Packaging Plastics - Structure-Property Relationships

The use of various experimental methods have been widely employed to study polymer deformation. Despite these previous studies, there still remains a disconnect between the molecular architecture, i.e. branch content, molecular weight between branches, etc, and the macroscopic mechanical properties. The nature of the uniaxial deformation behavior of polymers can be explained using continuum models, a surprisingly simple yet effective example of which is the spring and dashpot model of Haward and Thackray. Such models try and interpret the observed behavior in terms of viscous and elastic components associated with the crystalline and amorphous phases within the semi-crystalline polymer regions. However, these continuum models only provide a very indirect correlation between the observed mechanical behavior and the molecular structure. In this talk, the use of in-situ X-ray scattering experiments will be discussed which have enabled development of a more complete molecular interpretation of the deformation processes in polyolefins and polyesters. These results have allowed us to make direct correlations between the molecular architecture and the mechanical properties.