Capillary rheometry of a binary mixture polymer/CO2 in a single screw extruder

Abstract

A B S T R A C TProcessing bio sourced polymers with supercritical fluids is a promising route towards new green engineering processes. Supercritical carbon dioxide (sc CO 2 ), is soluble in large quantities in molten polymers, where it acts as plasticizer and swelling agent. It is used, in blending or foaming of polymers, particle formation and polymerisation process.The process of hot melt extrusion assisted by sc CO 2 allowed the development of an on line viscosity measurement based on capillary rheometry. Applied to a bio sourced polyamide, it was validated by comparison with a classic capillary rheometer. Both data sets were in good agreement.A pseudoplastic fluid behaviour was observed with a 30 % viscosity decrease from 46 to 32 Pa s at 5000 s 1 and 220 C, upon addition of CO 2 . However, viscosity decreased to a plateau before reaching the thermodynamic solubility. The comparison with a model coupling solubility and flow allowed to identify the method limitations, which were attributed to the kinetics of dissolution and mixing. The higher the shear stress, the higher the amount of CO 2 at which the viscosity plateau is reached. These measurements may quantify the impact of the CO 2 on the rheology of the system but also of the efficiency of the mixing process in our experimental setup.

Preparation and characterization of eucalyptus wood flour/polypropylene composites by subcritical ethanol and 3‐Aminopropyltriethoxysilane as cosolvent

“…It is a continuous process with the high versatility and productivity . And it has extensively been applied in the plastic, rubber, food, and Chinese herbs industries, where it is the most important manufacturing process . Recently, supercritical fluids has been applied to the reactive extrusion by a tandem extrusion system .…”

“…Supercritical fluids assisted reactive extrusion is a viable enhancement and a new green engineering process comparing the conventional reactive extrusion for production . The supercritical carbon dioxide (SC‐CO 2 ) is usually used as the reaction extrusion medium . It is an environmentally friendly solvent, chemically inert, physiologically safe, and readily available .…”

Effect of pressurized CO2 and N2 on the rheology of PLA

“…So far, some Off-line measurements by rotational rheometers have been conducted to determine the effect that CO 2 exerts on the viscosity of amorphous P DL LA [31]. The results of this study suggested the ability of CO 2 to reduce the viscosity of PLA within a range of different temperatures (50 • C -140 • C) and pressures (5)(6)(7)(8)(9)(10)(11)(12), highlighting the advantage of using CO 2 to improve the processability of PLA and to help preventing its thermal degradation. Even so, the selection of Off-line measurements similar to the ones conducted by Kelly et al [31], entail significant differences compared to a continuous assisted-melt extrusion process.…”

“…Within these blowing agents, pressurized fluid additives (PFA) as CO 2 and N 2 have already been employed in assisted-melt extrusion processes [6,7,8,9]. For example, García-Leiner and Lesser [9] proposed the use of CO 2 to improve the processability of intractable and high molecular weight polymers thanks to its plasticization effect and its direct influence on the melting behaviour of the polymeric materials.…”

High Pressure Volumetric Properties and Viscosity of Base Oils Used in Automotive Lubricants and Their Modeling

“…While ambient pressure viscosity values are commonly determined for base oils used in automotive lubricants, very little high pressure data have been collected . Common techniques for the acquisition of viscosity data under pressure include rolling-ball/falling-body viscometers, capillary tube viscometers, and vibrational/oscillating techniques. − While all of these do have a calculable shear rate associated with the viscosity measurements, due to limitations of design, controlled variation of shear rate across a wide range is not a simple task. For these measurements, rotational viscometers have an advantage.…”