Rheological Explosion in Polyethylenes with Different Chain Lengths

Appearance of the rheological explosion in PE pellets with different molecular weights is investigated. The duration of the first and second stages of the rheological explosion is almost independent of MW. The moment of irreversible destruction of the sample and the value of rheological explosion threshold linearly decrease with an increase in the length of the polymer chain. As a result of the explosion, the heat of melting of polymers with MW values equal to 3 × 105 and 1 × 106 decreases, while for PE with M = 3.5 × 104 the heat of melting remains almost unchanged. Electric current pulses are recorded. Their Fourier images are in the form of band spectra described by the Lorentz models for a damped harmonic oscillator and the Havriliak–Negami model for dielectric relaxation. Experimental data suggest that the rheological explosion is associated with the accumulation of elastic energy in the amorphous phase of PE and, during the rheological explosion, polymer chains are broken to generate radicals •RO2.