Profile of oxidation in irradiated polyethylene

Yeom, Bong Yeol; Yu, Youlu; McKellop, Harry A.; Salovey, R.

doi:10.1002/(sici)1099-0518(19980130)36:2<329::aid-pola16>3.0.co;2-q

Cited by 70 publications

(36 citation statements)

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“…Upon gamma irradiation, following the formation of free radicals, chain scission as well as crosslinking occurs. [3][4][5][6][7][8][9][10] During shelf storage or in vivo, residual radicals react with oxygen diffusing from the surface, which generates peroxy radicals. The peroxy radicals continue to react over the period of years to lead to oxidative degradation.…”

Section: Introductionmentioning

confidence: 92%

“…The peroxy radicals continue to react over the period of years to lead to oxidative degradation. 3,4 While the crosslinking contributes to the enhancement of resistance to wear and creep, the oxidative chain scission deteriorates material properties. Hence, irradiation or post-irradiation heat treatment under an oxygenfree atmosphere is required.…”

Section: Introductionmentioning

confidence: 99%

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Mechanical properties of ultra-high molecular weight polyethylene irradiated with gamma rays

et al. 2004

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With the goal of enhancing the creep resistance of ultra-high molecular weight polyethylene (UHMWPE), we performed gamma irradiation and post-irradiation annealing at a low temperature, and investigated the crystalline structures and mechanical properties of the samples. Electron spin resonance spectra reveal that most of the residual radicals are stabilized by annealing at 100 °C for 72 h under vacuum. Both the melting temperature and crystallinity increase after increasing the dose and by post-irradiation annealing. When irradiated with the same dose, the quenched sample having a higher amorphous fraction exhibits a lower swell ratio than does the slow-cooled sample. The measured tensile properties correlate well to the crystalline structure of the irradiated and annealed samples. For enhancing creep resistance, high crystallinity appears to be more critical than a high degree of crosslinking.

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Section: Introductionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Mechanical properties of ultra-high molecular weight polyethylene irradiated with gamma rays

et al. 2004

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“…This initiation step turns the chain of the HTC into a free radical. In gamma irradiation processes, this initiation step is ensured by photons [41][42][43]. In this case, to understand how the scission of the C-C bond occurs, molecular reactions in the alkane must be described.…”

Section: Discussionmentioning

confidence: 99%

Modification of Hexatriacontane by O2–N2 Microwave Post-Discharges

Hody¹,

Belmonte²,

Pintassilgo

et al. 2006

Plasma Chem Plasma Process

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Etch rates of hexatriacontane (HTC) as high as ∼10 mg s −1 m −2 in late O 2 post-discharge are obtained at 333 K where no significant UV nor VUV irradiation occurs. Introducing N 2 in the gas mixture helps control the ratio of O/O 2 densities, which is shown to play a key role in the functionalization or etching of the HTC. The oxygen atoms are required for any further modification of the HTC because they initiate the formation of the radical chains by abstraction of one hydrogen. O( 3 P) atoms do not contribute directly to break the alkane chain close to room temperature but they can functionalise it. O 2 is the important reactive species for the etching because of the role played by the peroxide groups on the scission of the hydrocarbon chains.Keywords Cleaning · Post-discharge · Hexatriacontane PAC number 34.50-Dy Interactions of atoms, molecules, and their ions with surfaces photon and electron emission neutralization of ions

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“…[3] In this respect, higher energy radiation, such as gamma or electron beam, is widely used (up to 400 kGy). Yeom et al [4] reported that when polyethylene is irradiated by gamma rays in the presence of oxygen, free radicals, mostly alkyl radicals, are produced, which react with oxygen to yield ketones, probably due to b scission of peroxy or alkoxy radicals. This is Full Paper: The effect of gamma-irradiation on the structure, rheology, and mechanical properties of low density polyethylene (LDPE) films containing some new hindered amine stabilizers (HAS) has been investigated and the results obtained were compared to additive free samples.…”

Section: Introductionmentioning

confidence: 99%

“…In fact, a considerable amount of papers have been published, especially on differing polyethylene grades including recycled polymers, and the effect of gamma irradiation on both the structure and the physical properties has been revealed. [2][3][4][5][6][7][8] Taking into account the polymer oxidation process implying the free radical reaction with oxygen, questions have been raised as to whether hindered amine stabilizers (HAS) can be effective inhibitors of gamma induced oxidative degradation of low density polyethylene (LDPE) films. It is well established that HAS are excellent stabilizers for polyolefins against both UVand thermal oxidative degradation due to their multifunctional activities in the stabilization mechanisms (mainly scavenging alkyl and peroxy radicals).…”

Section: Introductionmentioning

confidence: 99%

Study of the Effects of Gamma Irradiation on the Structure and Physical Properties of Low Density Polyethylene Films Containing Hindered Amine Stabilizers

Kaci

Remili

Khima

et al. 2003

Macro Materials & Eng

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The effect of gamma‐irradiation on the structure, rheology, and mechanical properties of low density polyethylene (LDPE) films containing some new hindered amine stabilizers (HAS) has been investigated and the results obtained were compared to additive free samples. The HAS used involved various structures such as an alkoxyamine, a polymer bound HAS and a HAS modified with siloxane; these are commercially known as Tinuvin 123, Sanduvor PR 31 and Uvasil 299, respectively. It was found that the carbonyl index values measured by FTIR spectroscopy increased linearly with the radiation dose for all the samples studied, however this increase was less pronounced for the stabilized samples. The formation rates of carbonyls followed the order LDPE > LDPE/Uvasil 299 > LDPE/PR 31 > LDPE/Tinuvin 123. The second order derivative UV analysis showed the formation of vinyl groups in the irradiated samples at higher doses (812 kGy), while vinylidene groups were detected only in the films stabilized with PR 31 and Tinuvin 123. The curves of the melt flow rate (MFR) exhibited a fast increase for the unstabilized sample after 67 kGy, indicating the occurrence of chain scission. The stabilized samples on the other hand showed an evident increase in MFR from almost 300 kGy. The contribution of different HAS for the durability of LDPE films under γ rays was evaluated by determining the half‐value‐dose, which is related to the radiation resistance of the material. The results indicated that the presence of HAS in LDPE films improves the half‐value‐dose of those stabilized with Tinuvin 123 by 2.5 times against 2.4 and 2 for PR 31 and Uvasil 299, respectively. These data correlate well with the results obtained by FTIR and MFR measurements. Finally, the higher efficiency of Tinuvin 123 could be assigned to its appropriate oxidation state to enter the stabilization mechanism directly.An example of the new HAS.magnified imageAn example of the new HAS.

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Profile of oxidation in irradiated polyethylene

Cited by 70 publications

References 0 publications

Mechanical properties of ultra-high molecular weight polyethylene irradiated with gamma rays

Mechanical properties of ultra-high molecular weight polyethylene irradiated with gamma rays

Modification of Hexatriacontane by O2–N2 Microwave Post-Discharges

Study of the Effects of Gamma Irradiation on the Structure and Physical Properties of Low Density Polyethylene Films Containing Hindered Amine Stabilizers

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