A study on the role of silica nanoparticles on the viscoelastic behavior of polyethylene

In the current research the role of silica nanoparticles on the viscoelastic behavior of polyethylene (PE) has been investigated. To do so PE reinforced with different content of silica nanoparticles (i.e. 0, 1, 3 ,5 and 10 Wt%) have been produced using extrusion and injection molding methods. In order to investigate the viscoelastic properties, Dynamic mechanical thermal analysis (DMTA) has been performed. The results showed that at constant frequency (1 HZ) the storage modulus of all materials including PE and its nanocomposites decreased as temperature increased from -150 up to 120 oC. For example the storage modulus of neat PE and PE reinforced with 5Wt% SiO2 decreased from 2900 and 3400 MPa to 80 and 250 MPa respectively. Also the value of loss modulus increased as the polyethylene and it nanocomposites approached from low temperatures to the glass transition temperature. The loss modulus of PE and its nanocomposite has not any significant difference at low frequency. But this difference becomes more as frequency increases gradually. For example the difference between loss modulus of pure PE and PE/1Wt% SiO2 at 50 HZ and 250 HZ are about 8 and 15 MPa respectively. The highest amount of tanδ is for the pure polyethylene sample, and with the addition of SiO2 nanoparticles, the decreasing trend of tanδ observed. The lower values of tanδ indicating a reduction in the damping effect in composite samples compared to pure polyethylene.