Study of the fracture behavior of natural rubber and polybutadiene based compounds : structure to properties correlation (original) (raw)

The purpose of this thesis work was to study the effect of sulfur (S) content, carbon black (CB) type and carbon black content on the ultimate properties of three different rubber compounds, based on natural rubber, polybutadiene and their 50/50 blend. First, swelling test, dynamic mechanical analysis and tensile test were carried out to obtain information on physical characteristics of the compounds: crosslink density, filler-filler and filler-rubber interactions and the maximum chain extensibility. Then, ultimate stress and strain from uniaxial tensile tests and the fracture toughness, using notched pure shear specimens and adopting J-integral fracture mechanics approach, were evaluated. Finally, a correlation between the ultimate mechanical properties and the physical characteristics of the compounds was attempted. The main results obtained are:  high fracture toughness is achieved when “sideways” cracks, perpendicular to the notch plane, develop before the onset and propagation...