Anisotropic linear thermal expansivity of poly(ether-ether-ketone)

This paper deals with anisotropic behavior of thermal expansivity (alpha) of poly(ether-ether-ketone) (PEEK) sample prepared by compression molding above the melting point of polymer. The alpha was determined using thermo mechanical analyzer (TMA) for the temperature interval 50-250 degrees C in expansion mode. It is found that out-of-plane thermal expansivity (alpha(z)) is 3.8-fold of the in-plane thermal expansivity (alpha(xy)) below the glass transition temperature (T-g) of PEEK while alpha(z) is decreased to 1.8-fold of the alpha(xy) above the T-g Moreover, the average alpha(z) over the range studied is about 2.2-fold of the alpha(xy), This anisotropic behavior may be attributed to the alignment of polymer spherulites and chains along in-plane direction due to compressive forces under hot compression molding. (c) 2006 Elsevier Ltd. All rights reserved.