Variations of tunneling properties in poly (lactic acid) (PLA)/poly (ethylene oxide) (PEO)/carbon nanotubes (CNT) nanocomposites during hydrolytic degradation

The combination of poly (lactic acid) (PLA) with water-soluble poly (ethylene oxide) (PEO) and carbon nanotubes (CNT) presents interesting results during hydrolytic degradation. This paper investigates the conductivity of PLA/PEO/CNT nanocomposites during degradation in phosphate-buffered saline (PBS) solution. A simple model is suggested to express the conductivity of samples during degradation by CNT properties, degradation fraction, interphase thickness and tunneling properties. The calculations of developed model are compared to the experimental data and the variations of tunneling resistivity and tunneling distance are explained. Moreover, the parametric examinations are applied to confirm the developed model. The predictions of conductivity acceptably agree with the experimental data during degradation. The degradation reduces the tunneling resistivity and tunneling distance between neighboring CNT, due to the exclusion of polymer matrix. The results demonstrate the positive effects of high degradation fraction, thick interphase, large tunneling diameter, slight tunneling resistivity and short tunneling distance between adjacent CNT on the conductivity of degraded nanocomposites. The current study can provide useful guidelines for analysis of conductivity in nanocomposites during degradation. (C) 2018 Published by Elsevier B.V.