Temperature-affected mechanical properties of polymer nanocomposites from glassy-state to glass transition temperature

Abstract

In this study, the effects of nanoparticle content, polymer/particle interphase, aggregation/agglomeration, and temperature variation on the thermo-mechanical properties of polymer nanocomposites, containing spherical nanoparticles, were investigated. The temperature distribution in the samples was evaluated using a new proposed model on the thermal conductivity of nanocomposites (error < 4%) which also represented unique information about the thermal and physical characteristics of the interphase region. Consequently, the temperature dependency of all physical/mechanical parameters (tensile modulus, yield strength, density, specific heat capacity, etc.) was defined and the results were used to simulate the response mechanism of under-stress nanocomposite samples at a specific thermal condition. PS and PMMA nanocomposites samples containing 1, 2, 3 and 4 vol % of the surface-modified silica nanoparticles were prepared via melt mixing and subjected to tensile, rheology, heat conduction and DMA tests whose results were used to evaluate the accuracy and analyzing the theoretical obtained data. It was revealed that the increment of the nanoparticle content increases the thermal conduction coefficients of the polymer/particle interphase region and the entire system while it decreases the interphase thickness. This led to more significant negative effects of the temperature on the mechanical properties of the nanocomposites. Also, at temperatures about Tg, the under-stress samples with the nanoparticle content of 4 vol% experienced the plastic deformation sooner than the samples with nanoparticle content of 1 vol%.