| Abstract [eng] |
There are many environmentally friendly adhesive producers who produce various standards of adhesives for various applications. And they recommend using their products. It is not sure that these adhesives satisfy their needs. In this research suitable eco-friendly adhesive for hot stamping purpose from the producers was selected to improve their efficiency. The rheological behaviour of solvent based, and water based dispersions at constant rotational speed of D = 40, 60, 80, 100, 120 and 140 rpm for 1 hour have been investigated. It was determined that due to the four times higher concentration of film forming material in water based dispersions significantly higher dynamic viscosity values compare to those of solvent based was found. Dynamic viscosity is dependent on rotational speed. Effect of rotational speed on water based adhesive viscosity changes has uneven character. At lower than 100 rpm rotational speed (60 and 80 rpm) during first τ =10 min of testing viscosity tend to decrease, while at rotational speed of 120 rpm and 140 rpm slight increase of viscosity was found. At rotational speed of D=40 and 100 rpm dispersions showed behaviour characteristic for Newtonian fluids. The contact wetting angle relaxation of solvent and water based adhesives on the surface of aluminium coated and transparent hot stamping foil and tamper evident hot stamping foil have been investigated. Contact angle relaxation up to reaching constant (Young contact angle) value depends on the both adhesive and substrate nature. It was found that on both investigated hot stamping foil surfaces more intensive wetting angle shape changes were found during 2 first seconds, while for tamper evident film contact angle value gradually decreased. Young contact angle for solvent based adhesive was two time lower compare to the water based. Effect of surface nature on the Young contact angle value was found only insignificant. In order to increase wettability of water based adhesive to selected substrates different amounts (0.27 vol. % , 0.51 vol. %, 0.81 vol. % and 1.35 vol. % to total amount of dispersion) of ethyl alcohol and commercial non anionic surfactant was added. It was determined that independently on substrate nature addition of ethyl alcohol and non-anionic surfactants decreases the initial contact angle, but increases Young contact angle compare to those of pure dispersion. It was found that addition of surfactants results on the increase of the surface tension of dispersions. Higher effect using non anionic surfactant was found. Increase of amount of selected surfactants results on the decrease of surface tension relaxation duration. |
