Photo-oxidation of thick polymer samples—Part II: The influence of oxygen diffusion on the natural and artificial weathering of polyolefins

Cûnliffe, A.V.; Davis, A.

doi:10.1016/0141-3910(82)90003-9

Cited by 160 publications

(54 citation statements)

References 14 publications

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“…Equation (2), the expression for the oxygen consumption rate, has been combined with standard diffusion expressions [27] to model diffusion-limited oxidation (DLO) effects for samples with planar geometry [3]. The resulting theoretical expressions have been shown to give quantitative agreement with experimental results for both thermoxidative aging of nitrile and neoprene rubbers [5] and radiation-oxidative aging of EPDM [4] and viton [28] materials.…”

supporting

confidence: 50%

“…For commercially formulated polymers, many potential problems can lead to non-Arrhenius behavior [1]. Some of these are dependent on physical effects such as 1) changes in chemistry caused by taking data or extrapolating across a polymer transition [2], 2) difision-limited oxidation [3][4][5] and 3) complex antioxidant behavior involving its redistribution by internal diffision and evaporation/blooming at the sample surface [6][7]. Others are chemically based and result in changes in the effective activation energy brought about by such things as a switch in the dominant mechanism as the temperature is changed or a slow temperature-dependent change due to the complex form of the effective activation energy [1].…”

Section: Introductionmentioning

confidence: 99%

“…The parameter a' is used hereto distinguish the disk theory from the theory for sheet material of thickness L that utilizes the parameter CZ, given by [3] ClL2 .-D…”

mentioning

confidence: 99%

“…The resulting theoretical expressions have been shown to give quantitative agreement with experimental results for both thermoxidative aging of nitrile and neoprene rubbers [5] and radiation-oxidative aging of EPDM [4] and viton [28] materials. For the current work, a solution analogous to that derived for planar geometry [3], but relevant to a cylindrical specimen, was necessary [24]. The CSR sample was modeled as a cylindrical disk having unit thickness and radius a.…”

mentioning

confidence: 99%

“…Modeling DLO effects involves the coupling of diffimion equations with kinetic expressions for the oxygen consumption rate [1,[3][4][5]24]. A particularly useful and general kinetic rate expression is based on a variant of the basic autoxidation scheme (BAS), which has been utilized for more than 50 years [25,26] to describe the oxidation of organic materials.…”

mentioning

confidence: 99%

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Methods for Predicting More Confident Lifetimes of Seals in Air Environments

Gillen

Celina

Keenan

2000

Rubber Chemistry and Technology

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We have been working for many years to develop improved methods for predicting the lifetimes of polymers exposed to air environments and have recently turned our attention to seal materials. This paper describes an extensive study on a butyl material using elevated temperature compression stress-relaxation (CSR) techniques in combination with conventional oven aging exposures. The results initially indicated important synergistic effects when mechanical strain is combined with oven aging, as well as complex, non-Arrhenius behavior of the CSR results. By combining modeling and experiments, we show that diffusion-limited oxidation (DLO) anomalies dominate traditional CSR experiments. A new CSR approach allows us to eliminate DLO effects and recover Arrhenius behavior. Furthermore, the resulting CSR activation energy (EJ from 125°C to 70"C is identical to the activation energies for the tensile elongation and for the oxygen consumption rate of unstrained material over similar temperature ranges. This strongly suggests that the same underlying oxidation reactions determine both the unstrained and strained degradation rates. We therefore utilize our ultrasensitive oxygen consumption rate approach down to 23°C to show that the CSR E~likely remains unchanged when extrapolated below 70°C, allowing very confident room temperature lifetime predictions for the butyl seal.

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supporting

confidence: 50%

Section: Introductionmentioning

confidence: 99%

“…The parameter a' is used hereto distinguish the disk theory from the theory for sheet material of thickness L that utilizes the parameter CZ, given by [3] ClL2 .-D…”

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Methods for Predicting More Confident Lifetimes of Seals in Air Environments

Gillen

Celina

Keenan

2000

Rubber Chemistry and Technology

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Role of oxygen in biodegradation of poly(etherurethane urea) elastomers

Schubert

Wiggins

Anderson

et al. 1997

J. Biomed. Mater. Res.

106

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It is generally accepted that biodegradation of poly(etheruethane urea) (PEUU) involves oxidation of the polyether segments on the surface where leukocytes are adhered. The influence of dissolved oxygen, which is known to control oxidation of polymers in more traditional environments, was explored in this study. Specimens treated in vitro with hydrogen peroxide-cobalt chloride for 12 days exhibited a brittle, degraded surface layer about 10 microm thick. Attenuated total reflectance-Fourier transform infrared spectroscopy of the surface revealed that the ether absorbance at 1110 cm(-1) gradually decreased with in vitro treatment time to 30% of its initial value after 12 days. In contrast, 6 days in vitro followed by 6 days in air produced a decrease to 12% of the initial volume. Therefore, removing a specimen from the in vitro solution after 6 days and exposing it to air for the remainder of the 12 days actually resulted in more oxidation than leaving it in the in vitro solution for the entire 12 days. These results suggest that PEUU degrades by an autooxidation mechanism sustained by oxygen. By successfully modeling the depth of the surface degraded layer with a diffusion-reaction model, it was demonstrated that PEUU biodegradation is controlled by diffusion of oxygen into the polymer.

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Subsurface oxidation of polyethylene

Daly

Yin

1998

J. Biomed. Mater. Res.

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Since the 1960s ultrahigh molecular weight polyethylene has been a primary bearing material in orthopedic prostheses. Most polyethylene components have been sterilized by exposure to gamma radiation, but in the presence of oxygen this promotes degradation and correlates with component failure in the body. To better understand the mechanism of degradation, we measured oxidation profiles for components shelf aged 5.8 and 10.9 years. Microtomed sections from each component were analyzed for ketones, which are the primary oxidation products, by FTIR spectroscopy. Maximum ketone concentrations in both cases were found several millimeters below the surface. We propose a model to explain the profiles. Alkyl radicals, which are uniformly generated in the polyethylene during irradiation, react with peroxyl radicals, which are produced by alkyl radicals with oxygen to form ketones. At the component surface ketone levels are low because high oxygen concentrations deplete alkyl radicals, creating an excess of peroxyl radicals. In the bulk material ketones are low because low oxygen concentrations limit the formation of peroxyl radicals. However, just below the surface the concentrations of alkyl and peroxyl radicals balance, promoting ketone production. A computer simulation that accounts for the coupling of these reactions with the diffusion of oxygen shows a good agreement with the measured profiles.

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Photo-oxidation of thick polymer samples—Part II: The influence of oxygen diffusion on the natural and artificial weathering of polyolefins

Cited by 160 publications

References 14 publications

Methods for Predicting More Confident Lifetimes of Seals in Air Environments

Methods for Predicting More Confident Lifetimes of Seals in Air Environments

Role of oxygen in biodegradation of poly(etherurethane urea) elastomers

Subsurface oxidation of polyethylene

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