Yield and Post-Yield Behaviour of Semicrystalline Polymers: Open Issues of Practical Interest

This PhD thesis covers three different research topics in the field of science and technology of polymeric materials. They all have in common the fact that the knowledge of the yield and/or the post yield behavior is necessary for their analysis. Further, they all deal with semicrystalline polyolefins.
The first one regards the study of the yield and post-yield behavior of syndiotactic polypropylene in relation to the strain-induced structural changes.
The second one regards a methodology to characterize fracture toughness of polymeric films, the Essential Work of Fracture. The validity of this method requires that the fracture propagation occurs within plastically deformed material.
The last topic concerns a method to predict the long term failure of polymeric materials under creep loading when the plasticity controlled failure occurs.
This PhD thesis is divided in four chapters. In the first one a brief description of the main deformation mechanisms of semicrystalline polymers, as concerns polyolefins, is presented. The next three chapters deal with the topics just presented.