Study of different peroxide types on the modification of LLDPE. Part 1. Factorial experimental design and thermal properties

A commercial-grade linear low-density polyethylene (LLDPE) resin was modified using different peroxide types. The effect of two peroxides types (Trigonox 101 and Perkadox 14-40B-PD) on the molecular weight of LLDPE during a reactive extrusion process was studied. The influence of the peroxide type and the processing conditions were investigated using a factorial experimental design. The dependent variable studied was melt flow index (MFI). Preliminary results showed that the most significant processing variables were screw speed rate (30 rpm) and peroxide type, 0.07% w/w (Trigonox 101). The more important observation of this work was that peroxides with similar half-lifetimes and the same ultimate active free-radical species can exhibit very different behavior in the same polymer system. The choice of the best peroxide for a particular application should not be made entirely on the basis of the peroxide degradation rate at a specified temperature. In addition, Trigonox 101-treated samples exhibited crystalline melting temperature (Tm), heat of fusion (ΔHmelt) and degree of crystallinity (X%) decreasing with the increase of the peroxide concentration, while the crystallization temperature (Tc) increased up to 0.05% w/w peroxide.