Mechanical properties of PMMA sepiolite nanocellular materials with a bimodal cellular structure

TL;DR

This study investigates how sepiolite nanoparticles influence the mechanical properties of bimodal cellular PMMA, revealing enhanced fracture toughness and mild changes in modulus and strength due to nanoparticle dispersion and migration during foaming.

Contribution

It introduces a novel bimodal cellular PMMA nanocomposite with sepiolite, demonstrating how nanoparticle dispersion affects mechanical properties in foamed structures.

Findings

Relative fracture toughness significantly increases with sepiolite addition.

Relative modulus remains stable across porosity range, with slight enhancement near 50% porosity.

Relative strength mildly decreases as sepiolite concentration increases.

Abstract

Bimodal cellular poly(methyl methacrylate) with micron and nano sized (300 to 500 nm) cells with up to 5 weight percent of sepiolite nanoparticles and porosity from 50 weight percent to 75 weight percent are produced by solid state foaming. Uniaxial compression tests are performed to measure the effect of sepiolite concentration on the elastic modulus and the yield strength of the solid and cellular nanocomposites. Single edge notch bend tests are conducted to relate the fracture toughness of the solid and cellular nanocomposites to sepiolite concentration. The relative modulus is independent of sepiolite content to within material scatter when considering the complete porosity range. In contrast, a mild enhancement of the relative modulus is observed by the addition of sepiolite particles for the foamed nanocomposites with a porosity close to 50 percent. The relative compressive strength of the cellular nanocomposites mildly decreases as a function of sepiolite concentration. A strong enhancement of the relative fracture toughness by the addition of sepiolites is observed. The enhancement of the relative fracture toughness and the relative modulus (at 50 percent porosity) can be attributed to an improved dispersion of the particles due to foaming and the migration of micron sized aggregates from the solid phase to the microcellular pores during foaming.