Vpliv sušilcev na kakovost premaznega filma v alkidnih premazih z visoko vsebnostjo suhe snovi : doktorska disertacija

slovenian

doktorska dela

2015

Univerza v Mariboru, Fakulteta za kemijo in kemijsko tehnologijo

Due to specific chemical structure of new high solid (HS) alkyd resins and consequently changed applicative properties the optimal combination and concentration of driers has been an important subject of research. Considering the declaired limited use of cobalt (Co) driers in decorative coatings we performed a comparative study of surface Co drier (Co ethylhexanoate) and alternative iron drier (Fe bispidon) in combination with through driers: strontium- (Sr carboxylate), zirconium- (Zr ethylhexanoic acid) and aluminum-based (Al organic complex) driers on curing process of HS alkyd coating. Mechanism and the kinetics of autoxidation were analysed by FT-IR spectroscopy. Further, drying time and physical properties such as rheological behaviour, film hardness, haze/gloss and color change were investigated. The quality of cured HS alkyd coating films after exposure in the humidity chamber was evaluated by electrochemical impedance spectroscopy (EIS). The autoxidation mechanism of HS alkyd coatings is similar for Co and Fe driers. However, they influence on kinetic parameters of autooxidation process differently. It was confirmed that Co drier also has higher catalytic activity effect on the surface of HS alkyd coatings. On the other hand, Fe drier catalyzes autooxidation process slowly but more homogeneously along the depth of a coating film. Antiskinning agent methyl ethyl ketoxime (MEKO) influences on the kinetics of autooxidation only in combination with Fe drier. Further investigation has shown that the addition of through driers has significant influence on activation and speed of autooxidation process. The addition of higher concentrations of through driers resulted in shorter final drying times and higher film hardnesses of cured HS alkyd coatings. Other physical properties were comparable in case of different combination of used driers. EIS analysis confirmed different influences of Co and Fe driers on the quality of cured coating films. The addition of lower concentrations of through driers in most cases resulted in the lowest values of Warburg diffusion and lower pore resistance through the coating film. Different behavior of Fe drier compared to Co drier requires a different optimisation approach of surface/through driers in HS alkyd coatings to achieve the defined applicative curing parameters. Nevertheless, Fe drier can be used as an alternative to Co drier for curing of HS alkyd coatings in decorative application.

07.08.2023