Pre-yield tensile set of a semi-crystalline polymer, its blend and composite

Abstract

Tensile set was studied at low strains on polypropylene, aliphatic polyketone, rubber toughened blends and CaCO 3 particle toughened composites. The rubber in the rubber toughened blends had a particle size of 0.7 lm. The CaCO 3 particles had a size of 0.7 lm and had been coated with stearic acid.Step-cyclic loading was applied in 1% strain incrementals at a strain rate of 10 -2 s -1 . The maximum strain applied was 20%. The temperature of the test bar was studied with an infra-red camera. Pre-yield deformation is normally assumed to take place in a nonlinear elastic manner. However, for polypropylene and polyketone elastoplastic deformation starts at low strains. For PP the onset of tensile set is at very low strains and increases with strain. The tensile set at the yield point was only 50% and at the drawing strain 100%. Polyketone had a similar tensile set development but shifted to slightly higher strains. Here too the tensile set at the yield point was about 50% and at the drawing strain 100%. The temperature of the non yielded material was found to rise in polyketone a 7°C.The rubber toughened blends had at low strains a higher tensile set, but after the yield strain the set was similar to the base polymer. At 5% strain the tensile set increased with rubber content. The sub micron CaCO 3 particle toughened composites increased the tensile set too. The tensile set is a simple technique for studying the pre-yield behaviour of multi phase systems.

Anomalous Mechanical Response of Stretched Film of Poly(3-Hydroxybutyrate-co-3-Hydroxyhexanoate)

“…The stress-strain curve eventually became an inverted "S" shape, which was resembling to the stress-strain curve expressed by the non-Gaussian statistical model of rubber elasticity [46,47]. This result differed markedly from those reported previously for various plastics [29,[31][32][33][34][35][36][37][39][40][41]. The present result suggested that rubber-like deformation occurred during the reloading process.…”

“…Therefore, various approaches have been developed to clarify the plastic deformation behavior of polymers. One of the phenomenological methods to characterize plastic deformation is loading, unloading, and reloading cyclic tests [29][30][31][32][33][34][35][36][37][38][39][40][41], which are also used to investigate the Bauschinger effect [30]. In glassy plastics, the residual strain after an unloading process, i.e., plastic strain, is proportional to the applied strain beyond the yield point [29,34,37].…”

Highly Solvent‐Resistant Polystyrene Based on Uniform Tetraamide Units

“…For calculating crystallinity in copolymer, the peak height of 1630 ( h (1630 cm −1 ) ) and the peak height at 1660–1670 ( h (1670 cm −1 ) ) are taken to represent crystalline and their amorphous segments, respectively. Similar calculations are performed on several amides containing TPEs …”