Polyurethane one-component

Polyurethane systems are also formulated for surface-coating applications. A wide range of such products has become available. These include simple simple solutions of finished polymer (linear polyurethanes), One component systems containing blocked isocyanates, two-component systems based on polyester and isocyanate or polyether and isocyanate, and a variety of prepolymer and adduct systems. 

PROPENE The major use of propene is in the produc tion of polypropylene Two other propene derived organic chemicals acrylonitrile and propylene oxide are also starting materials for polymer synthesis Acrylonitrile is used to make acrylic fibers (see Table 6 5) and propylene oxide is one component in the preparation of polyurethane polymers Cumene itself has no direct uses but rather serves as the starting material in a process that yields two valuable indus trial chemicals acetone and phenol... 

Neopentyl alcohol is useful for preparation of masked polyol siUcate esters, capable of releasing the polyol under moisture conditions, in moisture-curable one-component Hquid polyurethane compositions (90). 

Polyurethane sealant formulations use TDI or MDI prepolymers made from polyether polyols. The sealants contain 30—50% of the prepolymer the remainder consists of pigments, fiUers, plastici2ers, adhesion promoters, and other additives. The curing of the sealant is conducted with atmospheric moisture. One-component windshield sealants utili2e diethyl malonate-blocked MDI prepolymers (46). Several polyurethane hybrid systems, containing epoxies, siUcones, or polysulfide, are also used. 

Metal salts of neodecanoic acid have also been used as catalysts in the preparation of polymers. For example, bismuth, calcium, barium, and 2kconium neodecanoates have been used as catalysts in the formation of polyurethane elastomers (91,92). Magnesium neodecanoate [57453-97-1] is one component of a catalyst system for the preparation of polyolefins (93) vanadium, cobalt, copper, or kon neodecanoates have been used as curing catalysts for conjugated-diene butyl elastomers (94). 

The conventional polyisocyanurate may be prepared with a two-component system using standard polyurethane foaming equipment. It is usual to blend isocyanate and fluorocarbon to form one component whilst the activator or activator mixture form the second component. 

Two-component waterborne urethane dispersions are similar to the one-component PUD s in that a polyurethane dispersion comprises one of the two components. The second component is usually a crosslinker from the following classes of materials (a) polyisocyanates, (b) aziridines, (c) polycarbodiimides, and (d) epoxies. Many of the crosslinkers are not inherently water-soluble or water-dispersible. Therefore, they must be modified with surface active agents themselves, so as to become emulsifiable in water. 

Example 11. One-Component, Moisture-Cure Polyurethane Sealant. This example is of a low-hardness, high-elongation, moisture-curable polyurethane sealant. The material is based on a low-%NCO prepolymer made from 4,4 -MDI and a low-unsaturation (low-monol-content) Acclaim polyol from Bayer. It is adapted from (a) J. Lear et al., Adhesives Age, February 1999, pp. 18-23 and (b) B. Lawrey, et al., presented at UTECH 2000, The Hague, The Netherlands, March 30, 2000, Crain Communications London, 2000. 

One-component (1-K) polyurethane dispersions (PUDs), 206. See also 1 -K products... 

Most polyurethanes are different from other elastomers in that they are cast. Two components are mixed together. One component is a prepolymer which consists of two major chemical structures. One... 

Blends of 10% aminosilane F and 90% hydrophobic silanes, i.e. vinylsilane A, chloropropylsilane B, methylsilane G, and phenylsilane I, gave superior adhesion of three types of polyurethane (RIM, thermoplastic, and one-component rigid) to glass compared with aminosilane F alone. Table 3 shows that the blend with phenylsilane I gave the best adhesion overall to all three polyurethanes after 5 h in boiling water. This improved performance is attributed to the enhanced hydrophobicity of the interphase region which is conferred by the replacement of most of the hydrophilic aminosilane with hydrophobic silane. 

Several poly(urea urethane) oligomers 28 (Figure 12) were prepared by one-component polycondensation of iV-(hydroxyalkyl)-2 -oxo-1,3-diazepane-l-carboxamides, which act as intramolecular blocked isocyanates <2005PLM 1459>. These oligomers are semicrystalline materials and their melting points show the odd/even effect observed earlier for [ ]-polyamides, [ ]-polyurethanes, poly(ester amide)s, and poly (amide urethane)s. Further analysis showed that the polymers are stable up to ca. 205-230 °C, the polymers with the lower number of methylene groups in the amino alcohol decomposing at the lowest temperature. 

Novel, toughened one-component epoxy structural adhesives based on epoxy-terminated polyurethane prepolymer incorporating an oxolidone structure were developed to provide improved toughness, fracture resistance and adhesive properties with good chemical and moisture resistance.21 The hybrid resin cures with a standard latent curing agent/accelerator. 

The major synthetic adhesives used for bonding wood include urea, phenol, and melamine formaldehyde resorcinol formaldehyde, phenol resorcinol, and polyvinyl acetate emulsions. More recently one-component, moisture cured polyurethane adhesives have become popular for bonding wood. Natural adhesives such as casein and animal glues are also often used for general-purpose wood bonding. Epoxies have been used for certain specialized wood joining applications such as when wood is bonded to metal substrates. 

First-generation solventless polyurethane adhesives are one-component isocyanate terminated prepolymers formed by the reaction of MDI (4,4 methylene bis (phenyl isocyanate)), or other isocyanates with polyether and/ or polyester polyols. One-component 100% solids adhesives rely on moisture from the air or substrates or from induced moisture misting during the converting process, to cure the adhesive via an isocyanate/water reaction and subsequent polyurea-polyurethane polymer formation. Typically the high viscosity of the adhesive is such as to require adhesive delivery equipment and application rollers heated from 65-80 °C for use. They have a high level... 

Properties of fibers can be altered by carrying out interfacial polymerizations on their surfaces. Thus the shrink resistance of wool can be improved by immersing the fiber first in a solution containing one component of a condensation polymer and then immersing it in another solution containing theother component. Polyamides, polyurethanes, polyureas, and other polymers and copolymers may be grafted on wool in this manner. 

One-component polyurethane sealants are based on a polyether or polyester isocyanate prepolymer end-capped with a room-temperature-curable group such as trialkoxy silane. Free isocyanate groups are not used in one-part systems because carbon dioxide is evolved on reaction with moisture from the atmosphere which results in bulging of the sealant in the joint. 

Table 4,3 Properties of one-component and two-component polyurethane sealants...

Polyurethane floor toppings are usually one-component moisture-cured materials, applied on concrete floors to prevent dusting. They are applied... 

Figure 4.5 Polyurethane adhesives used in housing components for bonding plywood 4.6.2 One-component adhesives...

Liquid polyurethane waterproofing systems are coal-tar modified products. Two-component materials are catalysed curing systems, and one-component materials are cured by exposure to moisture. Both the materials exhibit comparable properties on complete curing. Two-component materials require on-site mixing of the components. One-component materials can be applied directly, but the problem with this type is polymerisation of the product inside the container if it is improperly sealed. Such products are purged with an inert gas when the pack is sealed. 

Prepolymer A polyurethane reaction intermediate made by reacting isocyanate with a polyester or polyether, in which one component is in considerable excess of the other. 

The water adsorbed on the adherends and present in the ambient air, which is available as a reactant for the moisture-curing one-component polyurethane adhesives (Section 4.2.2). This reaction is also typical for sealing compounds on polyurethane basis (Section 4.9) used, for example, in construction engineering for the sealing of joints between window and door frames and brickwork. 

Figure 4.2 Moisture curing of one-component polyurethane adhesives.

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