Rheology of Wet Pastes of Pvc Particles

Abstract

The present work deals with the study of the rheological behaviour of PVC (polyvinylchloride) pastes containing particles of ≈ 150 mm in diameter obtained by polymerization in suspension. The rheological properties of the PVC pastes were characterized by creep experiments using 6-bladed vane geometry. The pastes show a very small compliance and a very narrow linear domain. The effects of temperature, of interstitial liquid and of saturation level of the wet paste were studied in detail and it was found that they significantly modify the creep behaviour. Other techniques allowed us to characterise rearrangements of the particles under load, in compression, by their oedometric modulus and by the failure stresses measured using a shear box. A very high oedometric modulus was measured (20 MPa) and by application of the Mohr-Coulomb criterion the internal friction coefficient (m ≈ 0.6) and the cohesion of the materials were deduced. We conclude from this investigation that the interfacial properties of the grains play a major role in the behaviour of the wet pastes under shear or in compression. The paper illustrates the difficulties in measuring the rheological and the structural properties of jammed systems made from non-ideal (real) particles and reveals the key parameters in studying such media.

Keywords

• pvc
• wet paste
• jammed systems
• creep
• failure
• oedometric modulus
• shear box
• saturation effects