Topological Mechanism of Polymer Nucleation and Growth – The Role of Chain Sliding Diffusion and Entanglement

Hikosaka, Masamichi; Watanabe, Kaori; Okada, Kiyoka; Yamazaki, Shinichi

doi:10.1007/12_010

Cited by 55 publications

(50 citation statements)

References 34 publications

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“…The influence of entanglements on nucleation density is in agreement with the earlier findings where Hikosaka and co-workers demonstrated that with the increasing entanglements, nucleation density decreases [12,13,14,15]. To recall, for their study the authors also created disentangled state but in a low molar mass high density polyethylene either by polymerization or by crystallizing the sample from melt in the hexagonal phase at high pressure and temperature.…”

Section: Crystallization In Heterogeneous Polymer Meltsupporting

confidence: 88%

“…The area-ratio between the low and the high melting temperature peaks changes with the annealing time of the melt at 160 °C. Considering the elastic shear modulus build-up with the annealing time at 160 °C and the corresponding transformation of the heterogeneous melt into homogeneous, the increase in the heat of fusion of the low melting temperature peak is attributed to the entangled state of the melt that causes increase in the nucleation barrier during isothermal crystallization [12,13,14,15] . 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 The absence of the prominent double-peak and the inversion process in the comparative commercial sample, Figure 2b, further strengthens the hypothesis that in the disentangled UHMWPE, the transformation of the heterogeneous distribution of entanglement density into homogeneous has an influence on the increase in the low temperature peak.…”

Section: Crystallization In Heterogeneous Polymer Meltmentioning

confidence: 99%

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Heterogeneous Distribution of Entanglements in a Nonequilibrium Polymer Melt of UHMWPE: Influence on Crystallization without and with Graphene Oxide

et al. 2016

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Recently, the influence of reduced graphene oxide nanoplatelets (rGON) on the rheological response of polymers has been a subject of interest. In the case of disentangled UHMWPE, it has been shown that the chain-filler interaction in the UHMWPE/rGON composite results into an everlasting non-equilibrium melt state having heterogeneous distribution in entanglement density. In this study, a thermal analysis protocol is used to follow the influence of the non-equilibrium polymer melt on the crystallization kinetics of disentangled UHMWPE with, and without, rGON. The analysis is carried out by means of differential scanning calorimetry (DSC) and the results are supported by rheology. When the disentangled UHMWPE sample, without the filler rGON, is left to crystallize under isothermal condition after melting, two endothermic peaks are observed: the high temperature peak (close to the equilibrium melting point, 141.5 °C) is related to the melting of crystals obtained on crystallization from the disentangled domains of the heterogeneous (nonequilibrium) polymer melt, whereas the low melting temperature peak is related to the melting of crystals formed from entangled domains of the melt. On increasing the annealing time in melt (160 °C), the enthalpy of the lower melting temperature peak increases at the expense of the high melting temperature peak, confirming a transformation of the nonequilibrium polymer melt to a fully entangled equilibrium melt state. However, independent of the equilibrium or non-equilibrium melt state, the recurrence of the high melting temperature peak is observed when the samples synthesized using the single-site catalytic system are left to isothermal crystallization at a specific temperature. The recurrence of the high melting temperature, close to the equilibrium melting point of the polymer, questions the differences in entanglements formed before and after polymerization in these high molar masses. The differences in the topological constraints are likely to influence the difference in melting temperatures of the isothermally crystallized samples. In the presence of rGON, the melting response of disentangled UHMWPE crystallized from its heterogeneous melt state changes; at a specific filler concentration, it is observed that the high endothermic peak remains independent of the annealing time in melt. This observation strengthens the concept that in the presence of the filler, chain dynamics is arrested to an extent that the nonequilibrium melt state having lower entanglement density is retained, facilitating the formation of crystals having high melting temperature. IntroductionThe topology of methylene segments in the non-crystalline region of the semi-crystalline polymer Ultrahigh Molecular Weight Polyethylene (UHMWPE), has a profound influence on the mechanical deformation either uniaxially or biaxially [1]. The topology can be tailored by controlling the crystallization kinetics either by dissolution and crystallization or controlled polymerization [2,3,4,5]. The influence of mo...

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Section: Crystallization In Heterogeneous Polymer Meltsupporting

confidence: 88%

Section: Crystallization In Heterogeneous Polymer Meltmentioning

confidence: 99%

Heterogeneous Distribution of Entanglements in a Nonequilibrium Polymer Melt of UHMWPE: Influence on Crystallization without and with Graphene Oxide

et al. 2016

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“…several polymers and it is plausibly explained by crystal thickening mechanism and sliding diffusion (e. g. [37]). Figure 6 shows that the values of long period changes significantly with deformation and these changes depend on the direction of measurements.…”

Section: Resultsmentioning

confidence: 99%

Cavitation during tensile drawing of annealed high density polyethylene

Pawlak

Gałęski

2010

Polymer

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The annealing of semicrystalline polymers usually leads to the crystal refinement and thickening. It appears that also the cavitation during tensile drawing is affected. In the uniaxially drawn high density polyethylene a massive cavitation was detected by X-ray scattering in samples previously annealed at 125 o C. The number of voids depends on the annealing time, while their size and orientation depends on the local strain. The cavitation resulted in 30% increase of volume for annealed samples, strained to 4-5. Cavitation and volume increase were not observed for small and intermediate strains if the polyethylene samples were not annealed. The decrease of drawing rate results in reducing cavitation and also the void stability: at the low strain rate voids were detected during tensile drawing but they disappeared after unloading the sample.

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“…More exactly, it is hardly a discriminating criterion when discussing the validity of crystallization schemes. Indeed, adjustment of lamellar thickness through thickening or thinning in the vicinity of the growth front (as observed for example in low molecular weight polyethylene oxide or long parafins, with ample longitudinal mobility along the chain axis 41 ) corresponds to a (admittedly early) postcrystallization mechanism. It does not reflect the details of the deposition process itself-except to point out that this deposition process is not an equilibrium one, at least as far as the lamellar thickness (or stem length) is concerned.…”

Section: Growth Of Twinned Crystalsmentioning

confidence: 99%

Polymer Crystallization Processes as Seen from the Growth Front’s Perspective

Lotz

Cheng

2008

Polym J

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A critical analysis is presented regarding the possible processes that determine polymer crystal growth, based mostly on the analysis of the structure and morphology of polymer single crystals. This ''forensic'' analysis suggests that the interaction of the depositing stem with the growth front is the determining factor in the whole crystallization process, irrespective of any previous (pre)organization process, be it spinodal decomposition, formation of ''smectic pearls'' or precursor phases followed by local reorganization. This conclusion stems from the analysis of the structure and morphology of polymer single crystals, from the recognition that bulk crystallization leads to similar structures of the lamellae that build up the spherulites, and from the distinctly different structures and morphologies of polymers for which a precursor phase (with either smectic or nematic order) has been recognized. The latter situation, with an intermediate loose pre-order, prevails for polymers with inherent chain rigidity.

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Topological Mechanism of Polymer Nucleation and Growth – The Role of Chain Sliding Diffusion and Entanglement

Cited by 55 publications

References 34 publications

Heterogeneous Distribution of Entanglements in a Nonequilibrium Polymer Melt of UHMWPE: Influence on Crystallization without and with Graphene Oxide

Heterogeneous Distribution of Entanglements in a Nonequilibrium Polymer Melt of UHMWPE: Influence on Crystallization without and with Graphene Oxide

Cavitation during tensile drawing of annealed high density polyethylene

Polymer Crystallization Processes as Seen from the Growth Front’s Perspective

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