Polyethersulphone

The cooling requirements will be discussed further in Section 8.2.6. What is particularly noteworthy is the considerable difference in heating requirements between polymers. For example, the data in Table 8.1 assume similar melt temperatures for polystyrene and low-density polyethylene, yet the heat requirement per cm is only 295 J for polystyrene but 543 J for LDPE. It is also noteworthy that in spite of their high processing temperatures the heat requirements per unit volume for FEP (see Chapter 13) and polyethersulphone are, on the data supplied, the lowest for the polymers listed. 

Figure 9.9. Curves for creep in tension of a commercial polysulphone (Polyethersulphone 300P-ICI) at 20°C. (From ICI Technical Service Note PES 101, reproduced permission of ICI Plastics...

Very low smoke emission, superior even to polyethersulphone. 

The first commercial polymer Table 21.3, II) was offered in 1965 by Union Carbide as Bakelite Polysulfone, now renamed Udel. In 1967 Minnesota Mining and Manufacturing introduced Astrel 360 Table 21.3, V), which they referred to as a polyarylsulfone. In 1972 ICI brought a third material onto the market which they called a polyethersulphone (III) and which they then marketed as Victrex. They also introduced a material intermediate between III and V known as Polyethersulphone 720P (IV) but which has now been withdrawn. In the late 1970s Union Carbide introduced Radel (VI), which has a higher level of toughness. Around 1986 Union Carbide sold their interest in polysulphones to Amoco. In addition the Astrel materials were produced by Carborundum under licence from ICI. 

The differences between the main types of polysulphone are quite small. The polyethersulphones (Type III in Table 21.3) have markedly better creep resistance at elevated temperatures, e.g. 150°C, significantly higher heat distortion temperatures and marginally superior room temperature meehanical properties than the Type II materials. They also exhibit higher water absotption, dielectric constant and specific gravity. 

Polyacetal Homopolymer Polyelherimide Phenolic Resin Polypropylene Polyvmylidene Difluonde Polyphenylene Oxide Polyphenylene Oxide (Glass Filled) Polyethersulphone I ill ll I i jH... 

Polyethersulphone is the term given to certain polysulphones of improved heat resistance introduced by ICI. (In fact all commercial polysulphones are polyethersulphones.) Commercial polymers now have values of ranging from 190 to 285°C, but the cost generally increases sharply with T, and those at the higher end of the range may only be available to special order. 

Polyether ether ketones (PEEK) have been developed using polyethersulphone technology. These materials crystallise, unlike the polysulphones, and have higher maximum service temperatures. They also have better resistance to hydrolysis at elevated temperatures than the polymides. 

DMTA is a very interesting tool for characterizing heterogeneous materials in which domains of distinct Tg values coexist. The most interesting cases involve modified thermosets of different types (see Chapter 8). Examples are the use of rubbers (e.g., liquid polybutadiene and random copolymers), or thermoplastics (e.g., polyethersulphone or polyetherimide in epoxy matrices or poly(vinyl acetate) in unsaturated polyesters), as impact modifier (epoxies), or low-profile additives (polyesters). The modifier-rich phase may be characterized by the presence of a new a peak (Fig. 11.10). But on occasions there may be superposition of peaks and the presence of the modifier cannot be easily detected by these techniques. If part of the added polymer is soluble in the thermoset matrix, its eventual plasticizing effect can be determined from the corresponding matrix Tg depletion, and the... 

Fig. 14.9. Normalised force (F/R R is the particle radius) vs piezo displacement plot (retraction) for a polystyrene colloid probe in 0.01 M NaCI at pH 8.0. (a) Conventional polyethersulphone membrane, (b) Modified mixed polymer membrane.

Other examples of solvent effects in casting blends include epoxy resin/copoly-ester/tetrachloroethane polyethersulphone/poly(ethylene oxide)/cyclohexanone and mixtures of PVC with various polyacrylates in solvents such as THF One particular pair of polymers PVC/poly(ethyl acrylate) appear to be miscible but no suitable solvent has been found as yet. Homogeneous blends can only be prepared by in situ polymerisation though it is possible that miscibility is enhanced by small amounts of graft copolymer which is inevitably formed by this technique. 

These conclusions are similar to those of Gans, who performed beer CMF experiments with a polyethersulphone hollow fiber membrane of 0.45 pm nominal pore size [12]. He did observe a shght increase of the permeate flux when increasing TMP up to -4 bar (400 kPa) (Figure 20.7), but increasing the TMP to 5-6 bar (500-600 kPa) resulted in a negative effect on the permeate flux (Figure 20.8). The same effect is observed in industrial scale installations. 

A recent study has shown that membranes made of a modified polyetheretherketone (PEEK-WC) are interesting materials for biomedical applications [23,24]. The cytocompatibility of PEEK-WC membranes was evaluated by culturing hepatocytes isolated from rat liver (Figure 43.6). The properties of PEEK-WC membranes were compared to polyurethane membranes prepared using the same technique, and commercial membranes (made of Nylon, polyethersulphone, and polyester). The results have shown that PEEK-WC membranes promoted hepatocyte adhesion most effectively and metabolic activities of cells cultured on these membranes improved significantly. 

The hollow fibre is the most crucial part of the microdialysis probe. It acts as a membrane, and its characteristics affect performance in the sampling step as well as the probe s suitability for the selected application. Hollow fibres are commercially available in different materials, the most common being polycarbonate (PC), regenerated cellulose (Cuprophan, CU), cellulose acetate (CA), polyacrylonitrile (PAN), polyethersulphone (PES), polysulphone (PE), and polyamide (PA). Generally, the fibres have an outer diameter between 200... 

Bucknall, C.B. Patridge, I.K. Phase separation in epoxy resins containing polyethersulphone. Polymer 1983, 24, 639-644. 

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