As　a　special　engineering　material,　poly(ether-ether-ketone)　(PEEK)　is　widely　used　in　various　safety　facilities　of　nuclear　power　plants　and　is　susceptible　to　the　long-term　cumulative　effects　of　many　complex　factors.　Among　them,　heat　and　irradiation　are　two　key　accompanying　factors　that　accelerate　the　degradation　of　PEEK　materials.　Long-term　exposure　to　heat　and　irradiation　can　lead　to　cracking,　cross-linking,　and　oxidation　reactions　of　PEEK　materials,　impairing　material　properties,　reducing　device　and　operational　reliability,　and　even　shortening　service　life.　Therefore,　it　is　very　important　to　study　its　thermal-radiation　aging　law　for　its　material　service　optimization.　In　this　study,　PEEK　sheets　with　different　tensile　orientations　were　irradiated　by　a　cobalt-60　irradiation　source　in　an　air　atmosphere　at　70　degrees　C,　and　the　effect　of　thermal-radiation　on　the　properties　of　PEEK　sheets　was　studied.　Fourier　transform　infrared　spectroscopy　(FTIR),　X-ray　diffraction　(XRD),　differential　scanning　calorimetry　(DSC),　thermogravimetric　analysis　(TGA),　scanning　electron　microscopy　(SEM),　and　universal　tensile　machine　were　used　to　investigate　the　effect　of　absorbed　dose　on　the　crystalline　properties,　thermal　stability,　mechanical　properties　and　surface　morphology　of　oriented　PEEK　sheets　in　the　direction　of　force　(horizontal　direction)　and　perpendicular　to　the　direction　of　force　(vertical　direction).　Results　showed　that　the　physicochemical　properties　of　the　oriented　PEEK　sheets　were　changed　under　the　synergistic　effect　of　temperature,　air,　and　irradiation.　Within　the　absorbed　dose　range,　with　the　increase　of　absorbed　dose　from　0-2500　kGy,　the　crystallinity　of　the　sample　first　increased　and　then　decreased.　Due　to　the　predominance　of　chain　scission　in　the　aging　process,　the　crystallization　temperature　and　melting　temperature　of　the　sample　increased,　while　the　thermal　stability　decreased.　Elongation　at　break　and　tensile　strength　decrease　with　increasing　absorbed　dose.　(c)　2022　Elsevier　B.V.　All　rights　reserved.