Rubber Particles from Tires Out of Use as Toughness Modifiers of Epoxy-Based Thermosets

Abstract

Rubber particles from tires out of use (TOU) were used to modify an epoxy-based thermoset. The effect of size and particle content were evaluated. Three bending point and Charpy tests were carried out to study the mechanical behavior of the materials. A steady decrease in the critical stress intensity factor, K_Ic, with the content of TOU was observed, being attributed to the fact that the particles might also act as defects in the polymer matrix. Fractographic analysis confirmed that filled specimens showed localized shear yielding at the end of the particles along the crack propagation direction. No signs of cavitation mechanism were found on the surfaces of fracture, evidencing an extraordinary interfacial adhesion. The total energy absorbed at break increased as the size of TOU particles decreased, pointing out that particle size is crucial for the performance of these materials. Matrix yielding and plastic deformation were considered to be the main toughness mechanisms.

KEYWORDS:

• Epoxy
• Fracture mechanics
• Interfaces
• Interphases
• Mechanical properties
• Rubbers

ACKNOWLEDGMENTS

This research has been completed with funding from the Ministerio de Ciencia e Innovación projects: MAT2007-61607, MAT2010-16815, and AIB2010PT-00267. Authors gratefully acknowledge the department of “Mecánica de Medios Continuos y Teoría de Estructuras (UC3M)” and particularly David Arias, for their technical support in Charpy tests.