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Isotactic polypropylene–polyethylene copolymer microcellular foams of various relative densities were prepared using nitrogen (N2) in supercritical solid state. Also, series of copolymers with different polyethylene weight percentages were prepared. Mechanical properties (compression and impact conditions) dependence on relative density, PE content, and strain rate was studied. Results showed that yield stress gradually decreased with lower density. The yield stress of PP copolymer foams decreased with the relative densities, and was always smaller than that of the solid PP copolymer. Nevertheless, the sensitivity to strain rate effect decreases at impact velocities. Analytical models were developed including the effects of both relative density and strain rate. [ABSTRACT FROM AUTHOR]

• TCD was applied at high loading rates to failure of notched additive manufactured PA12. • A probabilistic fracture toughness at different loading rates has been determined. • Fracture toughness at different orientations was measured in additive manufactured PA12. • An assessment of the Hopkinson bar experiments with notched samples is performed. In this work, the applicability of the Theory of Critical Distances to the study of failure at high-loadings rates of polyamide 12 notched specimens additively manufactured by selective laser sintering, is evaluated. An experimental and numerical study has been carried out and values of modulus of elasticity, tensile strength and fracture toughness have been obtained. under static and dynamic conditions. The effect of orientation has also been analyzed, testing samples parallel and perpendicular to the layers of material deposited. [ABSTRACT FROM AUTHOR]

Abstract: Tensile tests were conducted on several ethylene–propylene block copolymers with different ethylene content, over a range of temperatures (−120 to 23°C) and strain rates, 10−4–10−2 s−1. The effect of temperature and strain rate on elastic modulus, Poisson’s ratio and yield stress has been analyzed. To determine the elastic properties, a video-extensometer was used to determine the deformation field. The experimental results about yielding are interpreted in terms of the well known principle of temperature–time equivalence. Several models have been considered to explain the significant increase in the yield stress at low temperatures or high strain rates. [Copyright &y& Elsevier]

Abstract: Yielding behaviour under compressive loading of two materials based on polypropylene, an isotactic homopolymer and an ethylene–propylene block copolymer, is studied at different strain rates and temperatures. Quasi-static tests, performed in electromechanical machines, and dynamic tests, carried out in a Hopkinson bar, were compared and simultaneously analyzed to generate a master curve representative of the material yielding, assuming the strain rate-temperature superposition principle. Experimental data were fitted to equations based on the cooperative model for semi-crystalline polymers. [Copyright &y& Elsevier]