Prepolymers, polyether

As will be discussed later, flexible polyester foams are not altogether satisfactory for upholstery applications and in the 1950s the attention of American chemists turned to the use of polyethers. These materials could be obtained more cheaply than the polyesters but the products were less reactive and with the catalyst 

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Reaction Injection Molding. RIM uses the anionic polymeri2ation of nylon-6 to carry out polymeri2ation in the mold. A commercial process involves the production of block copolymers of nylon-6 and a polyether by mixing molten caprolactam, catalyst, and polyether prepolymer, and reacting in a mold (27,28). 

Rigid polyurethane foams can be made from either polyester or polyether prepolymers, which are crosslinked with polyfunctional isocyanates. The resulting foams are largely closed cell, with only about 5 to 10% of cells being open. Rigid polyurethane foams are widely used as insulation in commercial, residential, and industrial settings. 

The addition of plasticizer disrupts the hydrogen bonding in the system and, hence, the physical properties decrease. To overcome this, at low harnesses, some long-chained material can also be added. A simple system is shown in Figure 5.3, where some additional plasticizer such as DIOP is added to a 95 Shore A polyether prepolymer, which has been cured with Ethacure 300. 

The segmented polyamide elastomers are synthesized from MDI (4,4 -diisocyanato-diphenylmethane) and dicarboxylic acids and a carboxylic acid terminated aliphatic polyester, polycarbonate or polyether prepolymer with an average molecular weight of M = 500-5000. The dicarboxylic acids used as hard segment extenders are adipic and azelaic acid. Also, poly(ester amide) alloys are obtained using nylon-6,6 or polyesters (PEA/PBT). 

TDl polyether prepolymers (addition products of TDl and di- or higher functional polyether polyols)... 

Viscosity measurements at constant temperature were made using a conventional Shirley—Ferranti cone-and-plate viscometer. In some cases complications arose due to phase inversion or to the fracture of low-molecular-weight polymer. One case was a typical one-shot flexible polyether foam system. On the other hand, a polyether prepolymer prepared from 2000 M.W. poly(oxypropylene)glycol and 80 20-TDI, reacted with water, formed a homogeneous system initially, and was suitable for study with this technique. The rate of viscosity increase at several temperatures is shown in Fig. 15. 

More recently Dieterich and Reiff (166) have described the formation of aqueous urethane dispersions by the dispersion of ionomer melts with subsequent polycondensation in two-phase systems. The principle of this procedure consists of reacting molten ionic modified polyester or polyether prepolymers containing NCO groups with urea to yield bis(biuret), followed by methylolation by means of aqueous formaldehyde in a homogeneous phase, and the resulting plasticized melt of methylolated ionic urethane bis(biurets) dispersed in water at 50-130 °C. These steps can be represented schematically as follows ... 

VIBRATHANE B 625 is a polyether prepolymer based on polytetramethylene glycol (PTMEG) and MDI raw materials. Based on the 6.5% NCO content, it can be assumed that this was prepared using 1 mole of PTMEG-1000 polyol and 2.2 moles of MDI. It can also be assumed that the HER chain extender produces crystalline hard segments... 

Table 8.3 Cast elastomers based on Uniroyal B-625 (polyether) prepolymer elastomers performance with various HER-TG materials ...

Table 8.11 Cast elastomers based on Baytec ME-050 (polyether) prepolymer. Effect of HER-HQEE composition on elastomer properties ...

Trade mark for Uniroyal TDI/polyether prepolymer. 3,3 -Dichloro-4,4 -diaminodiphenylmethane. 

Anionic surfactants have been used for the preparation of polyester and polyether prepolymer foams. A variety of types of alkali salts of fatty sulphonates or salts of fatty acid or sulphonic acids with amines is described in the patent literature very few references exist for the use of cationic surfactants. 

TDI polyether prepolymers such as the Adiprene LlOO series are viscous liquids at room temperature with a slight isocyanate odour. They are stable at room temperature in the absence of moisture but at elevated temperatures, even when moisture-free, they have only a limited life. A brief description of these prepolymers is given in Table 5.1. 

PU-1. This polyether prepolymer (NCO/OH = 2) was prepared at 80°C under nitrogen. 1.5 equivalent weights of poly (tetramethylene glycol), MW = 661 (PM 660), were slowly added with stirring to three equivalent weights of tolylene diisocyanate (TDI) in a resin kettle. The reaction was allowed to proceed until the theoretical isocyanate content (determined by the di-n-butylamine method) was reached (2 hr). An equivalent weight of a... 

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