Molecular weight dependence of lateral growth rate of polyethylene (I) — an extended chain single crystal

Nishi, Mutsuo; Hikosaka, Masamichi; Toda, Akihiko; Takahashi, Masato

doi:10.1016/s0032-3861(97)00488-6

Cited by 17 publications

(14 citation statements)

References 14 publications

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“…is confirmed. Also, log I 0 vs log M n for the disordered phase (ECSCs) is shown as a reference in Figure , which is re-plotted from ref . Thus, it is concluded that the power law of I is confirmed both for FCSCs and ECSCs.…”

Section: Resultssupporting

confidence: 56%

“…Comparison of the Experimental Facts with the Sliding Diffusion Theory of Nucleation. The observed power law can be well explained by the chain sliding diffusion theory of nucleation proposed in the previous paper . The theory formulated where α is a kind of order parameter related to the degree of order of the crystalline phase.…”

Section: Discussionsupporting

confidence: 54%

“…The best fit line for FCSCs show a power law, I ∝ M n -2.4 . The result for ECSCs is re-plotted for comparison from ref . …”

Section: Resultsmentioning

confidence: 99%

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Power Law of Molecular Weight of the Nucleation Rate of Folded Chain Crystals of Polyethylene

et al. 2002

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The molecular weight (Mn) dependence of the primary nucleation rate (I) of folded chain single crystals (FCSCs) of polyethylene (PE) was studied. A power law for the nucleation rate, I ∝ Mn -2.4 , was found. The FCSCs were formed by isothermal crystallization from the melt into an ordered phase ()orthorhombic phase). A new experimental method was established to obtain reliable I, which has been difficult in the case of heterogeneous nucleation for long years. The degree of supercooling (∆T) dependence of I fits well with the theoretical I given by classical nucleation theory, I ) I0 exp(-∆G*/kT) ∝ D exp(-C/∆T 2 ), where I0 is proportional to the topological diffusion coefficient of polymer chains (D), ∆G* is the free energy for forming a critical nucleus, k is the Boltzmann constant, T is temperature, and C is a constant. It is found that ∆G* (∝C) does not depend on Mn, while I0 decreases with increase of Mn, from which it is concluded that formation of a critical nucleus is not controlled by Mn, while only topological diffusion of polymers is controlled by Mn, i.e., I ∝ D(Mn). Similar power laws of PE were already found by the present authors on I of extended chain single crystals (ECSCs), i.e., I ∝ Mn -1.0 , and on the lateral growth rates (V) of ECSCs and FCSCs, V ∝ Mn -0.7 and V ∝ Mn -1.7 , respectively. ECSCs were formed by isothermal crystallization from the melt into a disordered phase ()hexagonal phase). Therefore, it is concluded that a common power law, I, V ∝ D(Mn) ∝ Mn -H of PE is confirmed, irrespective of nucleation or growth and irrespective of crystalline phases, ordered or disordered phases. It is to be noted that the power H depends on the degree of order of the crystalline phase, from which it is concluded that both nucleation and growth are controlled by the "topological" diffusion of polymer chains within interface between a nucleus (or crystal) and the melt and/or within the nucleus. The "topological" diffusion is related to chain sliding diffusion and disentanglements.

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Section: Resultssupporting

confidence: 56%

Section: Discussionsupporting

confidence: 54%

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Power Law of Molecular Weight of the Nucleation Rate of Folded Chain Crystals of Polyethylene

et al. 2002

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“…This can be attributed to the lower MWDs of the hexene comonomer resins, thus a greater proportion of highly crystallizable molecular segments and greater regularity in crystalline structures. Additionally, the reduction in crystallinity as M w increases for hexene mLLDPE films is supported by previous authors [8][9][10], who described a general reduction in crystallinity due to increased molecular entanglements, reduced chain mobility, and a lower rate of chain segregation. It has also been observed that film web width decreases with increase in M w , due to increases in extensional viscosity.…”

Section: Crystallinitysupporting

confidence: 72%

The Effect of Polymer Properties on the Mechanical Behavior and Morphological Characteristics of Cast Polyethylene Film for Stretch and Cling Film Applications

Mcnally

Small

Murphy

et al. 2005

Journal of Plastic Film & Sheeting

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Polyethylene films, prepared from a range of mLLDPE, LLDPE, and ULDPE resins containing 4% polyisobutylene (PIB) from a masterbatch, are manufactured using a Killion cast film extrusion system. FTIR, DSC, and mechanical analysis techniques are used to investigate the effect of comonomer type, density, and melt flow index (MFI) on the mechanical performance, orientation, and crystallinity of these films. The study established that comonomer type and MFI are the greatest factors influencing the mechanical performance and crystallinity. Crystallinity has been found to be the most influential factor governing PIB migration in these films and this in turn is related to polymer type, density, and MFI.

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“…As to the M dependence of the lateral growth rate( V), we have already shown in the previous papers 11 • 12 that Voc.M-H where His a constant ( Figure I). We named it "power law of the lateral growth."…”

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confidence: 82%

Molecular Weight Dependence of Primary Nucleation Rate of Polyethylene I. An Extended Chain Single Crystal

Nishi

Hikosaka

Ghosh

et al. 1999

Polym J

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ABSTRACT:Molecular weight (M) dependence of the primary nucleation rate (I) of an extended chain single crystal of polyethylene crystallized at high pressure (P=0.4 GPa) was studied. We obtained for the first time an experimental formula that 1rxM-1 which we named "power law of primary nucleation". We showed a well-known experimental formula that I= 10 exp( -K/11T 2 ), where IO is a constant proportional to the diffusion constant of molecules (D), K is related to the activation free energy for forming a critical nucleus (!:iG*) and l:!.T is the degree of supercooling. We showed that only / 0 rxD decreases with increase in Mand K does not depend on M. From this results we concluded that M dependence of I is mainly controlled by the "chain sliding diffusion" process not by the formation process of a critical nucleus, that is, l(M) rxD(M)rxP,(M) and l:!.G* =const. Here D can be regarded as an "expanded diffusion constant" and P, is a survival probability defined in "chain sliding diffusion" theory presented before by one of authors (MH). Based on these results we proposed a "chain sliding diffusion theory of primary nucleation" that the primary nucleation is a process of "chain sliding diffusion" within the nucleus which requires disentanglement of molecular chains within the interface between the nucleus and the melt. The theory explained well the observed power law.KEY WORDS Nucleation / Nucleation Rate/ Molecular Weight /Polyethylene/ Power Law / Sliding Diffusion/ Primary nucleation is important onset stage 1 in crystallization of materials from an isotropic phase, such as the melt, the solution, gas and amorphous solid or from other phases, such as liquid crystalline one. The primary nucleation mechanism of atomic or low molecular weight systems has been studied well, 2 -5 while that of polymers has not been studied well and has been left unsolved for long years. 6 -10 (FCC and ECC), that is H = 1.8 and 0. 7 for FCC and for ECC, respectively. From this result, it is concluded that chain sliding diffusion on the interface between the melt and crystal controls the M dependence of the V (Figure 2). Another purpose of this work is to make clear if the "power law" can be also found in M dependence of nucleation rate or not.It is obvious that the molecular weight (M) is one of the most important parameters of poymer systems and it has been well known that M strongly affects the nucleation process of polymers, which strongly controls the crystallization behaviors. But the M dependence of polymer nucleation has not been studied well as far as authors' knowledge, therefore the mechanism of it has not been solved at all, although it is very interesting and important for both polymer science and technology to solve it.The main purpose of this work is to show a reliable experimental formula of M dependence of the primary nucleation rate (I) of polyethylene (PE) for the first time and to propose a new mechanism of the M dependence of the primary nucleation which we will name "chain sliding diffusion theory of primary nu...

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Molecular weight dependence of lateral growth rate of polyethylene (I) — an extended chain single crystal

Cited by 17 publications

References 14 publications

Power Law of Molecular Weight of the Nucleation Rate of Folded Chain Crystals of Polyethylene

Power Law of Molecular Weight of the Nucleation Rate of Folded Chain Crystals of Polyethylene

The Effect of Polymer Properties on the Mechanical Behavior and Morphological Characteristics of Cast Polyethylene Film for Stretch and Cling Film Applications

Molecular Weight Dependence of Primary Nucleation Rate of Polyethylene I. An Extended Chain Single Crystal

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