SYNTHESIS AND CHARACTERIZATION OF UV CURABLE ACRYLATED URETHANE PREPOLYMERS .2. EFFECTS OF VARIOUS DIACRYLATES AS DILUENTS AND RELATIVE-HUMIDITY ON MECHANICAL-PROPERTIES OF TDI PEG/HEMA-BASED POLYMERIC FILMS/

Various UV-curable acrylated urethane prepolymers based on tolylene-2, 4-diisocyanate (TDI), poly(ethylene glycol) (PEG 400), and 2-hydroxyet hyl methacrylate (HEMA) were synthesized. The effects of reactive dilu ent types, the composition of the products and of different humidity c onditions on mechanical properties of cured films were investigated. E ffects of diethylene glycol diacrylate (DEGDA) and thiodiethylene glyc ol diacrylate (TDGDA) as reactive diluents on tensile strength, elonga tion and Young's modulus values of the UV cured films were examined sy stematically. The results show that the increase of relative humidity from 50 to 95% leads to a decrease in tensile strength and Young's mod ulus values of polymeric films. The decrease of these mechanical prope rties in high relative humidity is due to the formation of hydrogen bo nding in the polymer chain caused by water molecules.