Deformation Mechanisms of Semi-Crystalline Polymers on the Submicron Scale

Abstract

Micromechanical deformation mechanisms of two slightly branched polyethylenes have been studied by transmission electron microscopy and scanning force microscopy. Using an ethylene/hexene copolymer the transformation of the lamellar structure in the oriented structure inside a notch‐tip craze and using a binary blend of different ethylene/1‐hexene copolymers the deformation at elastomeric particles were investigated in detail. In particular, the micro‐block arrangement in lamellae and the transformation in structures like strings of beads have been studied using microscopy at higher magnifications.

Micromechanical modeling of elastic properties in polyolefins

“…In this work, the PP lamellae thickness is about 10 nm while the lamella thickness for HDPE is closer to 20 nm. Other authors [33] find the PE lamellae from 7 to 20 nm. Due to experimental difficulties, measurements of lamella length are scarce.…”

“…Considering for the PE lamellae, an average length from 0.5 to 1 mm as proposed by Michler and Godehardt [33], an average thickness of 20 nm [32] and a reasonably estimated width about 10 times the thickness, the calculated modulus overestimates largely the material modulus. As it has been discussed in Section 2, lamella shape ratios have not been defined precisely by experiments.…”

“…Due to experimental difficulties, measurements of lamella length are scarce. Authors have found only an estimate of the maximum length of PE lamellae in the range of 0.5 -1 mm [33]. Believing that spherulite size is related to the lamellae length [34], spherulite dimension has been measured in the core of the injection molded plates of PP and PE.…”

Structure of blown films of polyethylene/polybutene‐1 blends

“…The TEM investigation of the structure of the blends allowed us furthermore to gain information about the crystallization of both PE-LD and iPB-1. Figure 2 reveals formation of lamellae of typical thickness of 10-20 nm in the PE-LD matrix [33,34]. Because edge-on lamellae were detected in both the TD-ND plane and MD-ND plane, unequivocal conclusions about the orientation of PE-LD crystals cannot be drawn.…”

Plasticity of semi-crystalline polymers: crystal slip versus melting-recrystallization

“…To our knowledge, this is the only direct piece of evidence of strain-induced melting-recrystallization that has been ever reported. Further TEM studies from various authors [95][96][97][98] on semi-crystalline polymer thin films have mainly reported on the mechanisms of crazing and lamella fragmentation, with little interest if any to the occurrence of strain-induced melting-recrystallization.…”