Polysulphones stability

As with the polysulphones, the deactivated aromatic nature of the polymer leads to a high degree of oxidative stability, with an indicated UL Temperature Index in excess of 250°C for PEEKK. The only other melt-processable polymers in the same league are poly(phenylene sulphides) and certain liquid crystal polyesters (see Chapter 25). 

Membranes used for the pressure driven separation processes, microfiltration (MF), ultrafiltration (UF) and reverse osmosis (RO), as well as those used for dialysis, are most commonly made of polymeric materials. Initially most such membranes were cellulosic in nature. These ate now being replaced by polyamide, polysulphone, polycarbonate and several other advanced polymers. These synthetic polymers have improved chemical stability and better resistance to microbial degradation. Membranes have most commonly been produced by a form of phase inversion known as immersion precipitation.11 This process has four main steps ... 

Polysulphone High heat resistance, to 260°C, and mechanical strength, good chemical stability. 

Similar studies were carried out by Nakase, who determined the effect of radiation on some mechanical and thermal properties of the polysulphone film of composite membranes. After a complete experimental and microscopic smdy, the author concluded that polysulphone film almost keeps transport properties and stability up to dose values of 2 MGy [2]. 

Temperature stability is important for some applications of SILMs in gas separation, such as capture of CO from coal gasification plants. Ilcovich et al. [25] analysed the stability of a SILM based on [hmim+lfNTfj ] supported on a polysulphone organic membranes in the selective separation of CO from He at high temperature. This membrane was found to be stable up to 125 C, the failure of the membranes above that temperature being attributable to support failure rather than any effect on the ionic liquid. Recently, Myers et al. [32] reported operation of [hmim ][NTfj ] supported on nylon membranes up to 300 C. It was found that permeability in this [hmim [NTfj ] membrane increased with temperature while the selectivity decreased. 

Figure 2. Effect of the amount of methacrylic olygomer on the properties of polysulphone-styrene composite materials (a) tensile strength, (b) heat stability (VST).

These materials, the polymeric sulphones, also come into the category of hexavalent sulphur compounds and are derivatives of sulphonic acids. The photochemistry and the radiation chemistry of these substances have been reviewed in a variety of texts. Thus the radiation chemistry was reviewed in considerable detail in 1988147. Other texts have reviewed photodegradation and photooxidation of polymers in general with some reference to the polysulphones149. It appears that polysulphones have low thermal stability and as a result have failed to undergo commercial utilization149. 

Polysulphones The polysulphone family of polysulphone (PSU) and polyether sulphone (PES) is a TP based on sulphone derivatives, aiming at high heat-stability. PSU originated in the discovery of a method of producing high molecular weight aromatic polyethers. 

Because the thermal stability of polystyrenes and polymethacrylates is limited to 200°C, continuous use of a polymer-supported reactive species tends to be limited to significantly lower temperatures than this (see polymeric sulphonic acids). There is considerable interest in supporting, in particular, alkene oxidation catalysts on polymers and to operate reactions at temperatures above 200°C. To achieve this, novel thermo-oxidatively stable supports are required and some progress has been made in this direction. More details of specific applications will be given later, but supports based on, for example, polyacrylonitrile [50-52], polyamides [53-56], polysulphone [57, 58], polyaniline [59] and polybenzimidazole... 

Polysulphones are polymers which contain recurring sulphone groups (-SO2-) in the main chain. Aliphatic polysulphones, prepared by reaction of sulphur dioxide with olefins, have been known for many years but lack of thermal stability has precluded any commercial utilization. In 1958 the preparation of stable aromatic polysulphones was described [5] and since this time a large number of such polymers has been investigated. However, at the present time, the only aromatic polysulphone to have achieved commercial significance is that prepared from 2,2-bis(4 -hydroxyphenyl)propane (bisphenol A) and 4,4 -dichlorodiphenyl sulphone. Only this polysulphone, manufacture of which was started in 1965 by the Union Carbide Corp. (U.S.A.), is described in this chapter. 

While nylon, polycarbonate, modified PPO and particularly ABS continue to have wide application, polyesters are finding increasing favour where heat and solvent resistances and mouldability to fine tolerances are required. Polysulphones have little application and newer materials such as PPS and polyether-ether ketone may find a place in special applications where the requirement for stability, and heat and solvent resistances justifies their high cost. 

High temperature thermoplastics such as polysulphones and polyetherimides are newcomers to the printed wiring substrate arena and offer the potential for the production of relatively low-cost moulded substrates with excellent electrical characteristics and thermal stability. The low dissipation factors characteristic of these materials have generated considerable interest in their potential for use in... 

Polysulphone Udel P-1700 Hydrolytic stability General electrical Union Carbide... 

Although the amount of thermoplastic polymer used with reinforcement is still small there is an increasing interest in the use of reinforcements with thermoplastic as the matrix to provide improved properties, particularly strength, stiffness, dimensional stability, shrinkage and heat resistance. Virtually all thermoplastics have been reinforced and a great many are now available commercially. The best known is nylon but it is expected that great advances will be made in the use of styrenes, olefins and some of the more specialised polymers, such as polycarbonate and polysulphone. 

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