Polysulfone, degradation

This overall mechanistic picture has been questioned recently by Pacansky et al. (9—10) They reported virtually total elimination of S02 from PMPS films at an incident electron dose of 0.4 nC/cm1 at 25 kV with little or no loss of olefin. Olefin loss took place at much higher doses. Pacansky proposed a two-step mechanism involving S02 elimination via a chain process leaving hydrocarbon polymer which subsequently decomposed to olefin. The results are totally contrary to those previously reported by Bowden who found that at doses corresponding to 0.4 /tC/cm2 only —35% of the S02 was removed while 30% of the olefin was removed. The mechanism proposed by Pacansky et al. to explain their results is counter to the widely accepted mechanism of polysulfone degradation which is in accord with the thermodynamics of these polymers. It is difficult, for example, to conceive of a chain mechanism for S02 formation that does not include olefin formation. The "instantaneous" reformation of the... 

See also PBT degradation structure and properties of, 44-46 synthesis of, 106, 191 Polycaprolactam (PCA), 530, 541 Poly(e-caprolactone) (CAPA, PCL), 28, 42, 86. See also PCL degradation OH-terminated, 98-99 Polycaprolactones, 213 Poly(carbo[dimethyl]silane)s, 450, 451 Polycarbonate glycols, 207 Polycarbonate-polysulfone block copolymer, 360 Polycarbonates, 213 chemical structure of, 5 Polycarbosilanes, 450-456 Poly(chlorocarbosilanes), 454 Polycondensations, 57, 100 Poly(l,4-cyclohexylenedimethylene terephthalate) (PCT), 25 Polydimethyl siloxanes, 4 Poly(dioxanone) (PDO), 27 Poly (4,4 -dipheny lpheny lpho sphine oxide) (PAPO), 347 Polydispersity, 57 Polydispersity index, 444 Poly(D-lactic acid) (PDLA), 41 Poly(DL-lactic acid) (PDLLA), 42 Polyester amides, 18 Polyester-based networks, 58-60 Polyester carbonates, 18 Polyester-ether block copolymers, 20 Polyester-ethers, 26... 

The quantity R is proportional to the number of chain scissions per original macromolecule. For both PBS and PHS, for all solvents studied (1,4-dioxane, acetonitrile, chloroform, tetrahydrofuran, toluene and 2-butanone) the scattered light intensity decreases after irradiation. The amount of degradation R° for the same polysulfone is higher for solvents with larger yield of radicals. R° is larger for PHS than for PBS in the case of the solvents 1,4-dioxane and acetonitrile, which have the highest yield of radicals ... 

This paper has provided the reader with an introduction to a class of polymers that show great potential as reverse osmosis membrane materials — poly(aryl ethers). Resistance to degradation and hydrolysis as well as resistance to stress Induced creep make membranes of these polymers particularly attractive. It has been demonstrated that through sulfonation the hydrophilic/hydrophobic, flux/separation, and structural stability characteristics of these membranes can be altered to suit the specific application. It has been Illustrated that the nature of the counter-ion of the sulfonation plays a role in determining performance characteristics. In the preliminary studies reported here, one particular poly(aryl ether) has been studied — the sulfonated derivative of Blsphenol A - polysulfone. This polymer was selected to serve as a model for the development of experimental techniques as well as to permit the investigation of variables... 

Polysulfone Plastics. These plastics which were commercialized by Union Carbide are actually aromatic polyethers containing periodic sulfone groups which provide additional resonance stabilization. They have good mechanical properties, creep resistance, and dimensional stability but their outstanding quality is their high heat distortion temperature (345°F.) and resistance to thermal oxidative degradation. Limitations are difficult thermoplastic processability, amber color, and sensitivity to organic solvents. 

For many years prior to the development of high-temperature thermoplastics and thermosets, such as the polyimides. polysulfones, and epoxies, phenolic molding material dominated the high temperature-resistant market. This emphasizes their ability to resist temperature degradation in the 400-500°F (204-260 C) range. Because phenolics were found to possess excellent ablative properties, it has been reported that both the American and Soviet space efforts used them in combination with certain other... 

Figure 5. Thermal degradation of polysulfone terpolymers (weight loss after heating one hour under air)...

Loeb-Sourirajan membranes based on sulfonated polysulfone and substituted poly(vinyl alcohol) produced by Hydranautics (Nitto) have also found a commercial market as high-flux, low-rejection membranes in water softening applications because their divalent ion rejection is high. These membranes are also chlorine-resistant and have been able to withstand up to 40 000 ppm h of chlorine exposure without degradation.1 The structures of the polymers used by Hydranautics are shown in Figure 5.8. 

Chemical damage occurs when a contaminant in the feed water is incompatible with the polymer comprising the membrane, the micro-porous support, or the fabric support. Besides oxidizers that degrade the crosslinking of a thin-film membrane, there are a variety of chemicals that swell or dissolve the polysulfone microporous support, including the following compounds. 

Poly(butene-l sulfone) (PBS), a sensitive, positive, electron beam resist, is highly sensitive to 185-nm radiation (Table 3.4) (9). However, PBS does not absorb above 200 nm, and the sensitization has not been successful. Incorporation of pendant aromatic rings into the polysulfone structure extends the photosensitivity to the DUV and mid-UV regions (72). Himics and Ross (73) reported that carbonyl-containing poly(olefin sulfones) such as poly(5-hexen-2-one sulfone) are sensitive to UV-induced degradation and... 

One of the most important degradation mechanisms of SLM is an emulsification ofthe membrane phase due to lateral shear forces. Therefore, formation of barrier layers on the membrane surface by physical deposition [98] or by interfacial polymerization could prevent instability [99, 100]. A polysulfone support with N-methylpyiTolidone as a solvent was coated by a poly(ether ketone) layer as the outside layer and gave a specific composite membrane support. Such composite hoUow-fiber membranes showed significant improvement in stabUity in copper ions permeation. 

Polysulfones have found use as resists in the area of mierolithography since the polysulfones are unstable toward radiation and heat below their melting points and the SO2 and olefin degradation products are volatile. It is interesting to note that some olefins undergo isomerization during the radiation induced degradation step [9c]. 

Thermo-oxidative Degradation of Polysulfones, Polyesterketones, Liquid-Crystal Copolyesters [21, 30-39]... 

P. Almen and I. Ericsson. Studies of the thermal degradation of polysulfones by filament-pulse pyrolysis-gas chromatography. Polym. Degrad. Stabil, 50(2) 223-228,1995. 

Polysulfone has good weatherability, and it is not degraded by UV radiation. Refer to Table 2.34 for the compatibility of PSF with selected corrodents. Reference [1] provides a more comprehensive listing. 

---