Two new expression functions for the X-ray diffraction profile of both crystalline and amorphous polyphenylene sulfide (PPS) have been proposed:andwhere X is the diffraction angle

Y the diffraction intensity at X

W1

W2 the left width and right width at half height

P the maximum position

A the peak height

and / the shape factor. 5=sinθ/λ

(λ is the wave length of X-ray). Function (1) is suitable for the profiles plotted against diffraction angle X

while function (2) is suitable for the profiles plotted against S.The limitation to the range of applicable diffraction angle

which is inherent to the old expression functions reported in literatures

has been eliminated in these two functions.