The influence of molecular orientation on the crosslinking/oxidative behaviour of iPP exposed to gamma radiation

Suljovrujić, E.

doi:10.1016/j.eurpolymj.2009.03.017

Cited by 23 publications

(15 citation statements)

References 83 publications

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“…In many studies, the increase in crystallinity has been attributed to lamellar thickening and/or the increase in crystal perfection or to the formation of new lamellae by chemicrystallization of small fractions produced by chain scission during irradiation [61,62]. On the other hand, the decrease in crystallinity was attributed to the formation of cross-linking [63] and to the radiation-induced defects within the crystals, as well as to those at the lateral grain boundaries [26,32]. The decrease in crystallinity is concomitant with the increase in the gel content observed in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The quantification of the various oxidation products of PP (as a result of gamma, photo, and thermal oxidation) was done by Lacoste et al [57,58]. The radiation-induced modifications that occur in the hydroxyl and carbonyl region were investigated in our previous papers [6,21,32], too. The major oxidation products in irradiated iPP are the tertiary hydroperoxides, which are unstable and undergo radical decomposition to other more stable oxidative products with an increase in radiation dose and their concentration.…”

Section: Resultsmentioning

confidence: 99%

“…Thus, exposition to radiation can be used to increase the dielectric activity and to investigate low-visible dielectric relaxations in apolar polyolefins [19,25]. Even though the overall radiation chemistry of PP was investigated in detail and several comprehensive reviews are available on this topic [26][27][28][29][30][31], the effects of radiation on dielectric relaxation behaviour have not been investigated to an appreciable extent [6,19,21,[32][33][34]. A major application of high-energy radiation is cross-linking of insulation; cross-linking to a gel content of 55% was shown to be beneficial for cable insulation [26].…”

Section: Introductionmentioning

confidence: 99%

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Complete relaxation map of polypropylene: radiation-induced modification as dielectric probe

Suljovrujić

2012

Polym. Bull.

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The molecular relaxation behaviour of isotactic polypropylene (iPP) exposed to gamma radiation in air to various absorbed doses (up to 700 kGy) has been investigated by dielectric loss (tan d) analysis; the polar (mainly carbonyl and hydroperoxide) groups that were introduced by radiation-induced oxidation were considered as tracer groups. All relaxation zones (a, b, c and d in the order of decreasing temperature), between 25 K and melting temperature, were studied in the frequency range from 1 kHz to 1 MHz. The changes observed in the dielectric relaxation spectra were related to the modifications in the structural and morphological parameters attributed to exposure of the iPP samples to radiation. Wide-angle X-ray diffraction was used to investigate radiation-induced changes in the crystalline structure and degree of crystallinity, since the a relaxation is connected with this phase. Infrared spectroscopy and gel measurements were used to determine the changes in the oxidative degradation and the degree of network formation, respectively. Conclusions derived using different methods were compared. This study reveals high dielectric and/or relaxation sensitivity of iPP to gamma radiation. Disappearance of the lowtemperature dielectric (c and d) relaxations together with large changes in intensity, position and activation energy of the dielectric a relaxation are observed with gamma irradiation and are mainly connected with oxidative degradation in iPP structure.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Complete relaxation map of polypropylene: radiation-induced modification as dielectric probe

Suljovrujić

2012

Polym. Bull.

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“…Another author has made this kind of experiment at 100°C [25]. The chain entanglement in the interlamellar amorphous region plays an important role in the deformation-induced structure changes during uniaxial stretching.…”

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confidence: 98%

“…The excellent resolution of AFM to describe surface topography has opened new opportunities to study surface deformation in polymeric materials [18][19][20][21]. Many authors have investigated the structure and morphological properties of stretched PP films [22,23] and the influence of molecular orientation on the crosslinking behavior iPP, exposed to gamma radiation [24,25].…”

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confidence: 99%

Morphological characterization of branched PP under stretching

et al. 2012

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An effective approach to achieve high-melt strength polymer is to add long chain branches onto backbone species using gamma radiation. Grafting and branching result from macroradicals combinations during the irradiation process. Polypropylene films were prepared starting with irradiation process of the pellets with a 60 Co source at doses of 5, 12.5, and 20 kGy under acetylene to improve melt strength and drawability. After irradiation, polypropylene films were obtained by compression molding, at 190°C and pressure of 80 bar, and dive into a water tank at 23°C, which generally favors the formation of an amorphous phase. The thin films were stretched at 170°C using a universal testing machine. Film surface morphology and the thermal properties, were analyzed, using atomic force microscopy, scanning electron microscopy and differential scanning calorimetry. We had a different molecular structure that requested the study of their micro and nanostructure. The results showed some evidence of fibrillar structures containing crystallites and gel formation. Fibrils oriented along the stretching direction were observed.

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Effects of Accelerated Thermal Aging on Polypropylene Modified by Irradiation Process

Oliani¹,

Fermino²,

Lima³

et al. 2015

Characterization of Minerals, Metals, and Materials 2015

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The influence of molecular orientation on the crosslinking/oxidative behaviour of iPP exposed to gamma radiation

Cited by 23 publications

References 83 publications

Complete relaxation map of polypropylene: radiation-induced modification as dielectric probe

Complete relaxation map of polypropylene: radiation-induced modification as dielectric probe

Morphological characterization of branched PP under stretching

Effects of Accelerated Thermal Aging on Polypropylene Modified by Irradiation Process

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