Vpliv reoloških lastnosti tekočega premaza na lastnosti suhega filma na substratu

Kovačič, Anže (author), Slemenik Perše, Lidija (mentor)

Premazi so večfazni, kompleksni sistemi, ki se jih v enem ali več slojih nanaša na različne substrate. Njihov prvotni namen je zaščita substrata ter dodatek estetskega učinka, lahko pa imajo tudi sekundarne naloge kot so odboj vode, UV zaščita ter drugi. Večanje števila različnih substratov, huda konkurenca ter želje po enostavni uporabi ženejo podjetja premazne industrije v konstanten razvoj premazov. V grobem bi lahko sestavo premaza razdelili na 4 glavne komponente: veziva, topila, pigmente in aditive. Vsaka od teh skupin je skrbno sestavljena iz različnih komponent, ki kar maksimalno izpopolnjujejo premaz. Za premaz je pomembno, da je njegova aplikacija kar se da enostavna in da se kar najbolje prime podlage in s tem omogoči maksimalno zaščito substrata. V diplomski nalogi smo raziskovali, če lahko s pomočjo izmerjenih reoloških lastnosti tekočih premazov, določimo lastnosti filma na substratu. Za primerjavo smo določili reološke lastnosti dveh komercialnih premazov različnih barv (zelena in bela) ter ju med seboj primerjali. Eksperimentalno smo določili viskoznost in strižno napetost pri različnih strižnih hitrostih, mejno napetost, območje linearnega viskoelastičnega odziva, nato pa smo določili tudi frekvenčno odvisnost dinamičnih modulov v območju linearnega viskoelastičnega odziva. Rezultati so pokazali, da je pri vseh testih višje vrednosti konsistence izkazoval premaz bele barve, kar pomeni, da se bel premaz bolj upira delovanju zunanjih sil in zato težje prodira v mikroskopske pore na površini substrata. S tem se tudi težje veže na podlago, kar slabša njegove adhezijske lastnosti. Prav to domnevo smo potrdili tudi z izvedbo testa adhezije, ki je pokazal očitno slabše oprijemanje belega premaza na podlago. Na podlagi vseh opravljenih eksperimentov bi tako lahko zaključili, da z določanjem reoloških lastnosti tekočih premazov, lahko precej dobro določimo obnašanje premaznega filma po nanosu. Kljub temu pa je najzanesljivejši test filma premaza vseeno direkten nanos premaza na substrat ter opazovanje njegovega obnašanja skozi čas pod vplivom različnih dejavnikov.

• Language: Slovenian
• Keywords: premazi, reologija, adhezija
• Work type: Bachelor thesis/paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2020
• PID: 20.500.12556/RUL-119695
• COBISS.SI-ID: 30849539
• Publication date in RUL: 10.09.2020

Secondary language

• Language: English
• Title: The effect of rheological properties of liquid paint on the properties of dry coating on a substrate

Abstract

Coatings are multiphase, complex systems, that are applied on a substrate in one or more layers. They mainly serve to protect the substrate and improve aesthetic looks, but they can also have secondary functions like UV protection and water resistance. Coatings are subjected to constant research and development, because the number of different substrates is rising, the competition is strong and people are demanding simple ways of application. All coatings are generally made of 4 components: binder, volatile components, pigments and additives. Each of these components consists of carefully chosen materials, which improve the coating. It is very important that the coating is applied as easily as possible and that it adheres as strongly as possible to the substrate in addition to offering a maximum protection of the substrate. In my bachelor thesis the research was focused to whether it is possible to predict the behaviour of the dry film on a substrate from the determination of rheological data of the liquid paint. The rheological data of two paints of different colour (white and green) were determined and compared. The results of the rheological tests were the viscosity and shear stress at different shear rates, yield stress, the range of linear viscoelastic response and the dynamic properties in the range of linear viscoelastic response. The results of the rheological experiments showed that the white paint exhibited higher viscosity, shear stress and all others measured parameters. That shows that this coating is more resistant to the applied force, and does not allow easy penetration of the paint into the microscopic pores on the surface of a substrate. As a result, it is harder for the coating to bind in the surface of a substrate and thus the adhesion is weaker. The cross-cut tests gave similar results and showed a weaker adherence of the white coating to the substrate. The results of all tests showed that we can adequately determine the behaviour of a dry film by considering only the rheological properties of the liquid coating. However, the most accurate test of the properties of the dry film remains the application of the liquid coating to the substrate and long-time observation of the dry coating at various conditions.

• Keywords: coating, rheology, adhesion