(84a) Synthesis and Processing of Polymers with Supercritical Fluids

Awareness and attention in supercritical fluids and their potential use for process improvements has expressively increased in recent years. Extraction, impregnation, chemical reactions, particle, formation of particles/fibers/foams, chemical/polymer synthesis, depolymerization, sterilization and cleaning are the major processes among many others, which have been known to successfully utilize supercritical fluids. In all these processes, the supercritical fluid is used as a substitute of traditional organic liquid solvents.

Supercritical fluids are recognized for a distinct density, viscosity, diffusivity, surface tension and other physical properties. These property values fall in between those for liquid and gas. The low viscosity, density & surface tension with higher diffusivity are special assets of supercritical fluids.

Supercritical conditions are beneficial for reactions involved in polymerization, materials synthesis, chemical synthesis, homogeneous and heterogeneous catalysis, environmental control, fuels processing, and biomass conversion. Carrying out chemical reactions at supercritical conditions offers prospects to manipulate the reaction environment with respect to solvent properties. Increasing pressure augments the reactants’ and products’ solubilities; interphase transport limitations are eliminated which increase the rates of reactions. Moreover, reaction stage and separation processes are unified.

Present work focuses on recent advances in polymer synthesis and processing using supercritical fluids. Traditional polymer synthesis techniques that are used industrially, include homogeneous systems like bulk & solution polymerization and heterogeneous systems like Suspension, Emulsion, Precipitation polymerization, Polymerization in solid state & in the gas phase. In this work, New developments on polymerization using supercritical fluids via different synthesis techniques have been reviewed. Certain advantages of supercritical fluid assisted formation of polymer blends and composites are also covered and analyzed.

An ephemeral account of the elementary operations of the several particle formation processes like, rapid the expansion of supercritical solutions (RESS), the gas antisolvent process (GAS), supercritical antisolvent process (SAS) and the particles from gas-saturated solution (PGSS) processes, is presented in this work.

The objective of this review is to underscore the gamut of opportunities available for the use of supercritical fluids as potential alternative to solvents, and as technology in polymer synthesis and particle formation from polymers.