Polyether-ester thermoplastic rubbers

With the expiry of the basic ICI patents on poly(ethylene terephthalate) there was considerable development in terephthalate polymers in the early 1970s. More than a dozen companies introduced poly(butylene terephthalate) as an engineering plastics material whilst a polyether-ester thermoplastic rubber was introduced by Du Pont as Hytrel. Polyfethylene terephthalate) was also the basis of the glass-filled engineering polymer (Rynite) introduced by Du Pont in the late 1970s. Towards the end of the 1970s poly(ethylene terephthalate) was used for the manufacture of biaxially oriented bottles for beer, colas and other carbonated drinks, and this application has since become of major importance. Similar processes are now used for making wide-neck Jars. 

A typical product has a Mn of about 25 000-30 (KX). Whilst this is low compared with most conventional elastomers, the higher values used with these latter materials arises from the need to minimize the importance of non-loadbearing chain ends, a problem which does not arise in a block copolymer terminated by hard segments. A range of materials has been made available in which the proportion of hard segments is varied from about 33 to 85%. Polymers in which the hard blocks have been modified by the presence of tetramethylene-1,4-cyclohexane dicarboxylate have been supplied by Tennessee Eastman (Lilaonitkul and Cooper, 1977). Polyether-ester thermoplastic rubbers of undisclosed composition have also been supplied by AKU under the trade name Arnitel. 

Closely related to the polyether-ester thermoplastic elastomers are thermoplastic polyurethane elastomers, which consist of polyurethane or urethane terminated polyurea hard blocks, with Tg above normal ambient temperature, separated by soft blocks of polyol, which in the mass are rubbery in nature (see Section 4.11 for more details). The main uses of thermoplastic rubbers (e.g., Estane by Goodrich) are for seals, bushes, convoluted bellows, and bearings. 

Examples of vulcanizable elastomers include natural rubber (NR), styrene butadiene rubber (SBR), butadiene rubber (BR), ethylene-propylene-diene monomer-rubber (EPDM), butyl rubber (HR), polychloroprene or neoprene (CR), epichlorohydrin rubber (ECO), polyacrylate rubber (ACM), millable polyurethane rubber, silicone rubber, and flu-oroelastomers. Examples of thermoplastic elastomers include thermoplastic polyurethane elastomers, styrenic thermoplastic elastomers, polyolefin-based thermoplastic elastomers, thermoplastic polyether-ester (copolyester) elastomers, and thermoplastic elastomers based on polyamides. 

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