Branching and flow activation‐energy of conventional high pressure process polyethylene

Nakajima, Nobuyuki; Tirpak, G. A.; Shida, Mitsuzo

doi:10.1002/pol.1965.110031223

Cited by 11 publications

(2 citation statements)

References 4 publications

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“…This indicates that the energy barrier for chain motion in the melt decreases with both the backbone rigidity and the side chain bulkiness. This is another anomalous behavior, considering that flow activation energy of amorphous polymers is an increasing function of side group size in essentially linear polymers, and of the degree of branching in long‐chain‐branched polymers . Similar to the anomalous dependence of the fragility discussed above, this behavior can be rationalized by the microstructure of these polymers, as discussed below.…”

Section: Results and Discusionmentioning

confidence: 77%

Dynamic Fragility of α‐Olefin Molecular Bottlebrushes

López‐Barrón

Hagadorn

2019

J Polym Sci B Polym Phys

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The glass transition temperature, dynamic fragilities, and flow activation energy of a series of well-entangled poly(α-olefin) (PαO) molecular bottlebrushes were measured as a function of side chain length (N sc ). The PαO bottlebrushes studied here have side chain lengths, N sc , ranging from 4 (poly(1-hexene)) to 10 (poly (1-dodecene). A linear polyolefin (polypropylene), with Nsc = 1, was included in this study as a reference. The observed glassy dynamics behavior in the PαO bottlebrushes is opposite to that observed in linear polymers, namely, the glass transition temperature, the dynamic fragility, and the activation energy of structural relaxation are decreasing functions of the backbone rigidity. This anomalous behavior is due to a decrease in correlation between adjacent backbones, which is directly related to their cooperativity in the α-relaxation, as N sc and the concomitant distance between backbones increase. This change in conformation is also manifested as an increase in free volume and the consequent decrease in monomeric friction coefficient.

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Section: Results and Discusionmentioning

confidence: 77%

Dynamic Fragility of α‐Olefin Molecular Bottlebrushes

López‐Barrón

Hagadorn

2019

J Polym Sci B Polym Phys

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“…This interpretation would appear to contradict the generally accepted interpretation that the high melt flow activation energy for high pressure polyethylene is ascribed to the existence of long-chain branching13$29?30). However, it seems to be rather relevant idea as suggested by NAKAJIMA et al 31) t h a t in case of high pressure polyethylene the complicated cluster of shortchain branchings might cause the elevation of the activation energy. Taking account of the unusual behaviour of polyhexene-1 in the yj' us.…”

Section: Podmentioning

confidence: 98%

Rheological properties of poly‐α‐olefin melts

1971

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I n order to investigate the influence of the side-chain length on the melt viscoelasticity of the hydrocarbon polymers, dynamic viscosity q', dynamic rigidity G' and apparent viscosity qa of a series of six different poly-cc-olefins have been measured with a rotating cylinder-type rheometer.The molecular weight dependence of q' and qa was relatively greater a t lower shear rate. Affixed shear rate and temperature, q', G', and qa for each polymer sample were expressed by the form of KRg. The values of K decreased with increasing side-chain length and the values of cc were approximately 3-4 for all the samples studied.curves at different temp. (130-230°C) could be superposed according to the usual time-temperature superposition method, and the shift factors aT obtained from q' , G', and qa were practically the same.The flow activation energies obtained from aT first increased with increasing side-chain length in going from polyethylene to polyhexene-1, and thereafter decreased in going from polyhexene-1 to polyoctadecene-1. They were all lower than that of high pressure polyethylene.These results appear t o support the idea that the branching structure of high pressure polyethylene is much more complicated than the side-chain structure of poly-a-olefins. q' us. w, G' us. w and qa us. ZUSAMMENFASSUNG:Mit einem Rotationszylinder-Rheometer wurden die dynamische Viskositat q', der dynamische Elastizitatsmodul G' und die scheinbare Viskositat qa fur eine Reihe von sechsPoly-cc-olefinen gemessen, um den Einflul3 der Lange der Seitenketten auf die Schmelzviskoelastizitat der Kohlenwasserstoffpolymeren zu untersuchen.Die Molekulargewichtsabhangigkeiten von q' und qa waren verhaltnismafiig starker bei niedriger Schergeschwindigkeit. Bei bestimmter Schergeschwindigkeit und Temperatur wurden q', G' und qa fur jede Polymerprobe durch die Form KmE dargestellt. Die K-Werte nahmen mit wachsender Seitenkettenlange ab. a hatte bei allen untersuchten Proben Werte von annahernd 3 bis 4.Die graphische Darstellung von q' gegen w, G' gegen w und qa gegen f bei verschiedenen Temp. (130-230°C) konnte durch gewohnliche Zeit-Temperatur-Superpositionsverfahren ermittelt werden, wobei die aus q', G' und qa erhaltenen Verschiebnngsfaktoren aT beinahe gleich waren.Die scheinbare Aktivierungsenergie des viskosen Flieaens, die aus dem Verschiebungsfaktor aT erhalteu wurde, nahm mit wachsender Seitenkettenlange von Polyathylen bis Polyhexen-l zu und von Polyhexen-1 bis Polyoktadecen-1 ab, und sie war niedriger als diejenige von Hochdruck-Polyathylenen.Diese Ergebnisse scheinen die Vorstellung zu unterstutzen, dafi die Verzweigungsstruktur der Hochdruck-Polyathylene vie1 komplizierter ist als die Seitenkettenstrnktur der Poly-cc-olefine. 155

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Influence de la température sur i'écoulement des polymères. Correlation pratique et mathématique de i'énergie d'activation de i'écoulement pour le polyéthylène basse‐densité, polyéthylène haute‐densité, polystyrène et d'autres polyoléfines

Deri¹,

Al-Deyab²,

Majid³

1989

Angew. Makromol. Chem.

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RESUME:Nous avons etudie les propriktes rheologiques des materiaux A l'etat fondu au moyen d'un viscosimetre A capillaire.Nous avons essay6 de relier les valeurs des energies d'activation, a vitesse et tension de cisaillement constantes, avec les valeurs de l'indice d'ecoulement .Les valeurs de l'indice d'ecoulement obtenues selon l'approche mathkmatique ne coincident pas avec les valeurs obtenues experimentalement. L'energie d'activation de LDPE est superieure a celle du HDPE en raison du volume libre de LDPE qui est plus grand. SUMMARY:The behaviour of materials has been studied in molten state. Measurements were made by a capillary viscometer. We have tried to link the values of activation energy at constant shear rate and a constant shear stress with the values of melt flow.The values of melt flow obtained according to the mathematical approach do not coincide with the values obtained experimentally. The activation energy of LDPE is superior to that of HDPE on account of the free volume of LDPE which is greater.

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Branching and flow activation‐energy of conventional high pressure process polyethylene

Cited by 11 publications

References 4 publications

Dynamic Fragility of α‐Olefin Molecular Bottlebrushes

Dynamic Fragility of α‐Olefin Molecular Bottlebrushes

Rheological properties of poly‐α‐olefin melts

Influence de la température sur i'écoulement des polymères. Correlation pratique et mathématique de i'énergie d'activation de i'écoulement pour le polyéthylène basse‐densité, polyéthylène haute‐densité, polystyrène et d'autres polyoléfines

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