Characterization of Polymer Nanocomposite Interphase and Its Impact on Mechanical Properties

TLDR

The polymer nanocomposite systems consist of alumina (Al₂O₃) and magnetite (Fe₃O₄) nanoparticles embedded in poly(methyl methacrylate) (PMMA) and polystyrene (PS) matrices. The study investigates the interphase structure between nanoparticles and polymer matrix using two approaches and proposes a new method for assessing nanoparticle flocculation. They used thermal gravimetric analysis and transmission electron microscopy to predict interphase structure and density in four nanocomposites, and Fourier transform infrared spectroscopy to analyze polymer–nanoparticle bonding and calculate interphase density in two PMMA systems, then correlated these structural predictions with mechanical testing and compared the findings to prior work. Al₂O₃ nanoparticles react more with the polymer matrix than Fe₃O₄, yet both exhibit weak interactions that produce low‑density interphases and more compliant composites, a conclusion supported by tensile, DMA, and nanoindentation tests that show the nanocomposites differ mechanically from their pure polymer counterparts.

Abstract

The structure of the interphase, a region between nanoparticle fillers and the bulk polymer matrix in a particle reinforced composite, was investigated using two different approaches. The polymer nanocomposite systems consists of alumina (Al2O3) and magnetite (Fe3O4) nanoparticles embedded in poly(methyl methacrylate) (PMMA) and polystyrene (PS) matrices. The first approach utilized data from thermal gravimetric analysis (TGA) and transmission electron microscopy (TEM) to predict the structure and density of the interphase for four nanocomposite systems. In the second approach, the nature of bonding between the polymer and the nanoparticle surfaces was analyzed using Fourier transform infrared spectroscopy (FTIR) to calculate the density of the interphase for two PMMA-based nanocomposite systems. Mechanical properties of these composites were correlated with the structure of the interface, and results from the two approaches were compared with previous studies. Moreover, by comparing results from the two characterization approaches, a new method for characterizing the degree of nanoparticle flocculation in a composite is also provided. The results indicate that Al2O3 nanoparticles are more reactive with the polymer matrix than Fe3O4 nanoparticles, but neither have strong interactions with the matrix, a fact that leads to low-density interphase and consequently results in more compliant composites. Tensile testing, dynamic mechanical analysis (DMA), and nanoindentation tests confirmed that these nanocomposite systems do not have the same mechanical properties as their respective pure polymer systems.