Molecular Analysis of the Mechanical Behavior of Plasticized Amorphous Polymers

Plasticization effects on the mechanical behavior were investigated on two families of materials based on poly(methyl methacrylate) (PMMA) and poly(vinyl chloride) (PVC), respectively. For this purpose, PMMA was blended with poly(vinylidene fluoride) (PVDF) by co-precipitation from solution, all over the PVDF range 0-40 wt% where the samples remain amorphous. Di-octylphtalate (DOP) was mechanically dispersed in PVC over the DOP range 0-20 wt%. The relaxation behavior of the samples was studied by differential scanning calorimetry at heating rate of 10 deg C.min-I and by dynamic mechanical analysis at the frequency 1 Hz over the temperature range -100 deg C1150 deg C. Stress strain curves were recorded during compression testing at a deformation rate of 2.10-3 s-I . Data analysis was carried out on the molecular scale; it permitted to highlight the influence of the /3 relaxation motions on the plastic behavior. Consideration of the non elastic part of the energy to yield was clearly related to the contribution of a and /3 motions.