Effect of annealing on viscoplasticity of polymer blends: Experiments and modeling

Observations are reported on polypropylene/polyethylene blends with various concentrations of components in uniaxial tensile tests at ambient temperature. Three types of blends are analyzed: (i) non-annealed, (ii) annealed below the melting temperature of polyethylene, and (iii) subjected to thermal treatment above this temperature. A constitutive model is developed for the viscoplastic behavior of polymer blends that treats a semicrystalline polymer as a two-phase composite medium. The stress-strain relations involve four adjustable parameters that are found by fitting the observations. The model is applied to examine the effect of annealing on elastic moduli of amorphous and crystalline phases.