High performance unsaturated polyester based nanocomposites: Effect of vinyl modified nanosilica on mechanical properties

Influences of the vinyl modified nanosilica Aerosil (R) 380, i.e., vinyl and methacryloyl silane coupling agent and linseed oil fatty acids (BD) reactive residues, on the mechanical properties of the unsaturated polyester resins (UPes) based nanocomposites, was studied. The polycondensation of maleic anhydride and products of poly(ethylene terephthalate) (PET) depolymerization with propylene glycol, with and without separation of ethylene glycol, yields UPe1 and UPe2 resin, respectively. The hydroxyl terminated PET depolymerization products (glycolyzates) and UPes were characterized by acid and hydroxyl values, Fourier Transform Infrared (FTIR) and nuclear magneti resonance (NMR) spectroscopies. Transmission electron microscopy (TEM) confirmed that silica nanoparticles formed domains of aggregates in the polymer matrix. An increase from 195 to 247% of stress at break (sigma(b)), and from 109 to 131% of impact strength (sigma(i)) of UPes based nanocomposites was obtained for 1 wt% addition of vinyl modified silica. Flexural strength (sigma(f)) increase from 106 to 156% for both UPes based nanocomposites with 1 wt% addition of BD modified silica. Cross-linking density (nu), storage modulus (G'), tan delta and T-g of the nanocomposite were determined from the dynamic mechanical testing and discussed in relation to the structure of silica modification.