Creep of high density polyethylene filled with multiwall carbon nanotubes

Abstract

The creep-recovery behaviour of two types of high density polyethylene (HDPE) filled with multiwall carbon nanotubes (MWCNT) is investigated. Nanocomposites with various contents of MWCNT were produced by using a commercially available masterbatch aimed to transfer the gained knowledge to an assessment of properties of industrial-scale products. Nanocomposites are characterized by the improved creep resistance compared to the neat polymers. Incorporation of 10 wt.% of MWCNT into the polymers resulted in a decrease of creep and residual strains for more than 3 and 5 times, respectively. The reinforcing effect of the nanofiller appeared also in a great increase of the elastic modulus (up to 100%) and ultimate strength (up to 60%) as well as a decrease of the coefficient of linear thermal expansion (down to 17%) of HDPE. Carbon nanotubes, being also good heat conductors, greatly contributed to the improvement of polyethylene’s thermal conductivity (up to 60%). Electrical percolation is determined below 2 wt.% of MWCNT. The electrical resistance changes monitored during creep-recovery tests are well correlated with the overall strain changes and residual strains in nanocomposites, that approve their in situ strain sensing capability during inelastic and long-term deformation.