Evaluation of Epoxy Resin by Positron Annihilation for Cryogenic Use
The physical properties of commercially available epoxy resins for cryogenic use have been measured and were compared with the free volume evaluated by positron annihilation. The macroscopic physical properties of epoxy resin were changed by adding the plasticizer or changing the molecular weight between crosslinks. The life time of ortho-positronium were used to evaluate the free volume. The crosslinking density were changed systematically by changing the amount of plasticizer. The lifetime of ortho-positronium were used to evaluate the free volume in the epoxy resins. The different free volume dependence of macroscopic physical properties, such as fracture toughness, were found between the two systems even if the glass transition temperature was almost same. The fracture toughness of the two systems also showed the different crosslinking density dependence at liquid helium temperature. This means that the positron annihilation spectroscopy could be applicable to the molecular design of the glassy polymer epoxy resins for cryogenic use.
KeywordsFracture Toughness Free Volume Vickers Hardness Tertiary Amine Positron Annihilation
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