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Arnal, María L.; Balsamo, Vittoria; Ronca, G.; Sánchez, A.; Müller, Alejandro J.; Cañizales, Edgar; Navarro, Caribay Urbina de

doi:10.1023/a:1010137408023

Cited by 128 publications

(110 citation statements)

References 27 publications

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“…A series of relatively sharp peaks can be seen, indicating that the thermal fractionation process was successful in separating a fraction for each step where annealing was present. [13] According to the experimental protocol of the SSA technique applied to NXLPE, a total of ten different T s temperatures were used. The first T s temperature of 108 8C is a temperature that only causes pure self-nucleation in the polymer.…”

Section: Resultsmentioning

confidence: 99%

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Application of the SSA Calorimetric Technique to Characterise an XLPE Insulator Aged under Multiple Stresses

Paolini

Ronca

Feijoo

et al. 2001

Macromol. Chem. Phys.

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In this work the thermal behaviour of crosslinked low density polyethylene (XLPE) used as an insulator for commercial underground high tension (15 kV) cables was studied. Three types of materials were selected: an uncrosslinked low density polyethylene (NXLPE) used as a control sample, an XLPE and an aged XLPE sample. The ageing conditions involved the application of multiple stresses: temperature, voltage and voltage impulses during 60 d under time and temperature cycles that are the most representative load of daily operation in Caracas, Venezuela. The effect of morphology segregation or thermal fractionation under multiple stresses conditions was analysed by measuring the percentage of crosslinking before and after the ageing tests were performed, and by investigating the thermal response of the material by conventional DSC and by the application of the successive self‐nucleation and annealing (SSA) thermal fractionation technique. The degree of crosslinking was found to vary in the material depending on the distance from the conductor because a thermal gradient is generated radially during the curing reaction. Such differences did not significantly affect the usual DSC heating scans of the samples. However, when SSA was applied, a difference in the distribution of thermal fractions was detected as a function of the distance towards the conductor that could be correlated to the variations in the crosslinking degree. After the accelerated ageing the thermal response of XLPE changes as evidenced by the presence of multiple melting peaks in subsequent DSC heating scans. This multiple melting was interpreted, as a first approximation, as arising from thermal fractionation during ageing (ignoring the possible effects of the other stresses applied) and SSA was able to simulate a similar fractionation that was very accurate in the prediction of the exact temperatures of the melting peaks produced.

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Section: Resultsmentioning

confidence: 99%

“…Therefore, we decided to apply besides conventional DSC (differential scanning calorimetry) our recently developed DSC based technique, [12,13] the successive selfnucleation and annealing (SSA) to characterise our laboratory aged underground transmission cables.…”

Section: Introductionmentioning

confidence: 99%

Application of the SSA Calorimetric Technique to Characterise an XLPE Insulator Aged under Multiple Stresses

Paolini

Ronca

Feijoo

et al. 2001

Macromol. Chem. Phys.

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“…The most important parameters for the SSA method are the first T s value to be used, the temperature interval between T s values, the residence time at T s , and the heating rates during the thermal conditioning steps. 36 A spacing of 3 8C instead of 6 8C probably gave a slightly better separation and more peaks, but increases in the measuring time were enormous. An increase in the holding time did not promote a higher number of signals, but more perfect crystals were expected at higher time consumption.…”

Section: Dsc Analysismentioning

confidence: 99%

Thermal and mechanical analysis of metallocene‐catalyzed ethene–α‐olefin copolymers: The influence of the length and number of the crystallizing side chains

Piel

Starck

Seppälä

et al. 2006

J. Polym. Sci. A Polym. Chem.

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Copolymers of ethene and 1-octene, 1-dodecene, 1-octadecene, and 1-hexacosene were carried out with [Ph 2 C(2,7-ditert BuFlu)(Cp)]ZrCl 2 /methylalumoxane as a catalyst to obtain short-chain branched polyethylenes with branch lengths of 6-26 carbon atoms. This catalyst provided high activity and a very good comonomer and hydrogen response. In this study, the influence of the length and number of the side chains on the mechanical properties of the materials was investigated. The crystalline methylene sequence lengths of the copolymers and lamellar thicknesses were calculated after the application of a differential scanning calorimetry/successive self-annealing separation technique. By dynamic mechanical analysis, the storage modulus as an indicator of the stiffness and the loss modulus as a measure of the effect of branching on the a and b relaxations were studied. The results were related to the measurements of the polymer density and tensile strength to determine the effect of longer side chains on the material properties. The hexacosene copolymers had side chains of 24 carbons and remarkable material properties very different from those of conventional linear low-density polyethylenes. The side chains of these copolymers crystallized with one another and not only parallel to the backbone lamellar layer, depending on the hexacosene concentration in the copolymer. The side chains crystallized even at low hexacosene concentrations in the copolymer. A transfer of these results to 16 carbons

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“…The method involves applying a thermal treatment that includes intercalated isothermal steps, which promote the nucleation and annealing of crystals. A final standard heating scan reveals the succession of endothermic signals corresponding to the melting of each crystalline entity [15]. Müller et al [14] analyzed the branching distribution from linear low-density polyethylene (LLDPE), pointing out that the melting enthalpy of each signal can be considered proportional to the normalized weight fraction of molecular populations with a certain branching content.…”

Section: Introductionmentioning

confidence: 99%

Influence of processing on the ethylene-vinyl alcohol (EVOH) properties: Application of the successive self-nucleation and annealing (SSA) technique

Urquiza¹,

Santana

Gámez‐Pérez³

et al. 2010

Express Polym. Lett.

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Abstract. Films of EVOH copolymers, processed three times by twin-screw extrusion were prepared using a cast-film line. The variation on the melt flow rate (MFR) and rheological behaviour of the films were determined, as well as the thermal properties assessed by differential scanning calorimetry (DSC) and dynamic-mechanical thermal analysis (DMTA). As the results showed that the reprocessing induced an increase in the viscosity and orientation of the films, it was suggested that structural modifications from chain-extension or cross-linking reactions promoted by hydroxyl and residual acetoxyl groups, could be occurring. The successive self-nucleation and annealing (SSA) technique was applied, evidencing the structural modifications on the EVOH copolymer.

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Cited by 128 publications

References 27 publications

Application of the SSA Calorimetric Technique to Characterise an XLPE Insulator Aged under Multiple Stresses

Application of the SSA Calorimetric Technique to Characterise an XLPE Insulator Aged under Multiple Stresses

Thermal and mechanical analysis of metallocene‐catalyzed ethene–α‐olefin copolymers: The influence of the length and number of the crystallizing side chains

Influence of processing on the ethylene-vinyl alcohol (EVOH) properties: Application of the successive self-nucleation and annealing (SSA) technique

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