Amorphous polyarylene sulphides

The Phillips Corporation have recently introduced interesting copolymers related to PPS. In addition to the use of p-dichlorobenzene and Na2S, a second aromatic dichloro compound is used. For the marketed material PAS-2 this is 4,4 -dichlorodiphenylsulphone whilst for the developmental products PAS-1 and PAS-B the compounds are 4,4 -dichlorodiphenyl and 4,4 -dichlorodiphenyl-ketone. Each of these copolymers is amorphous, so that a high heat deformation resistance requires a high value for.  

PAS-2 is particularly notable for its high level of chemical and hydrolysis resistance in addition to a Tg of 215°C. Some typical properties of the copolymers PAS-1 and PAS-2 are given in Table 21.2 in comparison with data for PPS. 

Although it is somewhat of an oversimplification, the polysulphones are best considered as a group of materials similar to the aromatic polycarbonates but which are able to withstand more rigorous conditions of use. Because of their higher price they are only considered when polycarbonates or other cheaper polymers are unsuitable. 

The simplest aromatic polysulphone, poly-(p-phenylene sulphone) (formula I of Table 21.3) does not show thermoplastic behaviour, melting with decomposition above 500°C. Hence in order to obtain a material capable of being processed on conventional equipment the polymer chain is made more flexible by incorporating ether links into the backbone. 

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also introduced a material intermediate between III and V known as Polyethersulphone 720P (IV) but which has now been withdrawn.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. 

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