Birefringence, infra-red dichroism and shrinkage-stress data of poly(aryl ether ether ketone) (PEEK) uniaxially drawn above the glass transition have been analysed in the framework of the theory of rubber elasticity. It is shown that PEEK chains having a molecular weight M,~13000 only contain three entanglements per chain on average. The very low level of shrinkage stress of the samples having a draw ratio below the threshold of strain-induced crystallization is perfectly consistent with a weakly entangled network. The birefringence versus stress curve discloses an orientation-dominated regime at low strains and a deformation-dominated regime starting from the onset of the strain-induced crystallization. The length of the random link, L= 1.8 nm, is in very good agreement with the one that can be theoretically predicted for the stiff-chain polymer relatives, poly(ethylene terephthalate), polycarbonate and poly(phenylene oxide). A value for the intrinsic birefringence of the amorphous phase, An~ = 0.38_ 0.04, is also reported
Посилання на статтю:
Tensile drawing of poly(aryl ether ether ketone): 1. Birefringence, infra-red dichroism and shrinkage-stress measurements / Veronique Bassigny and Roland Segue1a and Franteois Rietsch // Polymer. – 1993. – Vol 34. – P. 4052-4059.