radiation-induced oxidation, cross- linking, and grafting ...€¦ · longer radical lifetime is...
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Radiation-induced Oxidation, Cross-linking, and Grafting of UHMWPE
Guozhong Wu
[email protected] Institute of Applied Physics, Chinese Academy of Sciences, China
ICARSTApril 25-28, 2017
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What is UHMWPE?UHMWPE (ultra–high molecular weight polyethylene) has an average molecular weight larger of >1.5×106, with high chemical resistance, excellent biocompatibility, mechanical properties and is widely used in medical devices, engineering and defense supplies.
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Low surface energy and poor compatibility, Li et al. CST. 2015
Some drawbacks of UHMWPE
These drawbacks may be overcome by radiation technology.
P o o r t h e r m a l a n d c re e p re s i s tance , Kromm e t a l . polymer testing. 2003
wear resistance should be improved, Silvia et al. wear. 2014
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Stable radical formation in UHMWPE fiber after irradiation
3320 3360 3400 3440 3480 Magnetic Field(Gauss)
in vacuum
1
2
3
4
3320 3360 3400 3440 3480
1 (x 2)
2 (x 2)
3 (x 2)
4 (x 2)in air
ESR spectra of the UHMWPE fiber irradiated in vacuum and in air at room temperature with a dose rate of 0.73 Gy/s. 1: 10 kGy, 2: 60 kGy, 3: 130 kGy, 4: 200 kGy. (×2) indicates the magnification of spectrum by a factor of two.
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Long lifetime of free radials in UHMWPE powder and fiber
Half-life: 26 days Half-life: 13 days
UHMWPE fiber
UHMWPE
Longer radical lifetime is easy for grafting polymerization.
UHMWPE
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Radiation oxidation of UHMWPE powder in air
For UHMWPE irradiated in air, the oxidation can’t be avoided.
C=O C=O
FT-IR curves UHMWPE powder irradiated by (a) gamma ray and (b) e-beams in air.
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The oxidation level is dependent on the dose and the low dose rate. γ ray irradiation induced more oxidation than e-beam irradiation.
powder irradiated in air fiber
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powder 300 kGy fiber 180 kGy
A large specific surface area leads to serious oxidation.
Potential application: additive in nylon
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Static contact angle of UHMWPE powder after gamma ray and e-beams irradiation.
Radiation oxidation enhanced surface wettability of UHMWPE.
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Radiation cross-linking of UHMWPE sheet
Gel content of UHMWPE sheet irradiated by gamma rays in air and with post-annealing.
For UHMWPE sheet irradiated in air, cross-linking is the dominant reaction during irradiation.
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Radiation cross-linking improves the creep-resistance of UHMWPE sheet.
Creep elongation of UHMWPE sheet after gamma ray irradiation in air.
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Highly cross-linked UHMWPE sheet shows good creep-resistance.
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R a d i a t i o n c r o s s - l i n k i n g increases Young’s modulus and Yield strength of UHMWPE sheet but decreases its ductility.
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Radiation grafting of a small amount of Acrylic acid (AA)
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Static contact angle of UHMWPE powder and film after gamma ray irradiation, grafting of AA and neutralization treatment.
0 kGy 100 kGy
300 kGy
Hydrophilic UHMWPE powder was prepared by radiation grafting of 5.7 wt% AA and neutralization treatment.
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Radiation grafted (amidoximation) UHMWPE fiber for uranium adsorption from seawater
AN/AAc ratio: 4/1 3:2 2:3 1:4
Simulated seawater
Marine test
Optimial ratio : AN/AAc (3/2~2/3)
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UHMWPE fiber loaded with Pd
The fiber can be applied for catalytic reduction of Cr(VI) to Cr(III)
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AcknowledgementSupported by National Natural Science Foundation of China
(NSF) (grant No. 11275252, 11305243, 21306220 and 11405249).
ConclusionRadiation technology can be applied to modify surface , creep
resistance and mechanical property of UHMWPE, and it has
industrial application.
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