Comparing elastomeric behavior of block and random ethylene–octene copolymers

Abstract

This work compared the elastomeric properties of two low-crystallinity ethylene-octene copolymers. One was a block copolymer with lamellar crystals and the other was a random copolymer with fringed micellar crystals. The comparison of the stress-strain behavior at 23 C revealed that the initial elastic modulus and the yield stress depended only on the crystallinity of the copolymer. When the temperature was raised above 23 C, melting of the fringed micellar crystals of the random copolymer caused a rapid decrease in the modulus. Some decrease in the modulus of the block copolymer over the same temperature range was attributed to the crystalline arelaxation. Both polymers exhibited strain-hardening, ultimate fracture at high strains, and high recovery after fracture. However, in the block copolymer, the onset of strain-hardening and the ultimate fracture occurred at higher strains. The block copolymer also showed higher recovery from high strains. The initial stretching resulted in a permanent change in the stress-strain curve. It was suggested that following the onset of crystal slippage at the yield, the crystals underwent permanent structural changes through the course of the strainhardening region. The transformation of the fringed micellar crystals occurred at lower strains than the transformation of the lamellar crystals. The extent of the structural transformation was described by the crosslink density and the strain-hardening coefficient extracted from elasticity theory.

Understanding the Formation of Linear Olefin Block Copolymers with Dynamic Monte Carlo Simulation

“…[1][2][3][4][5][6][7] OBCs have higher heat and abrasion resistances, and better processability than conventional polyolefin elastomers. [8][9][10][11] Because OBC may have many blocks, mathematical models are needed to quantify how polymerization conditions affect their microstructures. A detailed mathematical model describes how the complex OBC microstructure evolves during polymerization, providing useful insights on how to control these microstructures.…”

A Shish-kebab superstructure in low-crystallinity elastomer nanocomposites: Morphology regulation and load-transfer

“…As is described by A. Hiltner et al, the stress-strain behavior of OBC mainly consists of contributions from network junctions of two types, sliplinks and crosslinks. 5,7 Sliplinks are mobile networks junctions that restrict chain mobility at low strains (< 200%) until a sufficient force is applied, while crosslinks behave as permanent network junctions that primarily determine the slope of stress response at intermediate strains. 7 Sliplinks take place at strains below 200% and crystal lamellaes break down into smaller lamellaes; while when strains go beyond 300%, the smaller lamellaes begin to transform into an oriented fibrillar morphology.…”

“…1,2 With densely research in mesophase separation, block architecture and elastomeric properties, OBC affirmably exhibits different microdomain structure, network effectiveness and mechanical properties from ORCs. [3][4][5][6][7][8][9] Presenting large industrial potential, OBCs still have shortcomings such as unsatisfying tensile strength and Young's modulus due to their low crystallinity. Yet, no work on the morphology and properties of filled OBC systems has been reported.…”

Morphology and mechanical properties of poly(ethyleneoctene) copolymers obtained by dynamic packing injection molding

“…Effect of uniaxial deformation on crystal behavior was carefully studied and resulted in typical changes of phase structure and crystal morphology [9−11] . Wang et al [12] investigated the elastomeric behavior and found transformation of fringed micellar crystals occurred at different strains. When POE is grafted with other molecules, it could also be used as compatablizers for different polymer blends [13,14] .…”