Polyether diols characteristics

There is also growing interest in multi-phase systems in which hard phase materials are dispersed in softer polyether diols. Such hard phase materials include polyureas, rigid polyurethanes and urea melamine formaldehyde condensates. Some of these materials yield high-resilience foams with load deflection characteristics claimed to be more satisfactory for cushioning as well as in some cases improving heat resistance and flame retardancy. 

The most important characteristics of industrially produced polyether diols and triols homopolymers of propylene oxide are presented in Tables 4.4 and 4.5. All the polyether PO homopolymers, diols or triols have mostly secondary hydroxyls as terminal groups (94-96 % secondary hydroxyls) (see Figure 4.14). 

Table 4.14 Characteristics of polyether diols, bloc terminal poly[EO] block, with a MW ol k copolymer PO-EO, with 2000 daltons...

AO containing various phenolic moieties were prepared by transesterification in the presence of tetraalkyl titanates. Randomly distributed -active moieties are characteristic of 140 (only the hard polyester segment is given) prepared from dimethyl terephthalate, 1,4-butanediol, poly(tetramethylene oxide)diol and dimethyl 5-(3,5-di-tm-butyl-4-hydroxybenzenepropaneamido)isophthalate [181]. The mentioned polymeric AO was used for stabilization of polyether-polyester elastomers. A partial attachement of tetrakis[methylene 3(3,5-di-tert-butyl-4-hydroxy-phenyl)propionate]methane (3) via transesterification reaction was expected in the synthesis of another polyether-polyester elastomer by [182]. A reversible redox polyester was formed from 2,5-bis(2-hydroxyethyl)hydroquinone and dichlorides of aliphatic dicarboxylic acids [137],... 

The later advent of more powerful catalysts, however, made it possible for straight PPC to be used in the preparation of flexible polyurethane foams (see one-shot processes in Chapter 2) without recourse to the foregoing procedures. Also, today the bulk of the polyethers used are triols rather than diols, since these lead to slightly cross-linked flexible foams with improved load-bearing characteristics. 

Chemistry Polyurethane is produced by the reaction of a polyol with an diisocyanate (or in some instances a polyisocyanate) in the presence of catalysts. The polyols of choice are poly(propylene glycol), block copolymers of ethylene oxide (10-15%) with propylene oxide, or the newer polymer polyols (based on polymers such as polystyrene or styrene-acrylonitrile copolymer). Polyester diols such as polycaprolactone diol can be used in place of the polyether polyol in this reaction. The isocyanate of choice is a mixture of the 2,4 and 2,6 isomers of tolylene di-isocyanate in the ratio of 80 20, generally referred to as 80 20TDI. Other isocyanates such as diphenylmethane di-isocyanate (MDI), hexamethylene di-isocyanate (HMDI), and isophorone di-isocyanate (IPDI) are also used. A tin-based or amine catalyst is used to promote the reaction. Given the wide choice of reactants available, the reaction can yield foams with a range of different mechanical and thermal characteristics. 

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