Influence of Ageing with UV Radiation on Physicochemical Properties of Acrylic-Polyurethane Coatings

Abstract

Investigated systems of acrylic-polyurethane coatings consisted of three kinds of coatings: base coat (acrylic), intermediate (polyurethane) and top coat (acrylic); each made up of two layers. Mean thickness of the coating system was equal (145 ± 1) µm. In time of accelerated UV ageing, electromagnetic radiation was emitted of wave length in the range (300-400) nm which was progressively inducing a destruction of coatings chemical structure, especially photooxidation and photolysis of coating material. Carried out X-ray investigations revealed increased contents of oxygen in aged coatings due to their photooxidation which resulted in increased tendency of coating microfragments to chip off from surface layer with the ageing time flow. The hardness increase of UV aged coatings was also observed which intensified their surface layer brittleness. This contributed to their thickness decrease by more than 10% after 2016 h of ageing. Photodestruction of UV aged coatings was documented as well by characteristics obtained during investigations carried out with DMA method use. A noticeable physical destruction of the coatings was observed in the form of silver cracks, etchings and grooves in surface layer as well as craters extending also into interlayer. Processes of physical and chemical destruction undergoing in aged coatings influenced roughness profile change and coatings surface topography shaping. After 2016 h of UV ageing, the roughness parameters (Ra, Rz, Rt) increased several times. Long-lasting UV radiation influence on the surface of investigated acrylic-polyurethane coating systems contributed to their decorativeness loss. Microscopic examinations revealed colour change (yellowing) of blue pigment contained in polyurethane interlayer. Decline in coating gloss was also observed as the result of surface roughness increase.

Effect of grey component replacement processing and varnishing on the light fastness of colours on cardboard prints

“…Specifically, removal of the ink from the substrate due to smudging meant the amount of scratching was decreased. Smears on the print caused by the smudging of the ink are apparent on the unaged UV‐coated print (Figure 10A), while the scratch marks are more evident on the aged UV‐coated print (Figure 10B), possibly as a result of the increased brittleness of the aged UV‐varnish 34 …”

“…Smears on the print caused by the smudging of the ink are apparent on the unaged UV-coated print (Figure 10A), while the scratch marks are more evident on the aged UVcoated print (Figure 10B), possibly as a result of the increased brittleness of the aged UV-varnish. 34 WD varnish did not visibly improve the resistance to abrasion of the unaged and aged prints (Figure 11) compared with the uncoated prints (Figure 9). Damage on the print surface in the form of smudged thin scratch marks is visible on both the aged and unaged samples.…”

Effect of Graphene Oxide on UV-Thermo-Humidity Degradation of Environmentally Friendly Alkyd Composite Coating

“…These characteristics can be explained by the fact that GO particles are much harder than polymer matrix, so the more GO content, the harder the relative hardness of the coating. However, if GO content increases continuously (to 1.5 wt.%), GO particles tend to agglomerate into larger particles to release surface energy and adhesion and flexural would decrease [24,25]. M3 expressed the best properties of environmentally friendly alkyd composite coating, so it was chosen for further study.…”

Effect of UV Light on the Barrier Performance of Aluminum Powder/Epoxy Coating

“…These factors degrade the performance of coatings and reduce their useful life [5,6]. In particular, under UV irradiation, epoxy resins exhibit yellowing, brittleness, cracking, and other performance degradation phenomena, which seriously affect their protective effect on metal substrates [7,8].…”