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Degradation in thermal properties and morphology of polyetheretherketone- alumina composites exposed to gamma radiation
Falix Lawrence, Satyabrata Mishra, C. Mallika, U. Kamachi Mudali, R. Natarajan, D. Ponraju, Suresh Krishnamoorthy Seshadri,
Published in Springer
2012
Volume: 21
   
Issue: 7
Pages: 1266 - 1274
Abstract
Sheets of polyetheretherketone (PEEK) and PEEK-alumina composites with micron-sized alumina powder with 5, 10, 15, 20, and 25% by weight were fabricated, irradiated with gamma rays up to 10 MGy and the degradation in their thermal properties and morphology were evaluated. The radicals generated during irradiation get stabilized by chain scission and crosslinking. Chain scission is predominant on the surface and crosslinking is predominant in the bulk of the samples. Owing to radiation damage, the glass transition temperature, T g increased for pure PEEK from 136 to 140.5 °C, whereas the shift in T g for the composites decreased with increase in alumina content and for PEEK-25% alumina, the change in T g was insignificant, as alumina acts as an excitation energy sink and reduces the crosslinking density, which in turn decreased the shift in T g towards higher temperature. Similarly, the melting temperature, T m and enthalpy of melting, ΔH m of PEEK and PEEK-alumina composites decreased on account of radiation owing to the restriction of chain mobility and disordering of structures caused by crosslinks. The decrease in T m and ΔH m was more pronounced in pure PEEK and the extent of decrease in T m and ΔH m was less for composites. SEM images revealed the formation of micro-cracks and micro-pores in PEEK due to radiation. The SEM image of irradiated PEEK-alumina (25%) composite showed negligible micro-cracks and micro-pores, because of the reinforcing effect of high alumina content in the PEEK matrix which helps in reducing the degradation in the properties of the polymer. Though alumina reduces the degradation of the polymer matrix during irradiation, an optimum level of ceramic fillers only have to be loaded to the polymer to avoid the reduction in toughness.©ASM International.
About the journal
JournalData powered by TypesetJournal of Materials Engineering and Performance
PublisherData powered by TypesetSpringer
ISSN10599495
Open AccessNo
Concepts (23)
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    ALUMINA COMPOSITES
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    ALUMINA CONTENT
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    Alumina powder
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    CERAMIC FILLERS
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    CHAIN MOBILITY
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    CHAIN SCISSION
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    Cross-linking density
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    CROSSLINKS
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    HIGH ALUMINA
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    Micropores
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    REINFORCING EFFECTS
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    Sem image
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    Alumina
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    Cracks
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    Degradation
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    Ethers
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    Gamma rays
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    Irradiation
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    Morphology
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    Polyether ether ketones
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    Radiation damage
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    Thermodynamic properties
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    Polymer matrix composites