastega laka in delujejo kot mazivo, po mehanizmu, ki je podoben delovanju kroglic v krogličnem ležaju. Pri praktičnem delu v laboratoriju smo pirogeni material s pomočjo mešanja porazdelili med delce praškastega laka. Na površini delcev praškasti lak tvori tanek sloj, ki deluje kot mazivo in omogoča neovirano drsenje delcev drug ob drugem. S poskusi smo skušali ugotoviti optimalni delež različnih fluidizacijskih dodatkov v praškastem laku. Že manjši dodatek precej poveča fluidizacijo in izboljša tečenje prahu. Z nadaljnim dvigovanjem deleža se fluidizacija do določene mere povečuje, nato doseže maksimalno vrednost, nakar se zaradi presežka fluidizacijskega sredstva, ki samo po sebi slabo teče, zopet poslabša. Reološke lastnosti prahu smo določali z reometrom FT4, ki deluje po principu določanja navora, potrebnega za vrtenje rotacijskega telesa. Meritve so bile ponovljive in v veliki meri avtomatizirane. Poleg tega smo pripravljenim vzorcem določali nasipni kot ter opazovali obnašanje prahu pri lakiranju in lastnosti zapečenega praškastega laka. Vzorce prahu smo opazovali tudi s pomočjo elektronskega mikroskopa in tako dobili vpogled v strukturo posameznih materialov. Pomembna je bila tudi granulacijska sestava prahu. Ugotovili smo, da večji delež finih delcev fluidizacijo zaradi velike specifične površine poslabša. Preveč grobi delci potrebujejo več energije za svoje premikanje, kar zopet ne vpliva najbolje na tečenje prahu. Opaziti je bilo tudi razliko med različnimi fluidizacijskimi dodatki, kar izhaja iz njihove različne granualcije, kemijske sestave in površinske obdelave. Powder coating, as the name suggests, consists of powder particles. Powder is a dry bulk solid, composed of very fine particles and can flow freely when poured or shaken. It possesses properties of a solid material as well as properties similar to liquids. For effective application of powder coating on to coated object it should flow well. That means, it should be properly mixed with air and fluidized. During application, powder should accumulate enough electrostatic charge and effectively adhered to the coated object. These properties are not always optimal, so we need to improve them by adding various additives. Basically, they consists of nanoscale materials that surround the particles of powder coating and act as a lubricant, with mechanism similar to the functioning of the balls in a ball bearing. During experimental work in laboratory we distributed additive among the particles of powder coating through mechanical mixing. It forms a thin layer on surface of powder particles, which acts as a lubricant and allows the smooth sliding of the particles to each other. With the experiments we have tried to determine the optimal concentration of different fluidizing additives in the powder coating. Even a small addition can significantly increases fluidization and improve the flow of powder. By further raising the concentration of additive, fluidization increases to a certain extent, when it reaches its maximum. Rising the concentration even further result in degradation of flow properties due to overdosing of flow additive, which itself doesn’t flow well. For evaluating rheological property of the powder we use powder rheometer FT4, which operates on the principle of determining the torque and force required to rotate the rotary blade, submerged in to the powder. Measurements are repeatable and largely automated. We also measured angle of repose of prepared powder samples, observe powder behavior during application and properties of finished coating film. We had possibility to observe samples of powder under electronic microscope, which gave us overview of different structures of specific materials. Particle size distribution of powder has great importance as well. Higher proportion of fine particles decreases fluidization because of too high specific surface. Coarse particles, on the other hand, need more energy for their movement, which adversely affect powder flow. There is also a difference between the different fluidizing additives, derived from their different particle size, chemical composition, and surface treatment. praškasti lak praškasti premaz SiO2 pirogena silika Al2O3 fluidizacija reometer FT4 powder coating SiO2 fumed silica Al2O3 fumed alumina fluidization rheometer FT4 true true false [T. Rozoničnik] Slovenski jezik Angleški jezik Diplomsko delo/naloga 2016-08-24 11:07:53 2016-09-16 13:28:42 2022-06-28 03:08:31 2019-07-11 12:48:01 2016 0 Maribor 0 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 620.198:66.096.5(043.2) 20375830 URN:SI:UM:DK:JRXS2341 VS_Rozonicnik_Tomaz_2016.pdf VS_Rozonicnik_Tomaz_2016.pdf 1 1FA45D16D53990F9806944750FC03D3A 30b0e9ed4bdafa17e14cd01f05d24e5e70649845c257ee6d5cf763fa2d1ffd27 78d055c8-7c0d-11eb-bb7a-00155d0001ca https://dk.um.si/Dokument.php?lang=slv&id=104542 Fakulteta za kemijo in kemijsko tehnologijo 0 0 0