Tensile Deformation of Oriented Poly(ε-caprolactone) and Its Miscible Blends with Poly(vinyl methyl ether)

Abstract

The structural evolution of micro-molded poly(ε-caprolactone) (PCL) and its miscible blends with noncrystallizable poly(vinyl methyl ether) (PVME) at the nanoscale was investigated as a function of deformation ratio and blend composition using in situ synchrotron small-angle X-ray scattering (SAXS) and scanning SAXS techniques. It was found that the deformation mechanism of the oriented samples shows a general scheme for the process of tensile deformation: crystal block slips within the lamellae occur at small deformations followed by a stress-induced fragmentation and recrystallization process along the drawing direction at a critical strain where the average thickness of the crystalline lamellae remains essentially constant during stretching. The value of the critical strain depends on the amount of the amorphous component incorporated in the blends, which could be traced back to the lower modulus of the entangled amorphous phase and, therefore, the reduced network stress acting on the crystallites upon addition of PVME. When stretching beyond the critical strain the slippage of the fibrils (stacks of newly formed lamellae) past each other takes place resulting in a relaxation of stretched interlamellar amorphous chains. Because of deformation-induced introduction of the amorphous PVME into the interfibrillar regions in the highly oriented blends, the interactions between fibrils becomes stronger upon further deformation and thus impeding sliding of the fibrils to some extent leading finally to less contraction of the interlamellar amorphous layers compared to the pure PCL.3

Insight into unique deformation behavior of oriented isotactic polypropylene with branched shish-kebabs

“…This principle ingeniously unified the very beginning 'slips within the lamellae including crystallographic fine slips and intralamellar mosaic block slips' stated by Peterlin et al [69e71] and 'stressinduced melting and recrystallization' insisted by Flory et al [72] during deformation of semi-crystalline polymers in early years. This principle has been proven to be true in isotropic polymers with spherulites and anisotropic samples with deformed spherulites [42,48,54,55,73]. There needs to be verified whether it is still applicable to the deformation of oriented polymers.…”

“…11 [11]. In general, a 4-point or even 6-point scattering feature can be expected to appear in the off-axis during the stretching of isotropic semi-crystalline polymers prior to finally concentrating in a 2-point scattering feature, which is thought to be caused by the oblique crystal orientation [68,73,75]. Even though it is reported that oblique crystal orientation usually gives rise to symmetric off-axis scattering [75], specifically, coarse slip of main lamellae.…”

“…3b), which seems a little different from the general situation. This preferentially tilted direction may be triggered by a slight deviation between the molding direction (normals to all lamellae) and tensile direction [73], so that normals to all lamellae are inclined in one preferential direction upon the deformation, as a result of fine slip of parent lamellae. Although the long period of kebabs does not apparently increase (Fig.…”

Hierarchical microstructure changes and the molecular mechanism of polypropylene under a critical failure strain during creep

“…Because the samples were not measured at one time, two conditions were applied. 1060 mm for sample-todetector distance and 60 min for exposure time were applied for samples with ε ¼ 0, 5,15,17,20,25,30, 110% as the final strains, while 1753 mm for sample-to-detector distance and 20 min for explosion time were applied for samples with ε ¼ 10, 40, 55, 70, 90, 135, 160% as the final strains. The scattering intensity distributions were not affected by these two conditions, while the affected intensities were not compared together.…”

The effect of MDI on the structure and mechanical properties of poly(lactic acid) and poly(butylene adipate-co-butylene terephthalate) blends

“…20 The presence of functional groups in polymer chains, giving rise to specic interactions with the blend constituent, can enhance the interfacial adhesion and phase dispersion, and improve the overall characteristics of the systems.…”