Effects of β-α transformation on the static and dynamic tensile behavior of isotactic polypropylene

摘要: It was demonstrated that the mechanical stress-induced βα-transformation in isotactic polypropylene (iPP) is associated with considerable toughness enhancement. This improvement depends on test conditions (loading frequency). The of β-iPP superior to α-iPP by 13% under static (characterized a load frequency ca. 5 × 10−4 Hz) and 70% dynamic (tensile impact loading range 3 102…103 conditions, respectively. By applying essential work fracture (EWF) concept single-edge notched tensile (SEN-T) specimens it shown for upgrading observed, energy dissipation enlarged plastic zone responsible. occurrence evidenced differential scanning calorimetry (DSC). Based DSC measurements found degree βα-trans-formation local strain. At high strain values βα-conversion complete (at elogation at break uniaxial test), while this transformation only partial lower strains impact). In addition, (or deformation) changed locally, can be used mapping region. © 1996 John Wiley & Sons, Inc.