Polyols, urethane foams from

Nonreactive additive flame retardants dominate the flexible urethane foam field. However, auto seating appHcations exist, particularly in Europe, for a reactive polyol for flexible foams, Hoechst-Celanese ExoHt 413, a polyol mixture containing 13% P and 19.5% Cl. The patent beHeved to describe it (114) shows a reaction of ethylene oxide and a prereacted product of tris(2-chloroethyl) phosphate and polyphosphoric acid. An advantage of the reactive flame retardant is avoidance of windshield fogging, which can be caused by vapors from the more volatile additive flame retardants. 

Polyols. Several important polyhydric alcohols or polyols are made from formaldehyde. The principal ones include pentaerythritol, made from acetaldehyde and formaldehyde trimethylolpropane, made from -butyraldehyde and formaldehyde and neopentyl glycol, made from isobutyraldehyde and formaldehyde. These polyols find use in the alkyd resin (qv) and synthetic lubricants markets. Pentaerythritol [115-77-5] is also used to produce rosin/tall oil esters and explosives (pentaerythritol tetranitrate). Trimethylolpropane [77-99-6] is also used in urethane coatings, polyurethane foams, and multiftmctional monomers. Neopentyl glycol [126-30-7] finds use in plastics produced from unsaturated polyester resins and in coatings based on saturated polyesters. 

In the manufacture of highly resident flexible foams and thermoset RIM elastomers, graft or polymer polyols are used. Graft polyols are dispersions of free-radical-polymerized mixtures of acrylonitrile and styrene partially grafted to a polyol. Polymer polyols are available from BASF, Dow, and Union Carbide. In situ polyaddition reaction of isocyanates with amines in a polyol substrate produces PHD (polyhamstoff dispersion) polyols, which are marketed by Bayer (21). In addition, blending of polyether polyols with diethanolamine, followed by reaction with TDI, also affords a urethane/urea dispersion. The polymer or PHD-type polyols increase the load bearing properties and stiffness of flexible foams. Interreactive dispersion polyols are also used in RIM appHcations where elastomers of high modulus, low thermal coefficient of expansion, and improved paintabiUty are needed. 

Over 4 billion PETP bottles will be available for colleetion across Europe in 1999. PUR Products has introduced technology into the UK which involves glycolysis of postconsumer PETP into materials for the manufacture of rigid urethane foams for building insulation. This application offers a substantial new market for aromatic polyester polyols derived from glycolised PETP recyclate. PUR(PRODUCTS)LTD. 

Polyurethane is a condensation polymer generally formed by the reaction between a di-isocyanate and a hydroxylated-terminated resin known as polyol in the presence of a catalyst and a foaming agent The urethane foam formed as a result of this reaction is a cellular polymer that derives its mechanical properties in part from the cell matrix formed during its manufacture and in part from the intrinsic polymer properties. Choice of the di-isocyanate and polyol dictates the inherent polymer properties in addition filler materials may be added to the polymer to improve its mechanical properties. 

Chem. Descrip. Polypropylene glycol polyol Uses Polyol in moisture-cured urethane coatings, filled elastomers improves tensile, tear, and elong. in flexible urethane foams Properties Pt-Co 50 max. dear liq. m.w. 2000 sp.gr. 1.005 (20/20 C) add no. 0.1 max. hyd. no. 54.5-57.5 pour pt. -25 F flash pt. (PMCC) 370 F ref. index 1.4488 pH 6-8 (10 6 IPA/water) 0.03% max. water Storage Store under dry, inert gas blanket such as nitrogen to minimize contamination from contact with air and water... 

Isocyanurate foam n. A foam prepared from an isocyanurate. The unmodified foams have excellent flame resistance but are brittle and of little commercial value. However, isocyanurate foams modified withepoxides, polyimides, or (most commonly) urethane groups and polyols possess flame resistance far superior to that of conventional urethane foams and can be processed into a variety of foam products suitable for insulation. James F (ed) (1993) Whittington s dictionary of plastics. Technomic Publishing Co. Inc., Carley. 

A number of sugar-based polyols (e.g. derived from sucrose, a-methyl glucoside, dextrose, sorbitol, etc.) containing phosphorus in the form of phosphate, phosphite or phosphonate linkages have been reported for use in flame-retardant, rigid urethane foams (52-59). Recent reviews on flame-retardant urethanes incTu3e those of Papa ( 2) and Frisch and Reegen ( 3). 

Polyurethane Foam n (urethane foam, isocyanate foam) This family of foams differs from other cellular plastics in that the chemical reactions causing foaming occur simultaneously with the polymer-forming reactions. As in the case of Polyurethane Resins the polymeric constituent of urethane foams is made by reacting a polyol with an isocyanate. The polyol may be of the polyester or polyether type. When the isocyanate is in excess of the amount that will react with the polyol. 

Efforts are underway to improve superabsorbent polymers used for coolants and water-absorption sheet materials. A water-absorption sheet material made of a polyurethane connected-pore foam from a special polyol and polyisocyanate can be used to disperse superabsorbent polymer powder. This water-absorption sheet has a high rate of water absorption, no volumetric changes, and excellent water-holding ability. Thus, it is ideal for the application of the aforementioned immersing self-absorbing coolant. In the presence of a superabsorbent polymer, urethane reaction takes place to form a polyurethane foam that includes the superabsorbent polymer powder [6]. 

Foam dressings are typically composed of polyurethane, but can also be constructed from rubber, acrylic, polyethylene, neoprene, etc. The value of urethane foams is derived from their well-established biocompatibility. Further to this, by suitable choice of diisocyanate and polyol combination, they can be tailored to be hydrophilic or hydrophobic. The former is useful in exudate reduction, while the latter may have lower adherence to the wound surface. These foams can be impregnated with pharmaceuticals, such as antibiotics, or activated carbon to reduce odor. 

ASTM D2849-69, Standard Methods of Testing Urethane Foam Polyol Raw Materials, describes a number of tests used for analyzing poly(alkylene oxide)s (1). These tests include metals analysis, acid and hydroxyl numbers, unsaturation values, water, suspended matter, specific gravity, viscosity, and color. Many of these tests are well known and will not be described. Those tests dealing with end groups—i.e., the functional groups that are used in the further reaction of poly(alkylene oxide)s—are discussed below. Detailed test procedures can be found in the cited reference and also can be obtained from poly(alkylene oxide) suppliers. 

Basically, flexible polyurethane foams are formed from polyols and isocyanates. The polyols have hydroxyl functionalities of at least 2 if the foam is to be made by a prepolymer process and of 3 or more if the foam is to be made by a "oneshot" process. The prepolymer process proceeds in two distinct steps while in the one-shot process, all reactants are intensively mixed together at the begiiming of the foaming process. Early in the development of urethane foams, the polyols were polyester diols now, however, by far the largest volume of polyols for urethane foams are poly(propylene oxide) polyols or poly(propylene oxide) polyols containing up to 25... 

Foams. Polyurethane foams are prepared by the polymerization of polyols with isocyanates. One of the most commonly used reactive isocyanates toluenediisocyanate, TDI. It is made from toluene by nitration and then reduction followed by treatment with phosgene. The isocyanate residue reacts readily with alcohols to give carbamates (urethanes) or amines to give ureas. 

Thermal degradation of foams is not different from that of the solid polymer, except in that the foam structure imparts superior thermal insulation properties, so that the decomposition of the foam will be slower than that of the solid polymer. Almost every plastic can be produced with a foam structure, but only a few are commercially significant. Of these flexible and rigid polyurethane (PU) foams, those which have urethane links in the polymer chain are the most important. The thermal decomposition products of PU will depend on its composition that can be chemically complex due to the wide range of starting materials and combinations, which can be used to produce them and their required properties. Basically, these involve the reaction between isocyanates, such as toluene 2,4- and 2,6-diisocyanate (TDI) or diphenylmethane 4,3-diisocyanate (MDI), and polyols. If the requirement is for greater heat stability and reduced brittleness, then MDI is favored over TDI. 

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