Crystallinity in chemically crosslinked low density polyethylenes: 2. Crystallization kinetics

Phillips, Peter; Kao, Y.H.

doi:10.1016/0032-3861(86)90261-2

Cited by 72 publications

(22 citation statements)

References 18 publications

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“…Hence, the crystallization process of the gel fraction requires higher degrees of supercooling than that for the whole irradiated PVDF, when both are cooled from the melt at a constant rate. This is in agreement with previous studies on the effect of crosslink density on the crystallization of polymers, [15][16][17][18][19] which all concluded that crosslinking reduces the rate of crystallization in crosslinked melts. Moreover, considerable differences were reportedg in the crystallization of extracted and unextracted chemically crosslinked polyethylene.…”

Section: Results a N D Discussionsupporting

confidence: 93%

The sol/gel contribution to the behavior of γ‐irradiated poly(vinylidene fluoride)

Rosenberg

Siegmann

Narkis

et al. 1991

J of Applied Polymer Sci

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SYNOPSISPoly (vinylidene fluoride) films were y-irradiated in the dose range of 1-20 Mrad, resulting in up to 74% gel. The irradiated polymer undergoes both crosslinking and chain scission, about 5 : 3 events, respectively. Swelling measurements indicate an increasing crosslink density with the gel content, already at the lower doses. Thermal analysis of the gel fraction and the unextracted irradiated samples shows that although crosslinking affects the crystallization, degree of crystallinity, and the melting characteristics, the behavior of the crosslinked material is predominantly controlled by the extractable sol fraction which consists of the more mobile original chains, branched chains, and degraded ones. The crosslinks, already at low density, retard the development of ordinary crystalline polymer morphology.

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Section: Results a N D Discussionsupporting

confidence: 93%

The sol/gel contribution to the behavior of γ‐irradiated poly(vinylidene fluoride)

Rosenberg

Siegmann

Narkis

et al. 1991

J of Applied Polymer Sci

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“…The branching or crosslinking unit considerably increased the nucleation density of PP and accelerated the crystallization. 20 When the AO was added, T c lay between that of the linear PP and the sonicated PP without the AO.…”

Section: Rheological Propertiesmentioning

confidence: 99%

Rheological properties of polypropylene modified by high‐intensity ultrasonic waves

Kim

Nam²,

Lee³

et al. 2005

J of Applied Polymer Sci

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ABSTRACT:A new method using high-intensity ultrasonic waves, instead of peroxide-aided reactive extrusion, was applied to modify a linear polypropylene into a branched structure. The ultrasonic waves induced chain scission and created reactive macromolecules of polypropylene successfully in the melt state without any peroxide. To enhance and control the recombination reaction during sonication, a multifunctional agent and an antioxidant were used. The rheological property measurements clearly confirmed that the modified polypropylene had a nonlinear branched structure. It showed shear-thinning behaviors in its viscosities at low frequencies, high elastic behaviors in Cole-Cole plots, and a high rheological polydispersity index in comparison with a linear polypropylene. The degradation or recombination of polypropylene was adequately controlled by an antioxidant, which stabilized the structure during sonication. Also, the use of an antioxidant was quite effective in improving the extrusion processability by delaying the instability of the extrudate to a higher shear rate.

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“…Percent extractables (sol fraction), crosslink density, crystallinity, and other characteristic parameters were obtained using techniques already described in detail elsewhere (2,6).…”

Section: Methodsmentioning

confidence: 99%

“…Since the introduction of extruded polyethylenic insulation almost twenty years ago problems of dielectric breakdown associated with thermal or thermoelectric aging have surfaced. Recently a thorough study of the crystallization and morphology of crosslinked polyethylenes was conducted (1)(2)(3)(4). A s part of a study of the complex annealing behavior of these materials (5) a large sharp melting peak at 110 to 112°C was observed for annealing near and above the return-to-the baseline melting point.…”

Section: Introductionmentioning

confidence: 99%

Melt immiscibility in crosslinked polyethylene

Phillips

Vatansever

1990

Polymer Engineering & Sci

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Low density polyethylene crosslinked by decomposition of dicumyl peroxide shows evidence for two phases being present in the melt in a narrow temperature range just above the melting point. The effect has been studied in detail using differential scanning calorimetry, transmitted light intensity, and wide angle X‐ray diffraction studies at 107°C. It is believed that the effect is caused by the presence of relatively low molecular weight molecules which remain as an extractable fraction after crosslinking.

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Crystallinity in chemically crosslinked low density polyethylenes: 2. Crystallization kinetics

Cited by 72 publications

References 18 publications

The sol/gel contribution to the behavior of γ‐irradiated poly(vinylidene fluoride)

The sol/gel contribution to the behavior of γ‐irradiated poly(vinylidene fluoride)

Rheological properties of polypropylene modified by high‐intensity ultrasonic waves

Melt immiscibility in crosslinked polyethylene

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