Recovery of post-yielding deformations in semicrystalline poly(ethylene-terephthalate)

Strain recovery of post-yield compressed semicrystalline poly(butylene terephthalate)

“…Contrary to glassy polymers, the strain recovery process extends up to temperatures well above T g of the amorphous phase [20]. This phenomenon could be tentatively ascribed to the presence of a mobility gradient due to the interphase between the crystalline domains and the amorphous regions [19,20,34,56,57]. Fig.…”

“…Some peculiar aspects of semicrystalline polymers are the extension of the strain recovery processes at temperatures much higher than T g [19,20,22,23,26,31,34], and the appearance of a certain irreversible deformation, even when heated at temperatures much higher than T g and within a few degrees of the melting point [20,22,23,34]. This research group recently studied the strain recovery behaviour of highly deformed semicrystalline polymers such as nylon-6 (PA6), poly(ethylene terephthalate) (PET), and poly(ethylene 2,6-naphthalenedicarboxylate) (PEN) tested in tension [19,34], and of poly(butylene terephthalate) (PBT) tested in compression [20]. Similar to amorphous polymers [27,29], the strain recovery data have been treated according to a timeetemperature superposition approach, thus obtaining strain recovery master curves.…”

Post-yield compressed semicrystalline poly(butylene terephthalate): energy storage and release

“…This phenomenon has been widely observed and studied on highly deformed glassy polymers [1,9 -23], where the exothermal peak, interpreted as an evidence of the relaxation process connected to the deformation recovery, usually extends from the deformation temperature up to glass transition. The wider extent of the energy release process for semicrystalline polymers, already reported for PET [25] and PBT [27], has been attributed to the mobility gradient due to the interphase between the crystalline domains and the amorphous regions [25 -27,49]: as a consequence, the relaxation process for semicrystalline polymers spreads up to temperatures well above T g even if it can be still attributed to a release of internal energy stored in amorphous regions [1].…”

“…The amount of energy internally stored for a given deformation level seems to be affected by the loading conditions, such as strain rate [1,14] and deformation temperature [1,12,15,25,27], but the available literature data are quite scarce. Since most of mechanical properties of polymers are strongly dependent on time and temperature, it is therefore of general interest to study how parameters like strain rate and deformation temperature may affect their energy storage ability.…”

The Nonlinear Time‐Dependent Response of Semicrystalline Polymers: Correlations Between the Configurational Entropy and the Rate of Rearrangement of Chains

“…Neglecting the energy of interaction between active strands, [38] we arrive at the formula It follows from Equation (6), (9), (14) and (23) that…”