Rheological Properties of Collagen Matter Predicted Using an Extrusion Rheometer

Abstract

This article reports on measurements of the rheological properties of slightly compressible collagen liquid (from 6.6 to 8.0% mass fraction of native bovine collagen in water) using a capillary rheometer. The extrusion rheometer is equipped with an annular slit between a circular tube and a central pin. The sample of collagen to be tested is pushed by a piston from a container to the annular measuring section. A manually adjusted hydraulic drive enables the piston velocity and the corresponding shear rate to be varied continuously within the range from 50 to 3000 s 21. Strain gages installed in the outer cylinder monitor the axial pressure profile. It is therefore possible to identify not only the basic nonelastic shear flow characteristics (Herschel Bulkley and Power law model parameters), but also the first normal difference evaluated from the exit pressure. The results of experiments carried out at room temperature show rather broad variability of the parameters. PRACTICAL APPLICATIONSThe rheological properties of native collagenous materials are of primary importance in the design of extrusion processes, for example, extrusion of sausage casings (a description of the flow behavior not only inside the screw extruders, but also while the extruded tubes are being blown) and similar technologies (injection molding, film blowing, rolling, and so forth). Knowledge of the rheological properties of native collagenous vascular grafts is important for an indirect assessment of irradiation effects and the effects of additives on a collagenous matrix (crosslinking). Native collagenous materials are rather "awkward" from the point of view of rheometry. For example, rotational rheometers are limited to a linear oscillation regime (due to discharge of the samples and shear banding), and the application of capillary rheometers is complicated by the inhomogeneity of native collagen (presence of bubbles). The proposed rheometer takes into account the compressibility of the tested samples, and enables an evaluation not only of the shear properties but also of the elastic properties within the range of deformation rates corresponding to the production lines.

Extrusion rheometry of collagen dough

“…Collagen has been examined at lower concentrations in the past when the structure is more liquid, and the material can therefore be tested using rotational rheometers (Micutz et al 2015;Weiss et al 2015). Similar experiments to those published in this paper have been carried out with collagen dough using capillary and slit rheometers (Skočilas et al 2016). The evaluation technique and the evaluated rheological properties were similar.…”

Analysis of Power Input of an In-Line Rotor-Stator Mixer for Viscoplastic Fluids

“…In addition to the Herschel-Bulkley model, further simulations have been carried out for the power-law model with the flow indexes ranged from 0.2 to 0.6 to examine the effect of the rheological model on k s for the investigated rotor-stator mixer with c a alue of the investigated mixeuation (12), acquired C(n) versus (1−n) curves are depicted in Figure 10 The suggested term efficiency X, defined in Equation (25), is analyzed from the acquired power draw values from the simulation and experiment for the Herschel-Bulkley model. A comparison is given in Table 2.…”

“…The water solution of the bovine collagen with a mass fraction of 7.7% and density of 1100 kg/m 3 was utilized as a test material. The rheological properties of the fluid were acquired by a capillary rheometer and rheological properties were found for the Herschel-Bulkley model as τ 0 = 4600 Pa, K = 420 Pa•s n , n = 0.34 [25]. Since the material possesses very high yield stress, a positive displacement pump (P-111) was used to discharge material from the reservoir (B-110) and feeding the mixer (M-112) with a mass flow rate of 0.1 kg/s (stream 1).…”

Simulation of collagen solution flow in rectangular capillary

“…The following calculations were performed with properties corresponding to experimental investigations [4]. The proposed parameters are given in tab.…”

“…1). On base of the previous exper- imental investigations [3,4] material constants were proposed for used water collagen solution, that are necessary as input to computational model. The proposed material properties for that case were: density ρ = 1000 kg · m −3 ; a e-mail: kysela@ih.cas.cz…”