The mechanical behavior of springy polypropylene

Abstract

To obtain further details of the unusual behavior of the “hard elastic,” “springy” form of polypropylene (SPP), various loading conditions were studied with an Instron model 1130. Specifically, the variation of the elongation at rupture with change in gauge length and strain rate has been determined. The nature and degree of the specimen hysteresis resulting from various loading cycles have been characterized. The ability of this material to recover from large extensions customarily expected to be permanent deformation has been identified and the time dependency of this recovery has been determined for strain levels of 10, 25, 50, and 100 percent of the original sample length. The effects of submitting the material to conditioning treatments, e.g., immersing in saline solutions of various electrolyte concentrations and autoclaving for 30 min at 250°F and 15 psig have been studied. Characterization of the stress relaxation behavior of the polymer has been made. Fatigue behavior has been identified utilizing a novel testing apparatus which permits load‐cycling of the fiber. Rheovibron work has facilitated calculation of the activation energy of the second order relaxation of SPP from tan δ vs temperature data. Stoll abrasion testing results on SPP tubular knit fabric and multifilament yarn have been compared to normal polypropylene and Dacron®.

Hard‐Elastic fibers. (A review of a novel state for crystalline polymers)

“…Similar results accrue upon autoclaving the material. Cannon et al (1975) indicate that most water conditioning treatments of the springy form of polypropylene do not affect the properties of SPP and extensive results are available in their reports.…”

“…Maximum stress supported by springy polypropylene as a function of strain rate(Cannon et al, 1975). Typical stress-strain curves for two cycle loading of springy polypropylene to 50% elongation at a strain rate of 2 in./min(Cannon et a]., 1975).…”

“…Tension-tension fatigue behavior of springy polypropylene at room temperature and 50 Hz(Cannon et al, 1975).…”

A Study on the Relationship Between the Crystal Structure and Hard Elasticity of PVDF Fibers

“…The generalized properties of these row structure materials include high elastic recovery from very high strains such as 50–95% recovery from 100% extension, a reversible reduction of density with an enormous increase of pore volume upon stretching, and high deformability with good recovery at liquid nitrogen temperature. Polymers that can be used for the formation of such elastic materials include semicrystalline polymers as polyoxymethylene (POM),1 poly(propylene) (PP),2 poly(4‐methyl‐1‐pentene) (PMP) (TPX),3 polyethylene (PE),4 etc. The mechanism of elasticity is based on splaying apart of their lamellae, and their reversible bending and torsional deformation during macroscopic deformation of the materials 5.…”

Effect of stretching on structure and properties of polyethylene hollow fiber membranes made by melt‐spinning and stretching process

“…One possible explanation for the above phenomena may be that when the hollow fibers were stretched, the parallel lamellae in the fiber wall passed through different transition states, such as slipped, deformed, and separated, leading to the formation of a microfibril structure. 11,12 During the stretching processes, the piled lamellar structure was separated; therefore a number of micropores formed while the lamellar spacing enlarged. This change was confirmed by observing the morphology of stretched and unstretched hollow fibers through FESEM (Fig.…”