Photopolymerization of dendritic methacrylated polyesters. III. FRP composites

Abstract

In two previous articles, the preparation, modification with epoxy methacrylate and methacrylic anhydride, and properties of dendritic aromatic polyesters with structural symmetry, a high degree of branching, and a high density of terminal functionality were described. The resulting polyester resins were cured by addition of benzildimethylketal (Irgacure 651) as the photoinitiator and trimethylolpropane triacrylate (TMPTA) as the comonomer and irradiated with UV light as laminates with 35 wt % glass fiber mats. After short irradiation times (0.02-0.10 s) at room temperature, the laminates with excellent mechanical properties which are comparable with the thermally cured linear unsaturated polyester in styrene and UV-cured linear epoxy acrylate-modified unsaturated polyester composites were obtained. The addition of 10-40 wt % TMPTA had only small effects on the mechanical properties, except on tensile strength, which decreased about 15%. The dendritic polyesters have low viscosity and a much higher curing rate than those of corresponding linear unsaturated polyesters and are, therefore, of great interest for industrial applications.