Effects of interlayer density and surfactant on coupled thermal stress and moisture absorption in modified montmorillonite/polypropylene nanocomposite

Abstract

Modified montmorillonite/polypropylene nanocomposites (NCs) are increasingly used in industrial applications such as subsea pipelines because hexadecyltrimethyl ammonium montmorillonite (HDTMA+‐Mt) enhances thermomechanical and barrier properties of the amorphous polymer. Two coupled physics of moisture adsorption and thermal loading are investigated. Molecular dynamics simulates HDTMA+‐Mt polymer NC using three force fields including polymer consistent force field and condensed‐phase optimized molecular potentials, and embedded‐atom method. Mechanical properties and self‐diffusion coefficient are investigated at temperature levels of 100 and 298 K, and water content of 0.021 and 0.133 g/g. These properties are evaluated at 1.0 atm pressure for four different volume fractions (vol%) of the HDTMA+‐Mt. The modeling procedure is verified by obtaining the glass transition temperature (Tg) of the NC by scanning the temperature from 200 K (glassy state) up to 325 K (rubbery state). It is observed that the Tg is very close to the experimental value available in the literature. The result of the modeling shows that the increase of clay content of the NC decreases the self‐diffusion coefficient of the material. It is seen that the clay nanoparticle can significantly hinder the degradation of mechanical properties of the NC even when both temperature and water content increase.