Phase behavior of semicrystalline polyester resin in supercritical fluid solvents and solvent mixtures: Implications for supercritical fluid processing

Abstract

Cloud-point data between 40 and 240°C and pressures to 2750 bar are presented for a low molecular weight, semicrystalline polyester resin of 53.4 mol % adipic acid and 46.6 mol % 1,4-cyclohexanedimethanol in supercritical CO 2 , dimethyl ether (DME), and chlorodifluoromethane (CDFM), and in mixtures of CO 2 with DME, CDFM, methanol, ethanol, butanol, octanol, hexafluoroisopropanol, acetone, and cyclohexane. Carbon dioxide, by itself, is an extremely weak supercritical fluid (SCF) solvent because this polyester only dissolves at pressures in excess of 2000 bar and at temperatures over 180°C. However, DME and CDFM are excellent solvents for this polyester, which dissolves at 16 bar and 40°C in CDFM and at 167 bar and 55°C in DME. The melting point of this polyester is reduced from 105 to 40°C in CDFM and to 55°C in DME, which makes the polyester amenable to high intensity mixing for the efficient dispersion of inorganics or crosslinking agents and other hard to deposit materials.

Study of the Effect of Pressure on Melting Behavior of Saturated Fatty Acids in Liquid or Supercritical Carbon Dioxide

“…In general, supercritical carbon dioxide (SCCO 2 ) is an excellent solvent for many nonpolar (and some polar) low molecular weight compounds and selected polymers, such as amorphous fluoropolymers and silicones. , However, the solubility of numerous pharmaceutically significant excipients such as fatty acids in liquid carbon dioxide (LCO 2 ) or SCCO 2 is very low and usually requires the addition of a cosolvent. Conversely, the solubility of SCCO 2 in many polymers, fats, and fat derivatives is substantial and it acts as a plasticizer which causes a depression in melting ( T m ) or glass transition ( T g ) temperatures. − The melting point of a pharmaceutical excipient is a crucial physical property which determines its appropriateness in various pharmaceutical processes and applications . LCO 2 and SCCO 2 are known to alter the melting points of various polymers and ionic salts. , Dissolution of CO 2 increases the free volume of an excipient by dissolving into the intermolecular spaces and causing a substantial reduction in T m or T g .…”

Quantifying Plasticization and Melting Behavior of Poly(vinylidene fluoride) in Supercritical CO2 Utilizing a Linear Variable Differential Transformer

“…1,2 Supercritical CO 2 has been employed as a solvent for polymer synthesis, [3][4][5] for spin casting polymer thin films, 6 and for extraction of low molecular weight species from polymers. 1,4 In polymer melt applications, CO 2 has been used as a blowing agent for the production of foams, [7][8][9][10][11][12][13] as a processing aid to reduce polymer melt viscosity [14][15][16][17] and in facilitating fiber spinning. 18 In the solid state, supercritical CO 2 plasticization has been employed to enhance the solubility of styrene in poly(tetrafluoroethylene-cohexafluoropropene) followed by in situ polymerization of styrene to thereby produce polymer-polymer composites.…”

Melting Point Depression of Poly(ethylene oxide)-Poly(propylene oxide)-Poly(ethylene oxide) Triblock Polymers in Supercritical Carbon Dioxide in the Presence of Menthol as a Solid Co-Plasticiser

“…The knowledge of the phase behaviour of polymers in pressurised systems is of great importance, as this may enable the processing of formulations at lower temperatures to avoid the decomposition of thermolabile drugs during formulation. Investigations of the solubility or miscibility of a single solute in a binary system in contact with a single supercritical fluid (SCF) are widely reported [ 5 , 6 , 7 , 8 , 9 , 10 ]. For example, T m depression in polymers caused by the dissolution of CO 2 is very well known and has been widely reported [ 3 , 4 , 11 , 12 , 13 , 14 ].…”