Polysulfone processing conditions

High-temperature thermoplastics, such as polysulfone, polyether sulfone, polyphenylene sulfide, polyether imide, polyaryl ether ketone, and polyphenylene ether are processed at high temperatures (some above 300 °C). Here, the limit of pyrolysis is almost reached. Degradation and cross-linking as well as discoloration can occur thermal-oxidative and thermal-mechanical degradation under processing conditions have not been sufficiently investigated [38]. 

PBI and polysulfone (PS) do not form miscible blends, but the tensile modulus and strength of their blend fibers were found to be comparable to, or better than, that of PBI fibers, depending on the process conditions. Fiber spun from 80/20 PBl-PS solution blends were found to have PBl-hke hm-iting oxygen indices (LOl) and flame shrinkage behavior. The 80/20 blend fibers were found to have comparable or superior mechanical performance to that of miscible PBl-Ultem blend fibers, and with higher modulus but lower elongation than stabilized PBI. 

In the petroleum industry, dewaxing solvents are separated by ultrafiltration from dewaxed oils by chemically resistant membranes made from polysulfone or polyimide. In a related process, pentane is separated from deasphalted heavy oil under conditions intermediate between reverse osmosis and ultrafilttation (ca. 15 bar applied pressure). High-molecular-weight hydrocarbons in the oil form a gel layer on the surface of a polysulfone support membrane. This gel restricts passage of heavier hydrocarbons but not pentane, which is recovered as permeate. To separate other hydrocarbon mixtures that do not contain gel-forming components, polymeric additives would be used as a rejecting barrier substitute. 

Japanese investigators reported that liquid sulfur dioxide polymerizes styrene derivatives (e.g., p-methyl styrene, a-methyl styrene) (19). Unfortunately, the experiments were not executed under rigorously anhydrous conditions (high vacuum) so that the possibility for proton (e.g., sulfurous or sulfuric acid) initiation exists although the authors seem to believe that S02 is the catalyst, probably by the following process 2S0a SO2 +SO e. The cationic nature of the mechanisms was proven by the facts that no polysulfones formed, that the polymerization was inhibited by bases, and that free radical inhibitors did not affect the reaction. These authors also claim that formaldehyde is polymerized by sulfur dioxide to a product which does not contain sulfur and whose infrared spectrum closely resembles that of a low temperature sample. 

Membrane materials for reverse osmosis and ultrafiltration applications range from polysulfone and polyethersulfone, to cellulose acetate and cellulose diacetate [12,18-23]. Commercially available polyamide composite membranes for desalination of seawater, for example, are available from a variety of companies in the United States, Europe, and Japan [24]. The specific choice of membrane material to use depends on the process (e.g., type of liquid to be treated and operating conditions) and economic factors (e.g., cost of replacement membranes and cost of cleaning chemicals). The exact chemical composition and physical morphology of the membranes may vary from manufacturer to manufaemrer. Since the liquids to be treated and... 

The processing of plasma derivatives with ultraliltration is usually conducted in cold rooms. For albumin processing, cassettes and spirals with 10 kDa polysulfone and polyethersulfone membranes have been used to remove the 40% ethanol as quickly as possible and for concentrating the protein to the final concentration of 25%. Typically, 4—5 diafiltration volumes are used to remove ethanol. For high concentration HSA formulations (25%), the protein is first concentrated to 12%, diafiltration conducted under constant volume conditions at that concentration and the protein subsequently concentrated to 25% [21,22]. Typical fluxes for albumin range between 50 and 100 Lmh with operating TMPs ranging between 30 and 50 psi. 

Side Reactions during Sulfonation. A major object in choosing a suitable sulfonation reagent and process is the avoidance of undesired side reactions the nature and extent of which will depend upon the structure of the compound being sulfonated, the sulfonating agent, and the physical conditions used. The principal side reactions encountered with aromatic compounds are sulfone formation, polysulfonation, formation of undesired isomers, and oxidation. Anhydride formation, dealkylation, and rearrangement have also been noted. 

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