Caracterización estructural, térmica y mecánica de nanocompuestos termoplásticos de matriz amorfa (PS, SAN y PMMA)

Abstract.
Polystyrene-matrix nanocomposites with lamellar nanoparticles of Mg-Al Layered Double Hydroxide (LDH) were prepared by the melt-mixing technique and investigated their structure, properties and fracture behaviour. Two different styrene polymers were used: Polystyrene (PS) and Poly(styrene-co-acrylonitrile) (SAN). Very slight increases in Young’s modulus, tensile strength and elongation at break were observed in PS nanocomposites, whereas market increases in Young’s modulus and elongation at break resulted in SAN nanocomposite with respect to the neat polymer. In this nanocomposite the tensile strength was reduced. X-ray diffraction (WAXS) spectra recorded on the PS nanocomposite displayed the LDH basal diffraction plane (003), indicating a not delaminated structure. However, the WAXS spectra of SAN nanocomposite did not display the (003) diffraction peak. Linear-elastic Fracture Mechanics (LEFM) parameters were obtained by means of three-point-bend fracture test. The fracture toughness (Kic and Gic) of PS nanocomposite was found to be slightly decreased with respect to the unfilled polymer, whereas a remarkable fracture toughness reinforcement resulted in the SAN nanocomposite. The analysis performed by SEM on the fracture surface of SAN nanocomposite revealed a great extension of plastic flow around the LDH nanoparticles.