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Digitale Medien

Fold surface of polyethylene single crystals as assessed by selective degradation studies. III. Application of the improved techniques to single crystals (1971)

Keller, A. ; Martuscelli, E. ; Priest, D. J. ; [weitere]

New York : Wiley-Blackwell

Journal of Polymer Science Part A-2: Polymer Physics 9 (1971), S. 1807-1837

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ISSN: 0449-2978

Schlagwort(e): Physics ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: Previous studies on selective degradation of polyethylene single crystals with fuming nitric acid have been extended, both by using acid of lower concentration which gave better control over the degradation, and by resorting to ozone as an oxidizing agent which among others enabled the degradation temperature to be conveniently lowered. The molecular weight distribution was followed by gel-permeation chromatography in the course of degradation. Complete consistency between these different methods has been established, modifying some of the previous conclusions reached by this method. The principal feature which emerges is that we have a distribution of fold lengths. The largest straight fold stems can stretch across nearly the entire layer defined by the low-angle x-ray period, while there is a continuous distribution of shorter folds terminating deeper down in the crystals. The limiting depth at which the number of terminating folds becomes negligible can be identified and quantitatively assessed. The method of analysis is described, and individual data are discussed in detail. This picture of a fold surface layer containing essentially adjacently reentrant folds of uneven length agrees with quite recent results on other related chain-folded systems (annealed crystals, short chains, bulk structures) obtained in these laboratories and thus appears to be of general validity. The consequences of the model for our picture on polymer crystals in particular on the nature of the “amorphous” component, are discussed.

Zusätzliches Material: 17 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pol.1971.160091006

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Digitale Medien

Crystallization of short aliphatic chains. II. Example of even fold surface with adjacent fold reentry and of a transition to chain extension (1972)

D'ilario, L. ; Keller, A. ; Martuscelli, E.

New York : Wiley-Blackwell

Journal of Polymer Science Part A-2: Polymer Physics 10 (1972), S. 239-252

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ISSN: 0449-2978

Schlagwort(e): Physics ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: As a continuation of the preceding study on the folding behavior of short polymer chains, an iodine-terminated paraffin having 156 Å peak molecular length and a sharp molecular weight distribution was prepared. The paraffin could be crystallized in lamellae of two different thicknesses: (A) thickness close to half the chain length (the most readily obtained); (B) thickness intermediate between half chain length and fully extended chain. Case A corresponds to each chain folding once with equal stems and with ends at the surface. Degradation behavior revealed that the folds must be of closely equal length giving rise to an even fold surface. In case B the situation is more involved: here the chain ends must turn into the lattice. Adjacent reentry is a necessity throughout. In both cases the lamellar thickness could be increased by annealing up to complete chain extension.

Zusätzliches Material: 9 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pol.1972.160100204

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Digitale Medien

Toughening of a highly cross-linked epoxy resin by reactive blending with bisphenol A polycarbonate. I. FTIR spectroscopy (1994)

Abbate, M. ; Martuscelli, E. ; Musto, P. ; [weitere]

Bognor Regis [u.a.] : Wiley-Blackwell

Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 395-408

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ISSN: 0887-6266

Schlagwort(e): epoxy resin ; polycarbonate ; FTIR spectroscopy ; polymer blend ; toughness ; Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: A highly cross-linked thermosetting epoxy resin was modified by a reactive blending process carried out in the presence of bisphenol A polycarbonate (PC). Prior to the curing process the PC component was dissolved at high temperature in the uncured epoxy matrix. FTIR investigation of this reactive mixture demonstrated the occurrence of physical and chemical interactions among the blend components. Isothermal kinetic measurements performed by FTIR spectroscopy showed that the presence of PC does not affect the overall curing mechanism but decreases both the initial reaction rate and the final conversion of reactants. © 1994 John Wiley & Sons, Inc.

Zusätzliches Material: 18 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/polb.1994.090320301

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Digitale Medien

Morphology and thermodynamic properties of solution-grown single crystals of trans-1,4-polybutadiene (1976)

Marchetti, A. ; Martuscelli, E.

New York : Wiley-Blackwell

Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 323-342

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ISSN: 0098-1273

Schlagwort(e): Physics ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: The morphology and thermal behavior of trans-1,4-polybutadiene single crystals prepared from dilute solutions in n-heptane have been investigated by electron microscopy, wide-angle and low-angle x-ray diffraction, and differential scanning calorimetry. The thickness of the single crystals of trans-1,4-PBD is much greater, for the same undercooling, than that of other linear polymers. From the calorimetric study, convincing evidence of the presence, in the single crystals, of crystalline blocks of form 1 with two different thermodynamic stabilities is obtained and the relative amounts are calculated. From thermodynamic considerations we find a value of 75°C for the equilibrium transition temperature between forms 1 and 2, 139°C for the equilibrium melting temperature of form 2, and 31.2 erg/cm2 for the fold-surface free energy of modification 2.

Zusätzliches Material: 16 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pol.1976.180140212

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An investigation on the chain-folding structure of an ethylene-propylene copolymer by selective degradation (1975)

Patel, G. N. ; Keller, A. ; Martuscelli, E.

New York : Wiley-Blackwell

Journal of Polymer Science: Polymer Physics Edition 13 (1975), S. 2281-2288

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ISSN: 0098-1273

Schlagwort(e): Physics ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: A renewed explanatory study is reported on the fold structure and branch location in single crystals of an ethylene-propylene copolymer by means of the ozone degradation method. By analogy with concurrent studies on linear polyethylenes a distribution of fold lengths is inferred, this distribution being broader, more uniform, and spreading deeper into the crystal interior in the case of the copolymer than for the linear polyethylene. Perhaps the most salient points of the work is that in contrast to nitric acid the oxidation by ozone does not obscure then characteristic CH3 infrared absorption band enabling the branch content to be followed during degradation. The single exploratory experiment of the present work reveals that while there is a certain amount of preference for the branches to accumulate near the fold surface, a substantial portion of them can still be located in the crystal interior. The potential of the present method for a more systematic study is indicated.

Zusätzliches Material: 4 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pol.1975.180131203

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Effect of chain defects on the morphology and thermal behavior of solution-grown single crystals of syndiotactic polypropylene (1974)

Marchetti, A. ; Martuscelli, E.

New York : Wiley-Blackwell

Journal of Polymer Science: Polymer Physics Edition 12 (1974), S. 1649-1666

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ISSN: 0098-1273

Schlagwort(e): Physics ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: The morphology of solution-grown single crystals of syndiotactic polypropylene with different degree of stereoregularity is compared. A sector formation phenomenon, found in some monolayer single crystals, is discussed in terms of possible crystallographic fold planes, growth planes, and gemination planes. A correlation between thermodynamic and morphological properties such as apparent enthalpy of fusion, critical long spacing, critical annealing temperature, and the number of configurational chain defects along the macromolecule has been found. Two endothermic peaks are observed in the DSC thermograms of single-crystal aggregates of syndiotactic polypropylene. The low-temperature peak is attributed to melting of crystals or parts of crystals with incorporated chain defects. The high-temperature peak corresponds to the melting endotherm of more regular crystalline zones. The peak-area ratio seems to depend on the degree of stereoregularity.

Zusätzliches Material: 14 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pol.1974.180120812

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Polypropylene spherulite morphology and growth rate changes in blends with low-density polyethylene (1984)

Galeski, A. ; Pracella, M. ; Martuscelli, E.

New York : Wiley-Blackwell

Journal of Polymer Science: Polymer Physics Edition 22 (1984), S. 739-747

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ISSN: 0098-1273

Schlagwort(e): Physics ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: Morphological studies of isotactic polypropylene/low-density polyethlene blends revealed that the shape, size, and orientation of LDPE occlusions remain undisturbed during the crystallization of IPP spherulites. On the other hand, LDPE occlusions introduce large changes in the internal structure of IPP spherulites. It was found that many new boundaries similar to those between spherulites are fromed when the crystallizing front passes the LDPE occlusion. Dead-ended boundaries with soft LDPE occlusions at the ends give rise to an improvement of the impact properties. It was shown that LDPE obstacles do not influence significantly the IPP spherulite growth rate in thin films or in the bulk.

Zusätzliches Material: 11 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pol.1984.180220415

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