Dynamic mechanical relaxations in annealed and irradiated polyethylenes

Juano-Arbona, V. Sáenz de; Ribes‐Greus, A.; Calleja, R. Dı́az; Alcaina–Miranda, M.I.; Hierro-Navarro, Pilar Del; Sanz-Box, Concepcíon; Trijueque-Monge, José

doi:10.1016/0022-3093(94)90625-4

Cited by 10 publications

(5 citation statements)

References 8 publications

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“…As sample C is the one that exhibits this effect more significantly, it has been calculated the apparent activation energy of its β relaxation for 15 and 21 months of exposure, when the peak is more prominent (Table IV). Estimated values of about 60 kcal/mol has been found, similar to the ones obtained by these authors for high‐density polyethylenes irradiated at low doses (2 and 20 Mrad) 18…”

Section: Resultssupporting

confidence: 88%

Viscoelastic behavior of degradable polyolefins aged in soil

Contat‐Rodrigo

Ribes‐Greus

2000

J. Appl. Polym. Sci.

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Samples of polypropylene and a high density polyethylene/polypropylene blend filled with different biodegradable additives (rice starch/iron oxide mixture, Bioefect 72000 and Mater‐Bi AF05H) have been subjected to an outdoor soil burial test for 21 months. Changes on the morphology of the samples have been studied by differential scanning calorimetry. The degradation process also has been analyzed in terms of the mechanical behavior of the polymers. The three characteristic relaxation zones α, β, and γ (in order of decreasing temperature) of the dynamic‐mechanical relaxation spectra of the samples have been characterized according to the Fuoss–Kirkwood equation. When two relaxations were overlapped, a deconvolution method was applied. It has been observed that the degradation process affects just to a small extent the amorphous phase of the polymers. That the β relaxation is the most sensitive to the exposure time suggests that degradation starts in the crystalline–amorphous interface. However, the crystalline phase is also affected significantly by the degradation process. The mechanical results are in good agreement with the calorimetric measurements, proving that degradation takes place in two stages with different time scales depending on the additive used. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1707–1720, 2000

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Section: Resultssupporting

confidence: 88%

Viscoelastic behavior of degradable polyolefins aged in soil

Contat‐Rodrigo

Ribes‐Greus

2000

J. Appl. Polym. Sci.

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“…The discussion is widened because of the possible presence of many processes in this relaxation and because of their localization. Many studies indicate that the mechanical and dielectric g relaxation zone contains two or even more relaxations of different origins, and with different relaxation times and activation energies (Alberola et al, 1992a(Alberola et al, , 1992bAshcraft and Boyd, 1976;Laredo et al, 1999;Ribes-Greus and Diaz-Calleja, 1989; Sa!enz de Juano-Arbona et al, 1994, 2002. According to Stehling and Mandelkern, (1970) and Alberola et al, 1992aAlberola et al, , 1992b, the g relaxation is related to the glass transition, and for others, this relaxation can be regarded as a sub-glass transition attributed to the local motion of the central C-C bond of short chain segments (by crank-shaft Perepechko, 1981 or flip-flop mechanism Boyd and Breitling, 1974) and/or local motion of loose chain ends in the amorphous phase (Matsuo et al, 2003).…”

Section: Crystallinity (%)mentioning

confidence: 99%

Dielectric study of post-irradiation effects in gamma-irradiated polyethylenes

Suljovrujić

2010

Radiation Physics and Chemistry

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“…Over the years, the effects of high‐energy radiation on polyethylene have been extensively studied,2–20 but they are still subject to debate because of the variety of interpretations proposed by different authors. Irradiation causes important changes that often occur simultaneously, that is, crosslinking processes at chain ends, unsaturations, and main chain scissions, for example, and consequently changes on the melting behavior and crystallinity.…”

Section: Introductionmentioning

confidence: 99%

“…The purpose of this work was to study the effect of different doses of ionizing radiation from a γ‐source on the melting behavior of high‐ and low‐density polyethylenes by means of differential scanning calorimetry (DSC). This technique has been proposed by many authors6–11, 14–16, 20 as a suitable analytical tool for these studies when the measurement is performed at high enough heating rates (10–20°C/min) given that at such heating rates reorganization effects during the scan are minimal.…”

Section: Introductionmentioning

confidence: 99%

Differential scanning calorimetry studies on high‐ and low‐density annealed and irradiated polyethylenes: Influence of aging

Vallés-Lluch¹,

Contat‐Rodrigo²,

Ribes‐Greus³

2003

J of Applied Polymer Sci

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ABSTRACT:The effect of ␥-radiation, followed by 10 years storage at ambient conditions, on the thermal behavior of different types of high-and low-density commercial polyethylenes was studied. First, samples were annealed to improve the crystalline content. Next, they were irradiated, after which fusion endotherms, melting temperatures, crystallinity indices, and lamellar thicknesses were obtained by differential scanning calorimetry (DSC). The change in the thermal parameters for the first and second meltings were related to the absorbed doses. Afterward, the samples were stored at ambient conditions for 10 years and then scanned again by DSC to assess the influence of aging on previously irradiated samples. The results showed that the changes on the morphological structure undergone by the samples with the storage time were highly dependent on the polyethylene type and the absorbed radiation dose. The high-density polyethylene was the most sensitive to radiation and storage, whereas the low-density polyethylene with the lowest molecular weight and the highest degree of branching was the least affected. In general, the changes observed during irradiation can be explained in terms of an increase of imperfections and chain scissions. The storage can be understood as a slow crystallization process at low radiation doses, and as a decrease of the crystalline structure at high doses.

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Dynamic mechanical relaxations in annealed and irradiated polyethylenes

Cited by 10 publications

References 8 publications

Viscoelastic behavior of degradable polyolefins aged in soil

Viscoelastic behavior of degradable polyolefins aged in soil

Dielectric study of post-irradiation effects in gamma-irradiated polyethylenes

Differential scanning calorimetry studies on high‐ and low‐density annealed and irradiated polyethylenes: Influence of aging

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