Dynamic mechanical thermal analysis of all-PP composites based on β and α polymorphic forms

All polypropylene (all-PP) composites were manufactured by exploiting the polymorphic forms of PP, in which alpha (α)-PP tapes worked as reinforcement and beta (β)-PP served as matrix. The mechanical performance of the composite was investigated in a range of frequencies and temperatures using dynamic mechanical thermal analysis (DMTA). The volume fractions of matrix and reinforcement were estimated using optical microscope images. Both the DMTA and the static flexural bending tests revealed that the α-PP tapes act as an effective reinforcement for the β-PP matrix. Time–temperature superposition (TTS) was applied to estimate the stiffness of the composites as a function of frequency (f = 10−9...1023) in the form of a master curve. The Williams–Landel–Ferry (WLF) model described properly change in the experimental shift factors used to create the storage modulus versus frequency master curve. The activation energies for the α and β relaxations were also calculated by using the Arrhenius equation.