Polyethers copoly

This kind of NAD, resulting from the reaction of crude or pure MDI with high molecular weight polyether triols, is very efficient in stabilising copoly (ACN - styrene) dispersions or even polystyrene dispersions in polyether polyols. 

The polymer polyols of low solid content are obtained by dilution of high solid content polyether polyols with ungrafted polyether polyol (the same polyol used for radical polymerisation). At the same solid content, the polymer polyols obtained by dilution of high solid content polymer polyols with ungrafted polyethers, always have a lower viscosity than the polymer polyols obtained by direct synthesis. Thus, a polymer polyol having 20% copoly (ACN - styrene) obtained by direct synthesis, has a higher viscosity... 

Usually the viscosity of PHD polymer polyols is higher than the viscosity of graft polyether polyols, at the same solids content. For example a graft polyether polyol, with a 20% solid fraction (copoly[ACN - styrene]), has a viscosity of 2000-3000 MPa-s at 25 °C, but a PHD polyol, with the same solids concentration has a viscosity of 3000-3500 MPa-s at 25 °C [10, 67-69]. This high viscosity is direct evidence of the intensive interaction, by secondary forces, between the polyurea filler and the continuous liquid polyether phase. 

Usually an equimolecular mixture diamine, TDI is used (a very small excess of TDI is frequently used to compensate for the consumption of TDI in reaction with hydroxyl groups), which normally leads to maximum molecular weight in the resultant polyurea. As a general observation, the molecular weight of solid polyurea from PHD polyols has a lower molecular weight than the copoly [ACN - styrene] obtained as filler in graft polyether polyols. 

Commercial copoly(ether-ester) elastomers (e.g., Hytrel , DuPont Lomod , GEC) are segmented block copolymers containing a polyether soft segment such as poly(tetramethylene oxide) and a hard segment that is chemically identical to polybutylene terephthalate. When the soft segment is > 50%, these block copolymers exhibit... 

Determined by gpc, using polyethyleneglycol/polyeth eneoxide standards. Calculated on the basis of the mol ular weights of the activated copoly]i (M =8,730, Mi 57,000). Preliminary M, data obtained by sedimottation equilibrium arc cimastent with, but lower than, the theoretical values... 

Wegner, G., et ai, Structure and properties of segmented polyether-esters. II. Crystallization behavior of polyether-esters with random distribution of hard segment length. Die Angewandte Makromolekulare Chemie, 74(1) p. 295.1978. Litvinov, V.M., et ai, Phase Composition of Block Copoly(ether ester) Thermoplastic Elastomers Studied by Solid-State NMR Techniques. Macromolecules, 36(20) p. 7598.2003. 

The polycondensation of o ,ta-diacid (or diester) polyamides with 0 ,aMiihyd-roxy polyethers leads to thermoplastic elastomers with well defined structures and valuable properties. For instance, the polycondensation of a,ta-dicarboxylic polydodecanamides with different a,a -dihydroxy (polyoxyethylene-6-poly-oxypropylenes) led to polydodecanamide-6-copoly ethers [4,5] (Scheme 2),... 

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