Quantitative structural characterization of the mechanical properties of isotactic polypropylene

This investigation introduces quantitative morphological criteria for defining the structural state of a polymer sample and develops a general structural state deformation model for characterizing mechanical behavior. This general model discards the present fragmented view of the autonomy of observed mechanical processes (yielding, fracture, recovery, etc.) and brings the fabrication process, the mechanical tests, and even the construction of the sample (fiber or film) into focus as simply different aspects of a single process of deformation. The fabrication, fracture, yielding, and recovery behavior of two series of uniaxially drawn isotactic polypropylene films and two series of drawn isotactic polypropylene fibers, totaling thirty different structural states, have been deter-mined. The structural state of each of these samples is known quantitatively. The measurements were made over a range of strain rates from 1 to 1,000,000%/min and temperatures from 23° to -196°C. This study has resulted in new quantitative relationships between mechanical properties and morphological structure and has developed a deeper insight into the underlying deformation mechanisms that are occurring.