The implementation of this technical action was to find out the experimental conditions for UV curing and the compositions of UV curable mixtures containing as much as possible renewable monomers and polymers to create light-curable coatings, adhesives or inks.
The curing can occur when the emitted UV and visible light is as much as possible absorbed from photoinitiator, which promotes the crosslinking reactions by free radical mechanism involving reacting monomers (DEI, DBI and UP). Typically, UV technology is commonly used with a starting liquid thin film of ink, adhesive or varnish is applied on a glass, plastic or metal surfaces. The liquid film is rapidly vitrified (cured) after UV light exposure in few seconds. The UV technology advantages are the very rapid cure and the absence of solvents to form a thin film (max 0.5 mm) on a substrate.
For this action were prepared several UV curable mixtures containing: i) 50-70% by of wt IA unsaturated polyesters, ii) 30-50% by wt of IA-reactive diluents such as DBI, DEI and DPI obtained in the technical activity B1; iii) 3,0-5,0% by wt of commercially available photoinitiators.
The UV curing efficiency were demonstrated by measuring after exposure the hardness of the cured film of 6 mils (0,15 mm) deposited on an aluminium film or glass slide. Some improvements were carried out by using both as reactive diluent some commercially available methacrylated derived from fossil resources.
The best performances of the UV curable mixtures containing IA-based unsaturated polyesters and monomers were also used for the ink preparation by adding pigments in powder of 5% by wt of titanium dioxide (Evonik) for white colour, 5% of carbon black (clariant) for black colour and 5% by wt of (red 8854, clariant) for red colour. Under the same UV irradiation conditions, the König hardness of the UV clear and pigmented mixtures, containing 70% by wt of IA-based monomers and unsaturated polymers derived from renewable resources, are compared with the reference mixture obtained by all conventional methacrylated monomers and polymers.