Elastic moduli of crystalline regions of poly(ether ether ketone).

Abstract

Elastic moduli of crystalline regions of poly (ether ether ketone)_??_(PEEK) in the direction parallel (El) and perpendicular (Et) to the chain axis were determined by X-ray diffraction. The observed moduli Et are as follows; (110); Et=5.9 GPa, (200); Et=4.2 GPa, (020); Et=5.0 GPa. The Et value for the (200) plane is nearly equal to that of polyethylene (ca. 4 GPa). This means that there is no especially strong interaction other than dispersion forces in this direction. But Et values for the (020), (110) planes are somewhat large. This is considered to be due to the dipole-dipole interactions between ether (carbonyl) linkages, since these functional groups are superposed upon each other in these directions. On the other hand, different orders of meridional reflections give different El values (31, 57, 71 GPa for (002), (006) and (008) plane, respectively). This phenomena may be due to the increase of the crystallite size by the applied stress. Judging from the similarity to the calculated El value (69 GPa), it seems that the El value for the (008) plane (71 GPa) is valid, from which the force required to stretch a molecule by 1% can be calculated as 1.64×10-5 dyne.