CO₂‐assisted polymer processing: A new alternative for intractable polymers

Abstract

CO 2 -assisted polymer processing is proposed as an alternative route for intractable and high molecular weight polymers based on the plasticization effects of CO 2 and its direct effect on the melting behavior of semicrystalline polymers. A modified processing system was used to process a variety of polymers in the presence of high-pressure CO 2 . The system includes an extruder that was modified to allow for high pressures created by the injection of CO 2 . The new design includes a modified feed section that allows a given mass of polymer to interact with CO 2 before and during the extrusion process. The inherent shear mixing and the presence of CO 2 allow for a specific control over the extrudate morphology. Results suggest that this alternative design provides a new and easy route to melt process high melt viscosity polymers of commercial importance, such as polytetrafluoroethylene (PTFE), fluorinated ethylene propylene copolymer (FEP), and syndiotactic polystyrene (s-PS). The increased processability of these systems in CO 2 is related to the plasticization effect of CO 2 that was quantified through a depression in the glass-transition temperature according to the Chow model.

Polymer nano-foams for insulating applications prepared from CO2 foaming

“…Strauss and D'Souza [69] showed for a PS/CO 2 system that the condition δ 1 -δ 2 < 1 required to ensure good gas solubility, would require a saturation pressure of 90MPa at 80°C. However, many studies show that CO 2 molecules are partially soluble in polystyrene matrix (more than 13 wt% with saturation pressures lower than 20 MPa [70,71]). This is because the model does not take into account the specific chemical interactions.…”

Supercritical CO2 processing and annealing of polytetrafluoroethylene (PTFE) and modified PTFE for enhancement of crystallinity and creep resistance

“…Previous research using scCO 2 to facilitate processing resulted in foams [30,31]. In the present work, a slow vent rate was used to minimize pore generation.…”

Preparation of polymer–clay nanocomposites and their properties

“…These concepts can be utilized in the fabrication of PLS nanocomposites as a few authors have reported. 213,214 However, the extent of success is questionable and further research is needed because most authors did not investigate or report quantitatively the improvements in the materials' properties.…”