Dissolution of Polyethylene Single Crystals in Xylene and Octadecane

Huseby, T. W.; Bair, H. E.

doi:10.1063/1.1655894

Cited by 27 publications

(13 citation statements)

References 11 publications

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“…The mass crystallinity ( w c ) of the polymer is determined according to the total enthalpy method:

w_{normalc} = \frac{Δ H_{normalf}}{w_{normalp} (normalΔ H_{f}^{0} - true \int_{T_{1}}^{T_{m}^{0}} (c_{p, a} - c_{p, c}) d T)}

where Δ H f is the measured melting enthalpy,

Δ H_{normalf}^{0}

is the melting enthalpy for 100% crystalline polyethylene (293 J g −1 ) at the equilibrium melting point, T 1 is an arbitrary temperature below the melting range,

T_{normalm}^{0}

is the equilibrium melting temperature (141.5 °C), w p is the mass fraction of polymer in the polymer/particle composite system, and c p,a and c p,c are, respectively, the specific heat capacities of the amorphous and crystalline components, which are obtained from Wunderlich and Baur . The crystal thickness ( L c ) associated with the melting peak temperature is calculated according to the Thomson–Gibbs equation:

L_{normalc} = \frac{2 σ_{normale}}{Δ H_{normalf}^{0} ρ_{normalc} (1 - \frac{T_{m}^{}}{T_{m}^{0}})}

where T m is the melting peak temperature, ρ c = 1003.0 kg m −3 and ρ a = 851.9 kg m −3 are the densities of, respectively, the crystalline and amorphous components, and σ e = 93 mJ m −2 is the fold surface free energy for linear polyethylene . Figure a shows the melting thermograms of pristine LDPE and HDPE together with those of their blends.…”

Section: Polyethylene Nanocomposites For High Voltage Insulationmentioning

confidence: 99%

The Role of Interfaces in Polyethylene/Metal‐Oxide Nanocomposites for Ultrahigh‐Voltage Insulating Materials

2017

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Recent progress in the development of polyethylene/metal-oxide nanocomposites for extruded high-voltage direct-current (HVDC) cables with ultrahigh electric insulation properties is presented. This is a promising technology with the potential of raising the upper voltage limit in today's underground/submarine cables, based on pristine polyethylene, to levels where the loss of energy during electric power transmission becomes low enough to ensure intercontinental electric power transmission. The development of HVDC insulating materials together with the impact of the interface between the particles and the polymer on the nanocomposites electric properties are shown. Important parameters from the atomic to the microlevel, such as interfacial chemistry, interfacial area, and degree of particle dispersion/aggregation, are discussed. This work is placed in perspective with important work by others, and suggested mechanisms for improved insulation using nanoparticles, such as increased charge trap density, adsorption of impurities/ions, and induced particle dipole moments are considered. The effects of the nanoparticles and of their interfacial structures on the mechanical properties and the implications of cavitation on the electric properties are also discussed. Although the main interest in improving the properties of insulating polymers has been on the use of nanoparticles, leading to nanodielectrics, it is pointed out here that larger microscopic hierarchical metal-oxide particles with high surface porosity also impart good insulation properties. The impact of the type of particle and its inherent properties (purity and conductivity) on the nanocomposite dielectric and insulating properties are also discussed based on data obtained by a newly developed technique to directly observe the charge distribution on a nanometer scale in the nanocomposite.

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“…The mass crystallinity ( w c ) of the polymer is determined according to the total enthalpy method:

w_{normalc} = \frac{Δ H_{normalf}}{w_{normalp} (normalΔ H_{f}^{0} - true \int_{T_{1}}^{T_{m}^{0}} (c_{p, a} - c_{p, c}) d T)}

where Δ H f is the measured melting enthalpy,

Δ H_{normalf}^{0}

is the melting enthalpy for 100% crystalline polyethylene (293 J g −1 ) at the equilibrium melting point, T 1 is an arbitrary temperature below the melting range,

T_{normalm}^{0}

L_{normalc} = \frac{2 σ_{normale}}{Δ H_{normalf}^{0} ρ_{normalc} (1 - \frac{T_{m}^{}}{T_{m}^{0}})}

Section: Polyethylene Nanocomposites For High Voltage Insulationmentioning

confidence: 99%

The Role of Interfaces in Polyethylene/Metal‐Oxide Nanocomposites for Ultrahigh‐Voltage Insulating Materials

2017

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“…However, these activation energies should have no influence on the equilibrium state in (57), (58) and (63), but only on the time of equilibrium approach. In consequence, the isothermal and lateral melting process of a lametla according to (74) does not cause a change of ASMi , i.e., zlsMi is independent of the extent of melting and of the degree of crystallinity a. As is to be seen from (57) the dependence of the equilibrium ratio__~N / N t on the temperature is rather insensitive so that ASMi remains nearly constant over the melting range as well ( fig.…”

Section: Iiii1mentioning

confidence: 84%

“…This fact could be confirmed by direct investigations of A. J. Kovacs et al [69] on polyethyleneoxid crystals. Consequently the melting behaviour at the lateral faces Q and Ob (47) in figure 5 is decisive for Aszk in (73) or ZlsMi in (74) and not the melting behaviour at the cover faces Oc. Only a few investigations of this behaviour from the molecular point of view have been carried out, for instance [59], but they, too, have been restricted to certain special cases.…”

Section: Iiii1mentioning

confidence: 95%

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Crystallization of low and high molecular materials

Kanig

1983

Colloid & Polymer Sci

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“…It is, therefore, impossible to correlate the results with structural data of the original crystals. BAIR et al [1][2][3] have contended t h a t radiation-induced crosslinking suppresses the lamellar thickening t o such an extent that the melting point, which is determined for a sample irradiated a t appropriate low doses, corresponds t o the actual melting of the original crystal without reorganization. This technique is based on an assumption that crosslinking occurring preferentially a t fold surfaces4-6) has nothing to do with the thermodynamic melting point of crystals.…”

Section: Zusammenfassungmentioning

confidence: 99%