Distribution of molecular weights and branching of high‐density polyethylene

Agarwal, Rakesh; Horská, Jitka; Stejskal, Jaroslav; Quadrat, O.; Kratochvı́l, Pavel; Hudec, Pavel

doi:10.1002/app.1983.070281111

Cited by 18 publications

(7 citation statements)

References 41 publications

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“…As soon as substantial polydispersity is introduced, the number of variables also rises (think of the set of moments of the molecular weight distribution). Accurate values of the moments higher than the third are notoriously hard to acquire [82], even if a theory is sophisticated enough to account for them in a predictive way. It is far better to work with materials in which the polydispersity is reduced to a perturbative quantity.…”

Section: Chemical Synthesis Of Controlled Topologiesmentioning

confidence: 99%

Tube theory of entangled polymer dynamics

McLeish

2002

Advances in Physics

838

1,122

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The dynamics of entangled¯exible polymers is dominated by physics general to many chemical systems. It is an appealing interdisciplinary ®eld where experimental and theoretical physics can work closely with chemistry and chemical engineering. The role of topological interactions is particularly important, and has given rise to a successful theoretical framework: the`tube model'. Progress over the last 30 years is reviewed in the light of specially-synthesized model materials, an increasing palette of experimental techniques, simulation and both linear and nonlinear rheological response. Our current understanding of a series of processes in entangled dynamics:`reptation',`contour length¯uctuation' and`constraintrelease' are set in the context of remaining serious challenges. Especial attention is paid to the phenomena associated with polymers of complex topology or`long chain branching'.

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Section: Chemical Synthesis Of Controlled Topologiesmentioning

confidence: 99%

Tube theory of entangled polymer dynamics

McLeish

2002

Advances in Physics

838

1,122

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“…SEC [gel permeation chromatography (GPC)] has widely found applications as an indirect/relative technique for characterizing MWD in polymers. It reveals the molecular weight of a polymer fraction by the detection of its hydrodynamic volume27–30 [which is given as the product of the intrinsic viscosity ([η]) and viscosity‐average molecular weight] by comparison with a calibration curve of standard polymers of known MWD. By the measurement of [η] with an inline viscometer and refractive‐index detector, the viscosity‐average molecular weight of the polymer fraction can be readily calculated 28, 29…”

Section: Determination Of the Branch Content In Polymers By Secmentioning

confidence: 99%

Distinct expression of TRPM8, TRPA1, and TRPV1 mRNAs in rat primary afferent neurons with aδ/c‐fibers and colocalization with trk receptors

Kobayashi,

Fukuoka,

Obata

et al. 2005

J of Comparative Neurology

688

552

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The transient receptor potential (TRP) superfamily of cation channels contains four temperature-sensitive channels, named TRPV1-4, that are activated by heat stimuli from warm to that in the noxious range. Recently, two other members of this superfamily, TRPA1 and TRPM8, have been cloned and characterized as possible candidates for cold transducers in primary afferent neurons. Using in situ hybridization histochemistry and immunohistochemistry, we characterized the precise distribution of TRPA1, TRPM8, and TRPV1 mRNAs in the rat dorsal root ganglion (DRG) and trigeminal ganglion (TG) neurons. In the DRG, TRPM8 mRNA was not expressed in the TRPV1-expressing neuronal population, whereas TRPA1 mRNA was only seen in some neurons in this population. Both A-fiber and C-fiber neurons expressed TRPM8, whereas TRPV1 was almost exclusively seen in C-fiber neurons. All TRPM8-expressing neurons also expressed TrkA, whereas the expression of TRPV1 and TRPA1 was independent of TrkA expression. None of these three TRP channels were coexpressed with TrkB or TrkC. The TRPM8-expressing neurons were more abundant in the TG compared with the DRG, especially in the mandibular nerve region innervating the tongue. Our data suggest heterogeneity of TRPM8 and TRPA1 expression by subpopulations of primary afferent neurons, which may result in the difference of cold-sensitive primary afferent neurons in sensitivity to chemicals such as menthol and capsaicin and nerve growth factor.

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“…[7] When the LCB content is very low (less than 1 LCB /10 4 C), its effect on the radius of gyration goes unnoticed and values of g ≈ 1 are obtained [42]. The effect of such a low amount of LCB has been explored in LDPE and in modified linear polymers of ethylene/α-olefins and propylene (PP) by irradiation, electron-beam treatment, peroxide reaction, and thermal/mechanical degradation [7,10,17,[44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59]. In principle, lowpressure processes (chromium-based and Ziegler-Natta type catalysts, developed in the 1950s and 1970s, respectively) yield linear species.…”

Section: Conventional Polymersmentioning

confidence: 99%

Effect of long chain branching on linear-viscoelastic melt properties of polyolefins

et al. 2002

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Abstract:The aim of this review is to provide evidence that rheological testing is a potent tool for characterising polymers in the melt. An effort has been made in order to gather results in conventional and model polyolefins, and correlating them with phenomena occurring at the molecular level. We have focused our interest on long chain branching (LCB). In the case of materials containing long side-chain branches, strong effects on viscosity, elastic character and activation energy of flow are general features. Literature results mostly indicate that the effect of polydispersity on these parameters could be very similar to that expected due to the presence of LCB -notwithstanding that the effects of LCB seem to be stronger than those due to polydispersity for a given molecular weight. Different relaxation processes appear as a consequence of the presence of LCB: slower terminal relaxation behaviour than of linear counterparts, and faster additional branch relaxation at higher frequencies, clearly distinguishable from polydispersity effects. To measure the amount of LCB from limited viscoelastic data and molecular properties seems to be a suitable instrument to explain the rheological features of the different polymers, but it fails when the results are compared with measured values of LCB density in model polymers. The actual framework leads us to say that the number of branches is less important than the topology itself. Therefore, the position and architecture of the branches along the polymer main chain are the main factors that control the rheology of the material.

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Distribution of molecular weights and branching of high‐density polyethylene

Cited by 18 publications

References 41 publications

Tube theory of entangled polymer dynamics

Tube theory of entangled polymer dynamics

Distinct expression of TRPM8, TRPA1, and TRPV1 mRNAs in rat primary afferent neurons with aδ/c‐fibers and colocalization with trk receptors

Effect of long chain branching on linear-viscoelastic melt properties of polyolefins

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