Molecular dynamics in polyester resin doped with barium titanate nanoparticles studied by 1H NMR techniques

BaTiO3/polymer composites, which combine the high dielectric constant of ceramics with the high dielectric strength of polymers, are used in modern microelectronics as capacitors, piezoelectric transducers and optoelectronic elements. The aim of the work was to determine the effect of barium titanate (BT) nanoparticles on physical properties of polyester resin (PR). The introduction of nanoparticles into a cross-linked polyester resin induces changes in its molecular structure and dynamics as a result of the particle-polymer interface. Molecular dynamics of polyester resin filled with barium titanate nanoparticles with BT content of 0.1% wt. and 1% wt. was studied. The internal motion of cured polyester resin and new PR/BT composites was investigated by different H-1 NMR techniques. The temperature dependences of the spin-lattice relaxation times T-1 in the laboratory frame and the frequency dispersions of the spin-lattice off-resonance relaxation times T-1 rho(off) in the rotating frame were determined. Also, the first derivative of the absorption H-1 NMR signal was recorded and the second moment of the signal was determined as a function of temperature. Differential Scanning Calorimetry was employed to study the thermal properties of the samples. The results showed that BT nanoparticles influenced the molecular dynamics and thermal properties of polyester resin. The addition of BT nanoparticles leads to a decrease in the correlation times and in the activation energy of internal motion in composites, compared with those for pure polyester resin. What is more, the glass transition temperature T-g and the thermal decomposition temperature T-D of polymer composites shift to lower values.