Structure and morphology of polyolefin materials and coatings

 
Crystalline polyolefins are complex materials. Their structure and morphology must be analyzed at length scales ranging from angströms to micrometers or even millimeters. It covers different aspects: configuration, conformation (frequently helical), packing of the chains in unit-cells and in chain folded lamellae, and organization of the lamellae in various structures: spherulites, transcrystalline layers, etc. Deciphering these different levels has required a combination of experimental techniques (X-ray and electron diffraction, microscopy, etc) but the field has now reached a stage where, in favorable cases, the connection can be established between very local, sub-molecular processes and much larger scale morphological features. At the same time, the "spontaneous" morphologies can be manipulated by e.g. processing conditions and nucleating agents. These aspects will be mostly illustrated with polyethylene and isotactic polypropylene.