Rates of property change in plasticized filled PVC compounds

Abstract

AbstractRheological and mechanical properties of polyvinyl chloride (PVC) compounds vary with the polymer entanglement state at the time of testing. Controlled shearing episodes and thermal histories applied to the compounds produce major property variations. These then relax toward steady‐state values at rates which are consistent with diffusion‐controlled processes, presumably connected with the development of steady‐states in entanglement couplings. Activation energies of 4–7 kcal/mol apply to the proposed re‐entanglement processes. Rates of property variation can be altered by the addition of fillers to the compounds, the interactions between polymer and filler being an important factor in this regard. CaCO3 samples with strong affinity for the PVC retard the rate of property variations (i.e., the filler tends to stabilize non‐steady‐state entanglement couplings). Fillers, surface treated so as not to interact strongly with the polymer, produce lesser effects on relaxation rates. The data indicate the feasibility of controlling both the sensitivity of polymer properties to processing variables, and the rates of property change associated with the attainment of steady‐state polymer entanglement morphologies.