Determining the thickness and modulus of the nano-metric interphase region using macroscopic modulus data in exfoliated polymer-clay nanocomposites

TL;DR

This study develops a method to predict the nanometric interphase thickness and modulus in polymer-clay nanocomposites using macroscopic elastic data, validated by literature data and applicable to similar systems.

Contribution

It introduces an analytical approach combining finite element simulations and nanoscale equations to estimate interphase properties from macroscopic measurements.

Findings

Predicted interphase thicknesses align with experimental reports (2-8 nm).

The method is validated with literature data.

Applicable to a wide range of isotropic triple-phasic systems.

Abstract

This paper is an attempt to predict the thickness and modulus at the nanometric interphase region with the knowledge on the macroscopic Young's modulus in the polymer-clay nanocomposites. First, a systematic design of 20160 linear elastic finite element simulations are used to derive an analytical equation between the interphase thickness, the interphase modulus, the nanoclay content and the macroscopic Young's modulus of the nanocomposite. Four calibration parameters in this equation are calculated based on the reported data about NYLON6-MMT nanocomposite. Next, an analytical nanoscale equation is developed to satisfy the necessary boundary conditions at the nanometric interphase. Finally, the interphase thickness and modulus are calculated by the intersection between the two equations. The validity of predictions are examined using two distant data sets in literature. The predicted interphase thicknesses are consistent with the experimental reports which situate around 2-8 nm in this nanocomposite. The presented approach can be used in design and prediction of mechanical properties in wide range of isotropic triple-phasic systems with structural features similar to polymer clay nanocomposites.