Investigation of Crystallization and Relaxation Effects in Coarse-Grained Polyethylene Systems after Uniaxial Stretching

Grommes, Dirk; Schenk, Martin; Bruch, Olaf; Reith, Dirk

doi:10.3390/polym13244466

Cited by 4 publications

(19 citation statements)

References 41 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We equilibrate and further investigate four different system sizes with various numbers of chains M and chain length N (

). Our equilibrated systems have density of the amorphous phase at 293 K (

), melt density (

), coefficient of thermal expansion (CTE), glass transition temperature (

) and crystallization onset temperature (

) in good agreement with experimental results [ 24 ].…”

Section: Simulation Methodologysupporting

confidence: 72%

“…We use a coarse-grained polyethylene force field [ 28 ] which we previously utilized to simulate tensile tests [ 29 ] and relaxation effects in uniaxially stretched systems [ 24 ]. It was shown that it is suitable for evaluating entanglement, orientation and crystallization effects that drive the behavior of polyethylene.…”

Section: Simulation Methodologymentioning

confidence: 99%

“…Based on the formulation of the nematic order parameter, we calculate the uniaxial orientation factor

as follows: (a) determination of the local bond vector orientation factor

in longitudinal stretching direction as already introduced in [ 24 ]; (b) determination of the corresponding orientation factor

in perpendicular direction; (c) the uniaxial orientation factor is

. This definition gives an estimate to what extent systems are uniaxially (

) or (equi-)biaxially (

) oriented, respectively.…”

Section: Simulation Methodologymentioning

confidence: 99%

“…This relation allows for an estimate of how entangled the systems with different chain lengths are. Further details concerning the use of the PPA with respect to our systems are given in [ 24 ].…”

Section: Simulation Methodologymentioning

confidence: 99%

“…These studies focus on uniaxially stretched or sheared systems only. In our previous work [ 24 ], we investigated uniaxially stretched polyethylene systems’ crystallization and relaxation behavior at one specific level of stretching

. As real-life processes usually introduce biaxial stretching to the processed melt, drastically changing trends of chain straightening and orientation are likely to occur [ 25 ].…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Initial Crystallization Effects in Coarse-Grained Polyethylene Systems After Uni- and Biaxial Stretching in Blow-Molding Cooling Scenarios

et al. 2022

Self Cite

View full text Add to dashboard Cite

This study investigates the initial stage of the thermo-mechanical crystallization behavior for uni- and biaxially stretched polyethylene. The models are based on a mesoscale molecular dynamics approach. We take constraints that occur in real-life polymer processing into account, especially with respect to the blowing stage of the extrusion blow-molding process. For this purpose, we deform our systems using a wide range of stretching levels before they are quenched. We discuss the effects of the stretching procedures on the micro-mechanical state of the systems, characterized by entanglement behavior and nematic ordering of chain segments. For the cooling stage, we use two different approaches which allow for free or hindered shrinkage, respectively. During cooling, crystallization kinetics are monitored: We precisely evaluate how the interplay of chain length, temperature, local entanglements and orientation of chain segments influence crystallization behavior. Our models reveal that the main stretching direction dominates microscopic states of the different systems. We are able to show that crystallization mainly depends on the (dis-)entanglement behavior. Nematic ordering plays a secondary role.

show abstract

“…We equilibrate and further investigate four different system sizes with various numbers of chains M and chain length N (

). Our equilibrated systems have density of the amorphous phase at 293 K (

), melt density (

), coefficient of thermal expansion (CTE), glass transition temperature (

) and crystallization onset temperature (

) in good agreement with experimental results [ 24 ].…”

Section: Simulation Methodologysupporting

confidence: 72%

Section: Simulation Methodologymentioning

confidence: 99%

“…Based on the formulation of the nematic order parameter, we calculate the uniaxial orientation factor

as follows: (a) determination of the local bond vector orientation factor

in longitudinal stretching direction as already introduced in [ 24 ]; (b) determination of the corresponding orientation factor

in perpendicular direction; (c) the uniaxial orientation factor is

. This definition gives an estimate to what extent systems are uniaxially (

) or (equi-)biaxially (

) oriented, respectively.…”

Section: Simulation Methodologymentioning

confidence: 99%

Section: Simulation Methodologymentioning

confidence: 99%

. As real-life processes usually introduce biaxial stretching to the processed melt, drastically changing trends of chain straightening and orientation are likely to occur [ 25 ].…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Initial Crystallization Effects in Coarse-Grained Polyethylene Systems After Uni- and Biaxial Stretching in Blow-Molding Cooling Scenarios

et al. 2022

Self Cite

View full text Add to dashboard Cite

show abstract

Insights into the solubility of H2 in various polyethylene matrices at high pressure: A coarse-grained MC/MD study

Zhao

Wang

et al. 2023

International Journal of Hydrogen Energy

View full text Add to dashboard Cite

Hop, Skip, and Jump: Hydrogen Molecular Transport through Amorphous Polyethylene Matrices Studied via Molecular Dynamics Simulations

Divine-Ayela,

Perez,

Striolo

2023

Ind. Eng. Chem. Res.

View full text Add to dashboard Cite

In the pursuit of advancing and diversifying energy technologies for a more sustainable future, the possibilities of hydrogen (H 2 ) usage will broaden, as will our understanding of its containment materials. Polyethylene (PE) has a vast assortment of uses and applications, which are growing with demands for alternative energy possibilities. One use of PE liner is as a prime candidate for nonmetallic piping and pressurized type IV storage devices. Such applications require PE to effectively prevent H 2 transport through containment systems. To study the molecular transport mechanism of hydrogen through polymeric barriers, a system containing hydrogen molecules absorbed within amorphous PE is modeled here using molecular dynamics simulations. The simulations are conducted within a range of temperatures that span the glass transition temperature of amorphous PE. The simulated PE displays bulk density, radius of gyration, and self-diffusion coefficient that are consistent with experimental data. The simulated trajectories are interrogated to study the movement of the guest gas molecules. The results show that the diffusion coefficients increase with temperature, as expected. However, the mobility of the PE chains is found to affect the mobility of absorbed H 2 molecules to a much lower extent than it affects that of CH 4 molecules because of the much smaller size of the former than of the latter guest. From a molecular perspective, a "hopping" mechanism is observed, according to which H 2 molecules hop between one vacant free volume space to another within the polymer matrix, in combination with longer, straight, undisturbed "jumps" or "skips" along directions aligned with regions of ordered PE chains. This suggests that the orientation of the crystallites within the semicrystalline PE matrix affects the H 2 containment. Implications of these findings toward PE usage as containment material are discussed.

show abstract

Investigation of Crystallization and Relaxation Effects in Coarse-Grained Polyethylene Systems after Uniaxial Stretching

Cited by 4 publications

References 41 publications

Initial Crystallization Effects in Coarse-Grained Polyethylene Systems After Uni- and Biaxial Stretching in Blow-Molding Cooling Scenarios

Initial Crystallization Effects in Coarse-Grained Polyethylene Systems After Uni- and Biaxial Stretching in Blow-Molding Cooling Scenarios

Insights into the solubility of H2 in various polyethylene matrices at high pressure: A coarse-grained MC/MD study

Hop, Skip, and Jump: Hydrogen Molecular Transport through Amorphous Polyethylene Matrices Studied via Molecular Dynamics Simulations

Contact Info

Product

Resources

About