The Effect of Processing on the Electrical Properties of Exfoliated Graphite Nanoplatelet/Polylactic Acid Nanocomposite Films

摘要

The potential for engineering/tailoring properties, specifically electrical properties, ofrnpolylactic acid (PLA) nanocomposite films is examined by comprehensively studyingrnprocess-structure-property relationships. This work focuses on investigating the effectrnof composite processing methods and conditions on the electrical response ofrnexfoliated graphite nanoplatelet (GNP) / PLA films. GNP are incorporated into thernPLA matrix either via polymer dissolution / solution casting or via melt compoundingrnand fiber melt spinning / compression molding to produce films of ~160 μm thickness.rnIn order to investigate the effect of polymer crystallinity on the electrical response ofrnthe films, the melt compounded / compression molded films are either cooled rapidlyrn(~16℃/min and denoted fast cooled or FC) or cooled slowly (~0.4℃/min and denotedrnslow cooled or SC) to alter the matrix crystallinity. Crystallinity and crystal structurernof the composite films are investigated using differential scanning calorimetry (DSC)rnand X-ray diffraction (XRD). Mechanical properties are examined in tensile modernusing a standard tension setup. Electrical properties of the films are examined usingrnimpedance spectroscopy (IS). The SC films percolated between 1 and 5wt% of GNP,rnfollowed by the solution cast films which percolated between 5 and 8wt% of GNP,rnand finally the FC films had the highest percolation between 12 and 15wt% of GNP.rnFurthermore, the percolation of the solution cast films can be lowered to below 5wt%rnof GNP by minimizing voids present in the films which can be done via compression.rnThe differences in percolation can be attributed to differences in compoundingrntechnique and the polymer matrix crystallinity.