Novel solvent-free UV-photocurable varnish coatings based on acrylic telomers – Synthesis and properties

A new type of UV-photocurable liquid varnish binder was prepared by a solution-free UV-initiated telomerization process of butyl acrylate, acrylic acid, and styrene using tetrabromomethane (TBM) as a telogen and acylphosphine oxide (APO) as a radical photoinitiator. A multifunctional monomer (pentaerythritol triacrylate; PETIA) and a radical UV-photoinitiator (α-hydroxyalkylphenone) were tested as components of the final varnish compositions. An influence of TBM, APO and PETIA on optical and mechanical features of coatings was investigated. Relatively the highest hardness, adhesion to a glass substrate, and gloss values were revealed for a varnish based on a telomers syrup containing 5 wt. parts of TBM and 0.5 wt. part of APO (per 100 wt. parts of the monomer mixture). Moreover, the PETIA addition improved hardness, adhesion, scratch resistance as well as water and solvent resistance of the coatings.