X-ray crystallographic studies of polymeric materials

361-366X-ray diffraction (XRD) studies are very useful for distinguishing crystalline and non-crystalline states. Highly crystal line substances give patterns with sharp diffraction peaks or spots, whereas liquids or amorphous materials lie between these two extremes, because their chain length is large and it is difficult to attain three-dimensional regularity. However, XRD studies of polymers yield interesting results. A large number of polymeric materials such as polyethylene, polypropylene, nylon, polyethylene terephthalate (PET), polyvinylidine fluoride etc. as well as natural polymers like, cotton and silk have been studied. The diffraction pattern usually consists of some sharp peaks together with broad halos. A careful analysis of the diffraction pattern allows us to find out the crystallite shapes, sizes and percentage crystallinity. The diffraction pattern is very sensitive to thermal history, chemical processing and other factors. In the present paper, the results of XRD of PET when subjected to thermal , chemical and plasma treatments have been presented. The results show that the percentage crystallinity can be varied from 17 to 50 %.