Improvement in polypropylene thermal oxidative stability by annealing under an inert atmosphere

Zlatkevich, Lev

doi:10.1002/pol.1985.180231219

Cited by 19 publications

(3 citation statements)

References 6 publications

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“…8,9 In this case, some of the crystalline regions are melted and the free radical content is reduced, but is still detectable. 10,11 One first generation of highly crosslinked and annealed UHMWPE implants was terminally gamma sterilized and therefore had a significant amount of detectable free radicals, leading to oxidation in vivo .…”

Section: Introductionmentioning

confidence: 99%

The elimination of free radicals in irradiated UHMWPEs with and without vitamin E stabilization by annealing under pressure

2011

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Radiation crosslinking of ultrahigh molecular weight polyethylene (UHMWPE) has been used to decrease the wear of joint implant bearing surfaces. While radiation crosslinking has been successful in decreasing femoral head penetration into UHMWPE acetabular liners in vivo, postirradiation thermal treatment of the polymer is required to ensure the oxidative stability of joint implants in the long term. Two types of thermal treatment have been used: (i) annealing below the melting point preserves the mechanical properties but the residual free radicals trapped in the crystalline regions are not completely eliminated, leading to oxidation in the long-term and (ii) annealing above the melting point (melting) eliminates the free radicals but leads to a decrease in mechanical properties through loss of crystallinity during the melting process. In this study, we hypothesized that free radicals could be reduced by annealing below the melting point under pressure effectively without melting due to the elevation of the melting point. By avoiding the complete melting of UHMWPE, mechanical properties would be preserved. Our hypothesis tested positive in that we found the radiation-induced free radicals to be markedly reduced (below the detection limit of state-of-the-art electron spin resonance) by thermal annealing under pressure in radiation crosslinked virgin UHMWPE and UHMWPE/vitamin-E blends without loss of mechanical properties.

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Section: Introductionmentioning

confidence: 99%

The elimination of free radicals in irradiated UHMWPEs with and without vitamin E stabilization by annealing under pressure

2011

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“…The next step in the argument is to write the maximum intensity of the OL in the form Since the same constant C is used in eqs. (15) and (16) this implies that the maximum emission occurs only when every tertiary carbon atom in the polymer bears a hydroperoxide group. While the maximum conceivable luminescence could correspond to the conversion of all of the polymer repeat units to hydroperoxides, it is experimentally found that the maximum concentration of hydroperoxides in a polymer is very much lower.…”

Section: Problems With the Kinetic Modelmentioning

confidence: 97%

Chemiluminescence from oxidation of polypropylene: Some comments on a kinetic approach

Billingham

George

1990

J Polym Sci B Polym Phys

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SynopsisWe present a detailed criticism of the kinetic approach to the analysis of data obtained from measurements of the very weak chemiluminescence accompanying the oxidation of polypropylene. It is shown that a kinetic model proposed by other workers is based upon invalid assumptions, leads to kinetic parameters which are not sensible, and requires measurement of the properties which it claims to predict.

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“…Annealing tended to distribute the molecules of the stabilizer into higher molar mass domains, and the induction period of oxidation increased. Other authors suggested that during annealing in an inert atmosphere, other reactive sites such as hydroperoxides and terminal unsaturations were removed, which allowed polymer of a better quality to be obtained [46].…”

Section: Stabilized Polymer Systemsmentioning

confidence: 99%

Chemiluminescence Processes in Polymeric Materials

Corrales

Peinado

Abrusci

et al. 2010

Photochemistry and Photophysics of Polymer Materials

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Improvement in polypropylene thermal oxidative stability by annealing under an inert atmosphere

Cited by 19 publications

References 6 publications

The elimination of free radicals in irradiated UHMWPEs with and without vitamin E stabilization by annealing under pressure

The elimination of free radicals in irradiated UHMWPEs with and without vitamin E stabilization by annealing under pressure

Chemiluminescence from oxidation of polypropylene: Some comments on a kinetic approach

Chemiluminescence Processes in Polymeric Materials

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