Building a phenomenological chain-level understanding of mechanics of semicrystalline polymers: 1. Experimental

Smith, Travis; Gupta, Chaitanya; Siavoshani, Asal Y.; Wang, Shi‐Qing

doi:10.1016/j.polymer.2023.125878

Cited by 2 publications

(2 citation statements)

References 73 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This shift is supported by the WAXS results. Wang et al , have drawn a similar conclusion to ours in some semicrystalline polymers based on their drawability: a higher draw rate leads to the entangled chains acting as tie molecules, and it promotes the pull-out events in the crystalline phase, which is favorable to the drawability of the material.…”

Section: Discussionsupporting

confidence: 74%

Strain Rate Dependence of Amorphous Phase Instability in Semicrystalline Polymers: Insights from the Scale of Lamellar Stacks

Guo,

Zhu,

et al. 2024

Macromolecules

View full text Add to dashboard Cite

Given the structural hierarchy in semicrystalline polymers, there is a compelling need to elucidate the mechanisms behind the instability of the interlamellar amorphous phase at the scale of lamellar stacks, which constitute fundamental building units with a biphasic nature. We specifically chose a hard-elastic isotactic polypropylene film composed of highly oriented lamellar stacks as a model sample. By utilizing synchrotron-based in situ wide-, small-, and ultrasmall-angle X-ray scattering techniques (WAXS/SAXS/ USAXS), along with postmortem scanning electron microscopy (SEM) analysis, we studied the structural instabilities of lamellar stacks across a wide range of strain rates (from 0.001 to 0.5 s −1 ). Owing to the inherently dynamical asymmetry of the amorphous phase, we propose an insight into its instability characterized by stress-induced microphase separation based on the stress−concentration coupling model, where the extreme outcome aligns with the classical viewpoint, the formation of a fibrillar bridge/void system. With an increase in the Weissenberg number, a greater number of stress transmitters within the amorphous phase tend to be retained, thereby impeding the advancement of stress-induced microphase separation but promoting the crystalline phase instability. Furthermore, during the transition from a slow to a rapid stretching process, the amorphous phase instability undergoes a shift from a growth-dominated to a nucleation-dominated mode. This kinetic transition results in a more uniform dispersion of lamellar clusters that encompass unstable amorphous layers.

show abstract

Section: Discussionsupporting

confidence: 74%

Strain Rate Dependence of Amorphous Phase Instability in Semicrystalline Polymers: Insights from the Scale of Lamellar Stacks

Guo,

Zhu,

et al. 2024

Macromolecules

View full text Add to dashboard Cite

show abstract

“…Thus, a better understanding of fracture behavior is necessary and can promote the development of sustainable polymers and stimulate more efficient use of existing polymeric materials. In this context, an important topic is how to understand the brittle–ductile transition (BDT) in plastics − and how to apply the updated understanding − to make brittle polymers ductile through improved knowledge of the processing–structure–property relationship (P–S–P), e.g., through rheological manipulation of polymer structures. , We emphasize that the question of why plastics turn brittle upon temperature lowering is not a topic for fracture mechanics to investigate. Polymers in the plastic state are brittle because the underlying chain network breaks down before sufficient activation in the case of glassy polymers , or in the case of semicrystalline polymers before successful structural transformation, i.e., shape change of crystalline phases through adequate chain pull-out from the crystalline phases.…”

Section: Introductionmentioning

confidence: 99%

Fracture Behavior of Polymers in Plastic and Elastomeric States

Wang,

Fan,

Gupta

et al. 2024

Macromolecules

Self Cite

View full text Add to dashboard Cite

Our recent studies departed from the conventional description of polymer fracture behavior while maintaining consistency with the principles of material mechanics including linear elastic fracture mechanics (LEFM). In traditional fracture mechanics of brittle materials, crack resistance is quantified in terms of toughness G c , which represents the critical energy release per unit fracture surface area. This perspective suggests that high G c involved high energy dissipation. A new perspective has surfaced, proposing a fundamental yet underexplored, seemingly universal fracture mechanism and explaining the origin of high G c within an alternative framework. According to this view, for unfilled plastics and elastomers, f racture initiates when local tensile stress surpasses the polymer's f racture strength σ F(inh) , and high toughness is a consequence of high fracture strength. Remarkably, for polymers in both plastic and elastomeric states, their inherent strength σ F(inh) appears to be of a comparable magnitude to the nominal tensile strength σ b . Spatial−temporal resolved polarized optical microscopic (str-POM) measurements have started to provide insight into the fracture mechanism and unveil a concealed length scale (P) representing the size of a stress saturation zone at the crack tip. The two-parameter theoretical framework shows (a) toughness of brittle plastics increases quadratically with its strength σ F(inh) and linearly with P and (b) elastomers exhibit significantly greater toughness and higher tensile strength at lower temperatures due to the increased stability of covalent bonds given the lower thermal energy and plausible frictional effect on bond vibration frequency. Embracing this emerging paradigm where we recognize polymer strength to be time-dependent, we anticipate new advancements in polymer design and a clearer understanding of the fracture behavior of polymeric materials.

show abstract

Building a phenomenological chain-level understanding of mechanics of semicrystalline polymers: 1. Experimental

Cited by 2 publications

References 73 publications

Strain Rate Dependence of Amorphous Phase Instability in Semicrystalline Polymers: Insights from the Scale of Lamellar Stacks

Strain Rate Dependence of Amorphous Phase Instability in Semicrystalline Polymers: Insights from the Scale of Lamellar Stacks

Fracture Behavior of Polymers in Plastic and Elastomeric States

Contact Info

Product

Resources

About