Variations in unit cell dimensions in polyethylene

Walter, E. R.; Reding, F. P.

doi:10.1002/pol.1956.120219925

Cited by 132 publications

(34 citation statements)

References 6 publications

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“…46 Copolymers with longer branches formed a smectic structure, with only two broad characteristic diffraction peaks, 49 which has been reported separate grouping. The observed dilation of the unit cell was interpreted as a consequence of eiunder these rapid crystallization conditions, 17,49 was also found when thin films (10 mm) of sample ther partial branch inclusion 7,8,11,15,43 or of local stresses at the basal plane of the crystallite E were rapidly quenched. However, the samples studied in this work (of 0.3 mm thick) gave typical caused by the preferential accumulation of the excluded branches on the crystal surface.…”

Section: Resultsmentioning

confidence: 78%

“…polymer is crucially important to many structural Also well established is that there is a systematic studies, such as the determination of the crysdilation of the orthorhombic unit cell of random tallinity level from macroscopic density measureethylene copolymers and polyethylene containing ments and in the evaluation of x-ray scattering long-chain branches. [5][6][7][8][9][10][11][12][13][14][15] The lattice expands in intensities. These quantities are well established both the a and b direction in these cases with the for many polymers.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A study of the dilation of the unit cell of metallocene isotactic poly(propylenes): The monoclinic form

Isasi

Alamo

Mandelkern

1997

J. Polym. Sci. B Polym. Phys.

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The lattice parameters of a series of monoclinic metallocene poly(propylenes) of constant molecular weight are measured as a function of defect content, that vary between 0.3 and 2.35 total defects per 100 monomeric units. The parameters are also measured as a function of molecular weight for a fixed defect content and as a function of the crystallization temperature. The b axis is found to increase with decreasing isothermal crystallization temperature whereas only small changes are found for samples rapidly crystallized. The a and c axis showed basically no variation with crystallization temperature. The parameters of the unit cell were essentially constant with varying defect content in the poly(propylene) chain. Lack of observed effect on the dilation of the unit cell by increasing defects is a consequence of the rapid crystallization required to ensure formation of monoclinic crystals. The unit cell parameters increased as a mild function of the molecular weight. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2511–2521, 1997

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Section: Resultsmentioning

confidence: 78%

Section: Introductionmentioning

confidence: 99%

A study of the dilation of the unit cell of metallocene isotactic poly(propylenes): The monoclinic form

Isasi

Alamo

Mandelkern

1997

J. Polym. Sci. B Polym. Phys.

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“…8 The recent discovery of single center metallocene/alumoxane-based catalytic systems 18 has allowed the preparation of ethene-propene copolymers 19 -23 with quite narrow distribution of molecular mass and inter-and intramolecular distribution of chemical composition. Moreover, the availability of metallocenes endowed with dramatically different structures allows to control the product of reactivity ratios in the range from about 0.01 to more than 3, and the regioregularity (from only primary (1,2) insertions to up to 20% of secondary (2, 1) insertions) and stereoregularity (from substantially only m dyads to comparable amount of m and r dyads) of the propene sequences.…”

Section: Introductionmentioning

confidence: 99%

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] The larger part of these crystallinity studies has been devoted to copolymers useful for production of industrially relevant crosslinked elastomers, presenting ethene content generally lower than 85% by mol.…”

Section: Introductionmentioning

confidence: 99%

Pseudohexagonal crystallinity and thermal and tensile properties of ethene-propene copolymers

Guerra

Ballesteros

Venditto

et al. 1999

J. Polym. Sci. B Polym. Phys.

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Structural (X‐ray diffraction), melting (differential scanning calorimetry), as well as mechanical (tensile tests) characterizations on uncrosslinked ethene–propene copolymer samples, obtained using a metallocene‐based catalytic system and having an ethene content in the range 80–50% by mol, are reported. Samples with an ethene content in the range 80–60% by mol present a disordered pseudohexagonal crystalline phase, whose melting moves from ≈ 40°C down to ≈ −20°C as the ethene content is reduced. The dramatic influence of the crystalline phase on tensile properties of uncrosslinked ethene–propene copolymers is shown. In particular, highest elongation at break values are obtained for samples being essentially amorphous in the unstretched state and partially crystallizing under stretching. On the other hand, lowest tension set values (most elastic behavior) are observed for samples presenting, already in the unstretched state, microcrystalline domains acting as physical crosslinks in a prevailing amorphous phase. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1095–1103, 1999

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“…A similar isomorphism has been reported for poly(ethylene-copropylene). 15 The present copolymer is the first example of isomorphism of olefin copolymer containing a cyclic structure in the main chain.…”

Section: Resultsmentioning

confidence: 97%

Crystalline Structure of Polyethylene Containing 1,2- or 1,3-Disubstituted Cyclopentane Units in the Main Chain

et al. 2002

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Polyethylene having 1,2-or 1,3-disubstituted cyclopentane structures was prepared by copolymerization of ethylene and cyclopentene (CPE) or 1,5-hexadiene (HD), and the crystalline structure was studied. Treatment with fuming nitric acid preferentially degraded the amorphous phase of the copolymers, and the structure of degraded samples indicated that 1,3-disubstituted cyclopentane units were taken in the crystalline phase of poly(ethylene-co-HD). Infrared spectra of the copolymers indicated the increase of hexagonal-phase character in poly(ethylene-co-HD) with increasing content of 1,3-disubstituted cyclopentane units. Wide-angle X-ray diffraction patterns of poly(ethylene-co-HD) showed a continuous transition from the orthorhombic phase to the hexagonal phase in the copolymer with HD content less than 15 mol %. On the other hand, 1,2-disubstituted cyclopentane structures were not taken in the crystalline phase, but in the amorphous phase.

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Variations in unit cell dimensions in polyethylene

Cited by 132 publications

References 6 publications

A study of the dilation of the unit cell of metallocene isotactic poly(propylenes): The monoclinic form

A study of the dilation of the unit cell of metallocene isotactic poly(propylenes): The monoclinic form

Pseudohexagonal crystallinity and thermal and tensile properties of ethene-propene copolymers

Crystalline Structure of Polyethylene Containing 1,2- or 1,3-Disubstituted Cyclopentane Units in the Main Chain

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