Mechanism of Elastomeric Compositions Flow Depending on the Degree of Filling with Hydrophobic Calcium Carbonate

Abstract

The use of constant flow capillary rheometry made it possible to reveal the flow mechanisms, critical shear stresses lgτ ≥ 5,25, and the temperature range of extrusion processing of elastomer compositions. Flow mechanisms of elastomeric compositions containing calcium carbonate modified with stearic acid – 60–400 wt. parts per 100 wt. parts of rubber were studied in the temperature range of 90–180 ºС and the speed range lgγ = 1,4–2,6. It is found out that elastomeric compositions containing modified calcium carbonate 60–300 wt. parts per 100 wt. parts of rubber, can be processed in the temperature range of 140–180 °C according to the viscous flow mechanism, as the invariance of the effective viscosity dependences on the shear rate is observed. The flow curves of elastomer compositions in the speed range of lgγ = 1,4–2,6 and the temperature range of 90– 180 ºС have an inflection point: a «rod» flow is observed in the temperature range of  90–125 ºС, since a change in the strain rate has practically no effect on the value of the flow activation energy. The viscous flow mechanism is noticed in the temperature range of 125–180 ºС, while the activation energy of the flow increases from 11,87 to 18,40 kJ/mol with an increase in the shear rate from lgγ = 1,4 to lgγ = 2,6. The increase in the content of hydrophoric calcium carbonate in the elastomeric composition over 300 wt. parts per 100 wt. parts of rubber contributes to the occurence of the «cork» flow.