The application of7a,14c-dihydronaphtho[2,1-
b]naphtho[2',1':4,5]furo[3,2-
d]furan(FF) wasinvestigated as an effective stabilizer for polystyrene (PS) at highertemperatures. PS containing1% FF retained 97.9% of its tensile strength (Ts) after heattreatment at 190
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C for 90 min inthe absence of oxygen and 95% of Ts heated at 160
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C for 150 min inair and molded at 160
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Cfor 90 min under reduced pressure, whereas PS without stabilizers lostTs by 50% under theformer treated condition and 20% under the latter one. Theeffectiveness of FF as a heatstabilizer for PS was confirmed by thermal analyses (TG and DSC), inair and in nitrogen. Apossible stabilization mechanism was studied by IR spectroscopy and MOcalculation. Theformation of a stable radical from FF was observed by ESRspectroscopy.