Rheometer

About: Rheometer is a research topic. Over the lifetime, 5759 publications have been published within this topic receiving 125849 citations.

The rheological characterization of linear viscoelasticity for ink jet fluids using piezo axial vibrator and torsion resonator rheometers

Abstract: This paper is concerned with the experimental ability to measure viscoelasticity of low viscosity ink jet fluids and demonstrates the capability of both a piezo axial vibrator and torsion resonator rheometer to capture high frequency rheological data for both model and commercial ink jet fluids. Results are presented for polymer and particle laden suspensions together with a commercial ink. The data demonstrate that high frequency linear viscoelastic rheology can be captured using both rheometers and that both the presence of polymer and particles can induce viscoelasticity within the fluid. It is believed that the physical origin of viscoelastic effects produced by the presence of polymer or particles is different, and this results in a different high frequency limiting slope for the G′ data.

Rheology of unsaturated polyester resins. I. Effects of filler and low‐profile additive on the rheological behavior of unsaturated polyester resin

Abstract: Measurements were taken of the bulk rheological properties of concentrated suspensions of particulates in unsaturated polyester resins, using a cone-and-plate rheometer. The particulates used were clay, calcium carbonate, and milled glass fiber. With clay and milled glass fibers, shear-thinning behavior of suspensions was observed at low shear rates or low shear stresses as the concentration of particulates was increased, whereas concentrated suspensions of calcium carbonate exhibited Newtonian behavior over the range of shear stresses or shear rates investigated. The cone-and-plate rheometer was also used for measurements of the bulk rheological properties of various mixtures of polyester resin and low-profile additives. For low-profile additives, solutions, in styrene, of poly(vinyl acetate) (PVAc) and poly(methyl methacrylate) (PMMA) were used. It was found that the bulk viscosities of all mixtures of polyester resin and PVAc solution lie between those of the individual components, whereas the bulk viscosities of some mixtures of polyester resin and PMMA solution go through a minimum and a maximum, depending on the composition of the mixture. While all mixtures of polyester resin and PVAc solution exhibited negligible normal stress, some mixtures of polyester resin and PMMA solution exhibited noticeable normal stresses. It should be mentioned that polyester resin follows Newtonian behavior. It turned out that all mixtures of polyester resin and PVAc solution exhibited clear, homogeneous solutions, whereas mixtures of polyester resin and PMMA solution exhibited optical heterogeneity, i.e., turbidity. When polyethylene powders were used as low-profile additives, suspensions of polyester resin and polyethylene powders exhibited negative values of normal stress as the concentrations of suspension reached a critical value. When both filler and low-profile additive were put together in polyester resin, the rheological behavior became quite complex, indicating that some interactions exist between the filler and the low-profile additive.

Structural time dependency in the rheological behavior of molten polymers

Abstract: In order to elucidate the role of reentanglement processes in the rheology of molten polymers, we have used the interrupted shear test and the reduction-;in-;shear-;rate test to study a linear and a branched polyethylene at 170°C. A cone-;plate rheometer was used, and shear rates were thus limited to values below 1 sec−1. For both polymers, the characteristic time for reentanglement was found to be significantly greater than the time scales associated with the relaxation of shear and normal stresses after cessation of steady shear. This observation has important implications for the modelling of melt flow in plastics processes and the evaluation of constitutive equations.