Learning the deformation mechanism of poly(vinylidine fluoride-co-chlorotrifluoroethylene): an insight into strain-induced microstructure evolution via molecular dynamics

Abstract

Learning the micro-mechanisms of fluorinated polymers during mechanical response is more difficult than that of common polymers due to the unique intrinsic characteristics of the fluorine element. In this paper, we applied molecular dynamics simulations to study deformation mechanisms of poly(vinylidine fluoride-co-chlorotrifluoroethylene) during uniaxial tension. We analyzed the variations of individual energy components and structural distribution curves versus strain in addition to the commonly used stress-strain curves and microstructure evolutions during stretching. The elastic limit is ɛ = 0.02, ɛ = 0.06 is the yield point, ɛ = 0.24 is the termination of the softening, necking occurs at 0.24 < ɛ < 0.5, strain hardening occurs at 0.5 < ɛ < 2.6, and ɛ = 2.6 is the damage or brake point. The elastic behavior of the material does not rely on strain rate, the obvious effect of strain rate can be seen at the yield region and strain softening region, and the stress values are not influenced by strain rates at the softening and hardening stages. Overall, total potential energy is mainly correlated with non-bonded energy, and the proportion of ΔE overwhelms all the others. The energy components are ordered: ΔE > ΔE > > ΔE > ΔE > ΔE. The chain conformation at yield point is almost unchanged compared with the pre-stretching conformation. The chain conformations at the end of strain softening changes more obviously than that at yield point. The molecular chains maintain random coil structure before strain hardening, and switch into a stretch chain conformation gradually during strain hardening. The maximum change in bond angle during the stretching process is F-C-H, the largest change in bond length is the C-Cl bond, and the largest change in dihedral angle is H-C-C-H. The change of non-bonded interaction in the poly(VDF-co-CTFE) system is much larger than the bonding interaction, and the main factor affecting bonding interaction is the change of angles. Graphical abstract Poly(vinylidine fluoride-co-chlorotrifluoroethylene) during tensionᅟ.

Biomimetic nanoporous aerogels from branched aramid nanofibers combining high heat insulation and compressive strength

“…Ultimate strength at 80% strain shows a linear elastic deformation region ending at the strain of 2%, followed by a softening region where plastic deformation begins to occur. 82 After being compressed to 80% of its original length, the aerogel shows favorable toughness, without any cracks. The compressive energy could be absorbed by the strong three-dimensional network interconnection and contact points of nanofibers, leading to elastic deformation.…”

“…Branching also affects the shear stress–strain curve of BANF aerogel (Figure 8 and Table S4). Ultimate strength at 80% strain shows a linear elastic deformation region ending at the strain of 2%, followed by a softening region where plastic deformation begins to occur 82 . After being compressed to 80% of its original length, the aerogel shows favorable toughness, without any cracks.…”

Microscopic Mechanism of the Large Electrocaloric Effect in Vinylidene Difluoride-Based Polymers

“…The thermostat and barostat were both of Nosé–Hoover type . We used the polymer consistent force field (PCFF), which was previously successfully employed for modeling of poly­(VDF- ter -TrFE- ter -CFE) and poly­(VDF- ter -TrFE- ter -CTFE) terpolymers, poly­(VDF- co -CTFE) and poly­(VDF- co -HFP) copolymers (where HFP is hexafluoropropylene), as well as PVDF homopolymer − and poly­(vinyl chloride). , …”

Regulating the Crystallization Morphology of Poly(vinylidene fluoride‐chlorotrifluoroethylene) Ultrathin Film by Changing Temperature and Substrate

“…[23] This kind of P(VDF-CTFE) has excellent creep and adhesion properties, which is often used in coatings and adhesives. [24,25] The crystallization behavior of this kind of P(VDF-CTFE) has a significant effect on the mechanical strength and adhesion of their films. Chang et al [26] have proposed that the coexistence of crystalline and amorphous domains with different molecular chain mobility is the main reason for the strain rate dependence of mechanical response.…”

“…[ 23 ] This kind of P(VDF‐CTFE) has excellent creep and adhesion properties, which is often used in coatings and adhesives. [ 24,25 ] The crystallization behavior of this kind of P(VDF‐CTFE) has a significant effect on the mechanical strength and adhesion of their films. Chang et al.…”