Polyether polyurethane, commercial

Multiblock copolymers are synthesized by step polymerization using prepolymers containing specific end-groups (Eq. 14). Polyester- and polyether-polyurethanes and polyether-polyesters are multiblock copolymers of commercial interest. Step polymerizations has advantages over living polymerization. There is a... 

Figure 1 shows stress-strain curves for the commercial polyether polyurethane and for PU-13, made from methane diphenyl dllsocyanate (MDI), butane diol (BD), and polytetramethylene oxide diol of molecular weight, 2000 (PTMO 2000). There is little difference in stress values for aged and imaged polymers. 

Figure 1. Stress vs. strain at 25° and 60°C for polyether polyurethanes filled symbols at 25°C unfilled symbols 60°C. Commercial polymer (, 0),unaged ( > A),aged wet. PU13 (9,0),unaged (, ) aged wet.

The types of polymers in current use are somewhat limited and are mainly poly(dimethyIsiloxane), polyethylene, polytetrafluo-roethylene, poly(methyl methacrylate) and derivatives, poly(ethylene terephthalate), poly(vinyl chloride) [plasticized] and some polyether polyurethane ureas. A large number of other polymers are being studied experimentally. Because of the wide diversity of uses, each of which has very specific requirements, it is not possible for any single polymer to be the only material used in medical applications. In the past, medical applications were usually attempted with a commercial grade of a polymer, but this... 

All types of conventional non-ionic surfactants have at one time or another been recommended for use in polyester and, in certain instances, in polyether polyurethanes. However, the predominant surfactants used today are the silicones. These materials are block or graft copolymers or polydimethyl siloxanes and polyalkylene oxides. The polyether part is usually a copolymer of propylene and ethylene oxides. Variations in the commercially available surfactants are in the molecular weight and the weight ratio of the two blocks, the ratio of ethylene oxide to propylene oxide in the polyether portion, and the type of link between the silicone and... 

HYDROLYSIS RESISTANCE OF A TYPICAL COMMERCIAL POLYETHER POLYURETHANE... 

Thermooxidative degradation, which is more of a problem with polyether polyurethanes, can be inhibited by the addition of antioxidants. Mathur et al. have studied the effectiveness of several commercial antioxidants for stabilizing polyether polyurethanes against UV and thermally induced oxidation. Stabilizers against thermooxidation include hindered phenols, aromatic amines, and phosphites. Commercially available antioxidants have recently been reviewed by Allbee. Replacement of some, or all, of the ether linkages in polyether polyurethanes by silicone has led to a marked improvement in the thermooxidative stability of the resulting polymer. " ... 

Foams prepared from phenol—formaldehyde and urea—formaldehyde resins are the only commercial foams that are significantly affected by water (22). Polyurethane foams exhibit a deterioration of properties when subjected to a combination of light, moisture, and heat aging polyester-based foam shows much less hydrolytic stabUity than polyether-based foam (50,199). 

The polymerization of tetrahydrofuran was first studied ia the late 1930s (3,4). In 1960, this work was summarized (4), and the Hterature on tetrahydrofuran polymers and polymerization has been growing ever siace. Polytetrahydrofuran with hydroxy end groups has become a large-scale commercial product, used mainly as the flexible polyether segment ia elastomeric polyurethanes and polyesters. It is commercially available under the trade names Terathane (Du Pont), Polymeg (QO Chemicals), and PolyTHF (BASF). Comprehensive review articles and monographs have been pubUshed (2,5-8). 

Polyurethane foams may be rigid, semi-rigid or flexible. They may be made from polyesters, polyethers or natural polyols such as castor oil (which contains approximately three hydroxyl groups in each molecule). Three general processes are available known as one-shot, prepolymer or quasi-prepolymer processes. These variations lead to 27 basic types of product or process, all of which have been used commercially. This section deals only with flexible foams (which are made only from polyesters and polyethers). Since prepolymers and... 

Although the name polyurethane might be taken as implying that these materials contain urethane groups (—NHCOO—) in the backbone of the macromolecule, for those polyurethanes in major commercial use this is not tme. For such materials the initial macromolecule tends to be a polyester or polyether it is the crosslinks that involve the formation of a polyurethane stmcture. 

The polyether-based polyurethanes are now of greater commercial importance then those based on polyesters. A frequently used polyether is that derived from propene oxide, as illustrated in Reaction 4.9. 

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. 

Polyethers produced via the ROP of epoxides have many commercial uses, and are especially important as precursors to polyurethanes (Scheme 20).927-929 Although a wide variety of reagents can effect the cationic or anionic ROP of epoxides, low molecular weight polyols are generally prepared using potassium or sodium hydroxide.930,931... 

Polymerization of the oxiranes is typically propagated from a starter molecule that is chosen to define the functionality if) of the final polyol. The functionality and the molecular weight of polyols are the main design features that define the polyurethane properties in the end-use applications. Additionally, the balance of EO and PO in the polyether polyols, mainly for flexible foam polyols, is tailored to enhance the compatibility of formulations and the processability of the foam products. The exact composition of the polyols defines the crucial performance features of the final polyurethane product. Even seemingly small differences in polyol composition can result in changes to polyol processabihty and polyurethane performance. This becomes a crucial issue when replacing conventional petrochemical polyols with polyols from different feedstocks. To demonstrate the sensitivity of commercial formulations to changes in feedstocks, a simple example is offered below. 

While the use of these polyethers is widespread, the goal of discussion is to create a specialty chemical. Propylene- and ethylene-based polyols are produced for physical reasons and will serve as the backbone. Researchers should note, however, that the scope of polyethers and polyesters is much broader when they are willing to sacrifice some physical strength to gain a chemical advantage. To illustrate, we cite a particularly interesting example. Castor oil was a conunon polyol for the production of polyurethanes. It was replaced by less expensive and more predictable polyols in commercial production. Readers should be aware that mixed polyols can be used to advantage. 

A polyurethane is fonned by reacting a hydroxyl-terminated polyether or polyester with an isocyanate. An example in commercial practice is the reaction of toluene diisocyanate and polypropylene glycol (PPG) to produce one of the most common forms of polyurethane (see Figure 2.6). 

In 1952, castable polyurethanes first became commercially available. In 1956, the first polyethers were introduced by DuPont, followed by cheaper polyethers... 

Polyurethanes are thermoset polymers formed from di-isocyanates and poly functional compounds containing numerous hydroxy-groups. Typically the starting materials are themselves polymeric, but comprise relatively few monomer units in the molecule. Low relative molar mass species of this kind are known generally as oligomers. Typical oligomers for the preparation of polyurethanes are polyesters and polyethers. These are usually prepared to include a small proportion of monomeric trifunctional hydroxy compounds, such as trimethylolpropane, in the backbone, so that they contain pendant hydroxyls which act as the sites of crosslinking. A number of different diisocyanates are used commercially typical examples are shown in Table 1.2. 

Oligomeric carbodiimides are efficient stabilizers for polyester, polyester based polyurethanes, polyether based polyurethanes and polyether based poly(urethane ureas). Oligomeric carbodiimides are commercially available under the trade name Stabaxol from Rhein Chemie, a subsidiary of Bayer. 

M. Ravey and E. M. Pearce, Elexible polyurethane foam. 1. Thermal decomposition of a polyether-based, water-blown commercial type of flexible polyurethane foam, J. Appl. Polym. Sci., 63, 47-74 (1997). 

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