Precursor formation and crystal nucleation in stretched polyethylene/carbon nanotube nanocomposites

Molecular Details of the “Catalytic Effect” of Long Chains on Short Chains in Stretch-Induced Polymer Crystallization

“…For comparison, the values of the P of bonds in the short-chain system are also shown. The values of the P of bonds along the stretching direction were calculated based on the following equation: P = ⟨ 3 cos 2 true( φ i true) − 1 2 ⟩ = 3 2 ⟨ ( bolde i → . bolde normals ) 2 ⟩ − 1 2 where e i is the unit vector of the polymer bond located at the i th bead (the vector from bead i – 1 to bead i + 1), e s is the unit vector along the stretching direction, φ i is the angle enclosed by e i and e s , and ⟨⟩ indicates the statistical average of the calculated values for the bonds. − The value of P can be applied to reflect the degree of orientation of the polymer bonds. It can be seen in Figure that the values of the P of the long-chain bonds in the blended systems with higher contents of the long chains are higher than those of the short-chain bonds at the same strains in the strain region of strain less than 2.0.…”

“…In our previous work, we found that stretching can induce the orientation of carbon nanotubes (CNTs) along the stretching direction, which can then induce the local orientation of interfacial chain segments along the axes of CNTs. 41 Under the influence of the interfacial interactions between CNTs and polymer segments, CNTs that are more prone to orientation in the stretching process will drive the orientation of polymer segments in interfacial regions. 41 In the current simulations, to reveal the relationship between the interactions between the long-chain and the short-chain bonds and the induced orientation effects of long-chain segments on neighboring short-chain segments, we calculated the evolutions of the Lennard-Jones (LJ) potential energy between the longchain bonds with a high orientation degree of bonds (P ≥ 0.9) at a strain of 2 and their neighboring short-chain bonds also with a high orientation degree (P ≥ 0.9) at a strain of 2 during stretching prior to the occurrence of strain-induced crystallization, as shown in Figure 9a.…”

Preparation, stretch‐induced crystallization and thermo‐oxidative aging behavior of poly (lactic acid)/saponite grafted polystyrene nanocomposites films

“…When the traction ratio was increased to 24, the elongation at break of the PLA0 film was increased from 25.8% to 36.7%, while the elongation at break of PLA3 film was increased from 81.2% to 135.5%. Compared with PLA0 film, the PLA3 film presented higher mechanical properties, thus was attributed to the synergistic action of tensile deformation and modified saponite, where tensile deformation induced homogeneous nucleation, which improved the regularity of the PLA molecular chains, while the presence of the tensile flow field was more conducive to the homogeneous distribution of nanoparticles to achieve a better mass and heat transfer, while modified saponite exerted heterogeneous nucleation, which improved the orientation of PLA 40 …”

“…Compared with PLA0 film, the PLA3 film presented higher mechanical properties, thus was attributed to the synergistic action of tensile deformation and modified saponite, where tensile deformation induced homogeneous nucleation, which improved the regularity of the PLA molecular chains, while the presence of the tensile flow field was more conducive to the homogeneous distribution of nanoparticles to achieve a better mass and heat transfer, while modified saponite exerted heterogeneous nucleation, which improved the orientation of PLA. 40 Figure 12 showed the DSC curves of pure PLA film and PLA3 film at different traction ratios for a single temperature rise. From Figure 12, it could be seen that the cold crystallization temperature of PLA3 film was lower and the area of the cold crystallization peaks was smaller compared with PLA0 film.…”

Fundamentals of Crystalline Evolution and Properties of Carbon Nanotube-Reinforced Polyether Ether Ketone Nanocomposites in Fused Filament Fabrication

“…However, these methods are incapable of capturing molecular interactions at the atomic scale. Using molecular dynamics (MD) simulations, several studies have reported the formation of organized chain structures around the CNTs for polyimide and polyethylene matrices. , Exploring the atomic scale changes in the matrix surrounding the CNTs is essential to understand the molecular mechanisms, which will aid in controlling material properties. It should be noted that PEEK and its nanocomposites exhibit hierarchical structures with a characteristic length scale of several microns .…”