Prepolymer polyamine

Interfdci l Composite Membra.nes, A method of making asymmetric membranes involving interfacial polymerization was developed in the 1960s. This technique was used to produce reverse osmosis membranes with dramatically improved salt rejections and water fluxes compared to those prepared by the Loeb-Sourirajan process (28). In the interfacial polymerization method, an aqueous solution of a reactive prepolymer, such as polyamine, is first deposited in the pores of a microporous support membrane, typically a polysulfone ultrafUtration membrane. The amine-loaded support is then immersed in a water-immiscible solvent solution containing a reactant, for example, a diacid chloride in hexane. The amine and acid chloride then react at the interface of the two solutions to form a densely cross-linked, extremely thin membrane layer. This preparation method is shown schematically in Figure 15. The first membrane made was based on polyethylenimine cross-linked with toluene-2,4-diisocyanate (28). The process was later refined at FilmTec Corporation (29,30) and at UOP (31) in the United States, and at Nitto (32) in Japan. 

Polyurethane adhesives are known for excellent adhesion, flexibihty, toughness, high cohesive strength, and fast cure rates. Polyurethane adhesives rely on the curing of multifunctional isocyanate-terrninated prepolymers with moisture or on the reaction with the substrate, eg, wood and ceUulosic fibers. Two-component adhesives consist of an isocyanate prepolymer, which is cured with low equivalent weight diols, polyols, diamines, or polyamines. Such systems can be used neat or as solution. The two components are kept separately before apphcation. Two-component polyurethane systems are also used as hot-melt adhesives. 

When you buy epoxy glues, they come in two parts the resin (prepolymer) and the hardener. The hardener can be any of a wide variety of compounds having basic or nucleophilic properties. Polyamines are the most common hardeners. The hardener can attack a terminal epoxide group, initiating a polymerization of the chain ends. 

Separately, Gu et al. [46] reported the use of lipases to facilitate the synthesis of a family of polyaminoamides. The polyaminoamides were made by a two-step reaction, where the first step was Michael addition of 1 mole of a polyamine and 2 moles of an acrylic compound to form an amine-containing diester, and the second step was the polymerization of additional polyamine with the resulting diester prepolymer at 70-140 °C or in the presence of an enzyme at 60-80 °C. 

Two-Package Coatings Isocyanate-Terminated Prepolymers Cured with Polyamines... 

Two-component adhesives typically consist of low-equivalent-weight isocyanate or prepolymer that is cured with a low-equivalent-weight polyol or polyamine. They may be 100% solids or solvent borne. Since the two components will cure rapidly when mixed, they must be kept separate until just before application. Application is followed quickly by mating of the two substrates to be bonded. 

After addition of prepolymer-ionomer and crosslinking it with polyamine some of these particles may remain untouched, but both new hybrid core-shell particles where acrylic/ styrene polymer will constitute the core and polyurethane-urea will form the shell ... 

Figure 6.34 Schematically presented embedded sphere morphology of the particles of hybrid dispersions prepared according to method 2 (diluting the prepolymer-ionomer with monomers, emulsifying it in water, crosslinking with polyamine and polymerisation)...

The polyether-ester polyamic acid imidization process in a solid state under microwave irradiation was studied by Yu et al. [73]. The prepolymer, polyether-ester polyamic acid, was prepared by the polycondensation of poly(tetramethylene ether)glycol di-p-aminobenzoate (Polyamine-650, Polaroid, Co.) and pyromellitic acid dianhydride (PMDA) at room temperature in DMF solution. Later, the prepolymer solution was cast on polytetrafiuoroethylene plates to form 200 pm thin films that were imidized under microwave irradiation in a household microwave oven at 60 °C. The temperature was measured by means of a thermocouple applied to the film surface immediately after the intervals of microwave turn off It was found that microwave irradiation reduced both the reaction temperature and time. For example, during the solid phase thermal polymerization 68.3% polyamic acid was converted to polyimide at 155 °C, while under microwave irradiation 65 % of polyamic acid was reacted at 60 °C within 3 h [73]. 

One component of a two-part urethane adhesive typically contains an NCO-terminated prepolymer and possibly fillers. The second component consists of polyfunctional, NCO-reactive materials, such as polyols and/or polyamines, and may also contain fillers and catalysts. The work life and rate of cure can be adjusted by the selection of catalysts, the catalyst level, and the starting materials used to prepare the resins. Table III lists the cure times for three adhesives which have identical bond strengths when cured, but different work lives. Two-part urethane systems usually cure at room temperature, but the cure can be accelerated by the use of heat. Although... 

The evolved CO2 can lead to a highly cross-linked foam which is soft or hard depending on the prepolymers used. Similarly, the hardness of the set adhesive is determined by the hydrocarbon chain length in the polyol or polyamine used to react with the diisocyanate. Cross-linking by short-chain triols leads to a hard adhesive, whereas long diols result in elastomeric material, often used in textiles, or where a flexible joint is required. 

These prepolymers, which have been called ethoxylenes, are now called epoxy resins. Castan [41 crosslinked these polyethers by heating them with phthalic anhydride. Dicyanodiamide and ditolylguanidine were also used as crosslinking agents, and patents were granted for the use of amines and reaction products of dimerized fatty acids and aliphatic polyamines (Versamids) [5]. 

Chemically reactive polyurethanes include both one- and two-component systems. One-component systems are usually based on a polyether polyol treated with a polyisocyanate to give an isocyanate-terminated polymer. A one-component system cures when exposed to moisture at room temperature. One-component polyurethane hot-melt adhesives are also cured by moisture after application. Two-component systems result from the reaction of low molecular mass polyols and isocyanates or from isocyanate-terminated prepolymers with either polyols or polyamines. Two-component systems cure at room and/or elevated temperatures. 

Prepolymers with terminai isocyanate groups can react with and are hardened both with amino or hydroxyl compounds and with water. Hardening with water is preferred for one-pack systems, for which both atmospheric moisture and the film of water on the substrates act as hardeners for the prepolymer. Cross-linking with polyamines is particularly fast compared with curing by polyols. 

Ethyoxyline resins, now called epoxy resins, were patented by Schlack in 1939. Many of the prepolymers were versatile resins produced from the condensation of a diphenol (bisphenol A) and epichlorohydrin. Since these resins possess terminal oxirane (epoxy) groups, they can be crosslinked in reactions with polyamines at ordinary temperatures. These resins may also be crosslinked by esterifying the pendant hydroxyl groups by cyclic anydrides at elevated temperatures. 

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