Impact of Strain-Induced Crystallization on Fast Crack Growth in Stretched cis-1,4-Polyisoprene Rubber

Abstract

cis-1,4-Polyisoprene (IR) elastomers harden via strain-induced crystallization (SIC) when the imposed stretch (λ) exceeds the onset value of SIC (λ*). We investigate the Mode-I fast crack growth in the IR sheets as a function of λ in a pure shear geometry. The steady-state crack velocity (V) increases with increasing λ, and V exceeds the shear wave speed of sound at λ > λs. Further stretch beyond λ* (>λs) causes SIC-driven hardening, resulting in a pronounced increase in V. The characteristics of the crack-tip strain field are also significantly influenced by the SIC-driven hardening: The crack-tip opening displacement increases with increasing λ at λ < λ* but exhibits an abrupt reduction beyond λ*. The crack-tip singularity and the area of strain increment caused by the crack growth change discontinuously around λ*. The abrupt variations in these crack-tip characteristics result from the considerable differences in the mechanical properties prior to the crack growth between the entirely amorphous state at λ < λ* and the partially crystallized state at λ > λ*.

Comparison of Mullins Effect Anisotropy of the Elastomers Reinforced by Carbon-Black and Silica Filler

“…In fact, the central area with a lateral length of approximately 100 mm undergoes the uniform planar stretching, which was shown in Fig. S3 in our previous study 43) . The unloaded sample was relaxed for 24 hours at 25 °C which was sufficiently long to equilibrate the strain recovery (Fig.…”

“…41, the SBR/Silica subsamples (SBR-Silica-0 and -90) were obtained by cutting out from the square sheet samples subjected to the planar stretching, in which one dimension remained unchanged during the stretching, using a biaxial tensile tester 41) . The present study employed the quasi-planar stretching geometry using a wide-width specimen, but the SBR/CB subsamples were cut out from the central area of the specimen satisfying the planar stretching 43) , allow- for SBR/Silica-0 and SBR/Silica-90, respectively. The data of SBR/Silica were reproduced from our previous study 41) .…”

Nanoparticle-Based Tough Polymers with Crack-Propagation Resistance

“…It is widely accepted that the tear test enables the understanding of the mechanical properties of materials in more detail via the use of notched specimens, and, thus, the tear test is one of the most reliable methods to evaluate the toughness of elastic materials , and even biological tissues . The analysis of crack propagation resistance gives an insight into the network structure and toughening mechanism of materials . Through a series of investigations, the effects of rotaxane crosslinking on toughed latex films is discussed.…”

On the influence of the amorphous phase on the stability of crystals in poly(cis‐1,4‐isoprene) networks

“…Crystals in natural rubber (NR) networks are a good example of this polymer‐typical characteristic, 5 because they form at room temperature only under strain but spontaneously melt when the stretching force is released and the rubber retracts back to its original dimensions. This phenomenon, referred to as strain‐induced crystallization (SIC), is intensively studied since its discovery in the 1920s, because it is assumed to be responsible for the outstanding high tensile strength of NR at high elongations 6–19 …”

“…This phenomenon, referred to as strain-induced crystallization (SIC), is intensively studied since its discovery in the 1920s, because it is assumed to be responsible for the outstanding high tensile strength of NR at high elongations. [6][7][8][9][10][11][12][13][14][15][16][17][18][19] Lately, an unusually lightly crosslinked variant of NR became known, which forms strain-induced crystals that do not vanish at room temperature. 20 Since a fraction of less than 20% strain-induced crystals retains the NR network in a highly elongated shape and it recovers its original shape not before these crystals are melted, it is referred to as shape memory natural rubber (SMNR).…”