Prediction of the viscosity reduction due to dissolved CO2 of and an elementary approach in the supercritical CO2 assisted continuous particle production of a polyester resin

Abstract

The dissolution of CO 2 in a polymer causes plasticization of the polymer and hence, its viscosity is reduced. A model based on the free volume theory has been used for a polyester resin, which shows a considerable reduction in the viscosity due to dissolved CO 2. Therefore, supercritical CO 2 has been used as a processing solvent in the continuous production of micron size particles of the resin. Despite the viscosity reduction caused by the dissolved CO 2 , an excess quantity of CO 2 with respect to its solubility limit has been used for micronisation of the polymer due to its high viscosity. The mixing of CO 2 and the polymer has not been possible in an extruder at high gas to polymer mass ratios and consequently, a simplified Kenics type static mixer has been used for the mixing purpose. In this study, the effect of various parameters such as temperature, pressure, nozzle diameter and gas to polymer mass ratio on the particle morphology and size has been studied. The experimental results manifest the technological as well as the theoretical insight into the particles production from a high viscosity material.

Controlling the structure of a porous polymer by coupling supercritical CO2 and single screw extrusion process

“…At higher CO 2 concentrations (above 0.1 %), the small cell density and the macroporosity may be explained by an outmost predominant growth phenomenon but also probably a heterogeneous polymer‐CO 2 blend in the extruder for some CO 2 concentrations where CO 2 could be present in excess. Consequently, this favors nucleation around the existing bubbles and their growth and this enhances the macropores development to the detriment of the small pores 32…”

Viscosity studies of poly(DL‐lactic acid) in supercritical CO2

“…This has an adverse effect on the free volume and consequently, forces the polymer chains closer together again. 14 The latter effect becomes more dominant as the pressure is increased to 12 MPa, reducing the effect of the CO 2 diffusion on the viscosity. A similar trend has also been observed with P DL LA (M w 52 kDa, Purac) following shear thinning in scCO 2 .…”

“…The use of scCO 2 to produce polymer particles via the particles from gas saturated solutions process is also well documented with the reduction in viscosity, facilitating the atomization of polymers through a nozzle. [13][14][15] Lyons et al also noted a viscosity reduction when extruding poly(ethylene glycol) and the methacrylate-based copolymer, Eudragit in the presence of scCO 2 as evident by a 20-30% reduction in both the die head pressure and torque within the barrel. 16 The unique gas-like density and liquid-like viscosity of scCO 2 enables it to diffuse into the free volume between polymer chains.…”

Modification of polystyrene properties by CO2: Experimental study and correlation

“…Next, the influence of the CO 2 sorption on the modification of the PS properties is studied. The sorption of CO 2 in Polystyrene produces polymer swelling, large depression in glass transition temperature, interfacial tension, and viscosity . Experimental measurements of the glass transition temperature and viscosity and interfacial tension data summarized from the literature are related with the experimental sorption of the gas molecule in the polymer.…”