Photocrosslinking Of Acrylated Prepolymer Case Study

2.5. Characterization Methods
1H–NMR and 13C–NMR spectra of HPPP, BOMP and HVPA were taken in CDCl3 on Bruker DPX–300 MHz spectrometer using tetramethylsilane (TMS) as an internal standard. FT–IR spectra of the synthesized compounds, HPPP, BOMP, HVPA and photocrosslinked polymers were recorded on Perkin-Elmer system 2000 (4000–400 cm–1) spectrometer, using KBr pellets. Medium pressure mercury vapour lamp to the power output of 125W/cm2 was used for the photocrosslinking study. The viscosity of the photocurable formulation was measured by Brookfield Viscometer RVDV–II+ (USA). The hardness of photocrosslinked polymer films was determined by A–Type JIS K6301 hardness tester (Germany).

2.6. Photocrosslinking of Acrylated Prepolymer
The photocurable formulation containing the prepolymer, HVPA (70%), diluent, TEGDA (30%) and the photoinitiator, DMPA (0.25%) were coated on a thin glass slide for 25 mm thickness, and then exposed to UV–radiation at a distance of 3 cm from
Photocrosslinking studies was performed by irradiating the photocrosslinkable mixture containing the HVPA with TEGDA in the presence various concentration of DMPA using medium pressure mercury vapour lamp. The probable mechanism of free radical photopolymerization of HVPA with TEGDA in the presence of DMPA under UV–radiation was suggested. It was found that PDC, gel content (%) and hardness of the photocrosslinked polymers increased with increasing irradiation time and DMPA concentration whereas Rp increased rapidly, then decreased and became a constant. To compare PDC of the synthesized polymer, HVPA and commercially available polymer, BISGA, the PDC of HVPA was higher than BISGA, which indicated that reactivity of HVPA higher than BISGA and which showed that synthesized prepolymer, HVPA suitable for indusial application such as coating, UV–curable inks