Ss. Tan et al., Effect of physical aging on the microstructure and the crystallization of amorphous poly(aryl ether ether ketone ketone) (PEEKK), MACRO CH P, 200(11), 1999, pp. 2487-2493
Physical aging of poly(aryl ether ether ketone ketone) (PEEKK) has been inv
estigated. Heat flow responses were measured after annealing the amorphous
samples obtained by quenching the melt into an ice-water bath close to, but
below, the glass transition temperature. The extent of aging is related to
the supercooling from the glass transition temperature and to the aging ti
me. The activation energy of the aging process, which was estimated by a Wi
lliams-Watt expression, is similar in magnitude to that obtained for the co
ld crystallization for the aged samples. The quenched glass is a metastable
glass. The conformation of molecular chains rearranges with physical aging
which results in the formation of a denser packing in the amorphous phase.
The dense amorphous phase may form an initial nucleus for crystallization.
Isothermal cold crystallization of the aged samples was carried out. The A
vrami equation was used to determine the kinetic parameters, and the Avrami
constant n is about 2. An Arrhenius expression was used to evaluate the ac
tivation energy of relaxation upon physical aging and the activation energy
of transportation upon isothermal crystallization. The activation energy o
f relaxation is similar in magnitude to that of crystallization for aged sa
mples. Results obtained are interpreted as kinetic effects associated with
the glass formation process.