Polyethers from Glycols and Alkylene Oxides

Controlled polymerisation of ethylene oxide under alkaline conditions will produce a range of polymers marketed under the trade name Carbowax. These have molecular weights in the range 1500-20000 and are greases or waxes according to their degree of polymerisation. Lower molecular weight polymers 

In 1958 the Union Carbide Corporation introduced high molecular weight, highly crystalline ethylene oxide polymers under the trade name Polyox. Although similar in appearance to polyethylene they are miscible with water in all proportions at room temperature. 

Unlike the lower molecular weight poly(ethylene oxide)s these materials are tough and extensible, owing to their high molecular weight and their crystallinity. Typical mechanical properties of the polymer are given in Table 19.5 

The tensile strength will depend to a large extent on the rate of extension and the relative humidity. There is a severe drop in tensile values as the relative humidity exceeds 80%. 

Unlike other water-soluble resins the poly(ethylene oxide)s may be injection moulded, extruded and calendered without difficulty. The viscosity is highly dependent on shear rate and to a lesser extent on temperature. Processing temperatures in the range 90-130°C may be used for polymers with an intrinsic viscosity of about 2.5. (The intrinsic viscosity is used as a measure of molecular weight.) 

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Polyether Polyols. Polyether polyols are addition products derived from cyclic ethers (Table 4). The alkylene oxide polymerisation is usually initiated by alkah hydroxides, especially potassium hydroxide. In the base-catalysed polymerisation of propylene oxide, some rearrangement occurs to give aHyl alcohol. Further reaction of aHyl alcohol with propylene oxide produces a monofunctional alcohol. Therefore, polyether polyols derived from propylene oxide are not truly diftmctional. By using sine hexacyano cobaltate as catalyst, a more diftmctional polyol is obtained (20). Olin has introduced the diftmctional polyether polyols under the trade name POLY-L. Trichlorobutylene oxide-derived polyether polyols are useful as reactive fire retardants. Poly(tetramethylene glycol) (PTMG) is produced in the acid-catalysed homopolymerisation of tetrahydrofuran. Copolymers derived from tetrahydrofuran and ethylene oxide are also produced. 

Poly(alI lene glycol)s. While these can be made from polymeri2ation of any alkylene oxide, they are usually prepared either from propylene oxide as the water-insoluble type, or as water-soluble copolymers of propylene oxide and up to 50% ethylene oxide (35,36) (see Polyethers, propylene OXIDE polymers). Current worldwide production is estimated to be about 45,000 t. 

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