ELASTIC-MODULUS OF CRYSTALLINE REGIONS OF POLY(ETHER ETHER KETONE), POLY(ETHER KETONE) AND POLY(PARA-PHENYLENE SULFIDE)

Elastic moduli E1 of crystalline regions in the direction parallel to the chain axis were measured by X-ray diffraction for poly(ether ether ketone) (PEEK), poly(ether ketone) (PEK) and poly(p-phenylene sulphide) (PPS). E1 values of 71 GPa, 57 GPa and 28 GPa were obtained for PEEK, PEK and PPS, respectively. The calculated values for Treloar's method agreed well with these observed E1 values. These small E1 values were considered to be due to the fact that the lengths of the arms where the moment of force acts during the deformation are longer for these polymers than for polyethylene (PE). The deformation through bond angle bending at hetero atoms played an important contribution to the extension of the chains. The difference in E1 values among these polymers was found to depend on the difference in the bond angles and their force constants. Elastic moduli E(t) of crystalline regions in the direction perpendicular to the chain axis were also measured for PEEK and PEK. These E(t) values were somewhat larger than those for PE; however, strong intermolecular interactions were not considered to act in these polymers. The intermolecular cohesive energy and heat resistance of these super engineering plastics were able to be evaluated through the measurement of E(t) values.