Curing isocyanates

Isocyanate curing These are used when the ambient temperatures are low because they cure rapidly and at temperatures below 5°C. There is a tendency for such films to become brittle with age, and it is preferable not to use such materials at high ambient temperatures, since the pot life and other properties may become unacceptably short. 

Also in an invention of Frankel et al (Ref 40), a castable expl has been developed which, typically, consists of a polyester binder (20%) such as 3-(2,2,-dinitro-2f-fluoroethyl)-l,2-pro-panediol reacted with an isocyanate curing agent plus HMX (80%)... 

NR can be crosslinked by the use of sulphur, sulphur donor systems, peroxides, isocyanate cures and radiation, although the use of sulphur is the most common method. 

Isocyanate-based resins, in paper manufacture, 13 116 Isocyanate curing agents, 10 410 Isocyanate group, urethanes and, 22 36 Isocyanates... 

Uncured poly(GlyN) prepolymer exhibits good chemical stability and has a satisfactory shelf-life. However, the ageing characteristics of isocyanates cured PU rubbers are unsatisfactory contrary to (NiMMO) rubbers which have good ageing characteristics. Long term ageing trials have shown that the cured... 

Ducote, M.E. (1986) Prevention of unwanted cure catalysis in isocyanate cured binders. US Patent 4,597,811. 

Propellants include both rocket and gun propellants. Most rocket propellants are either Hazard Class 1.3 composites, which are based on a rubber binder, and ammonium perchlorate (AP) oxidizer, and a powdered aluminum (Al) fuel or Hazard Class 1.1 composites, which are based on a nitrate ester, usually nitroglycerine (NG), nitrocellulose (NC), HMX, AP, or polymer-bound NC. If a binder is used, it usually is an isocyanate-cured polyester or polyether. Some propellants contain combustion modifiers, such as lead oxide. 

Epoxies, isocyanate cured polyester, and cyanoacrylates are used to bond acetal copolymer. Generally, the surface is treated with sulfuric-chromic acid. Epoxies have shown 150- to 500-psi shear strength on sanded surfaces and 500- to 1000-psi on chemically treated surfaces. Two-component epoxies give slightly lower bond strengths. However, they bond acetal to itself and to many other materials. 

Commonly used adhesives for both PET and PBT substrates are isocyanate cured polyesters, epoxies, and urethanes. Surface treatments recommended specifically for PBT include mechanical abrasion and solvent cleaning with toluene. Gas plasma surface treatments and chemical etch have been used where maximum strength is necessary. 

The clear-coat is referred to as a two-component (2K) clear-coat when isocyanate is used as the cross-linker. The isocyanate must be added to the hydroxy functional acrylic just prior to spray application to prevent premature cross-linking (or gelation). For this reason, the two-part mixing is referred to as 2K. Cure conditions for isocyanate-cured clear-coat range from room temperature (car refinish) to 250°F for 30 min. 

Pitch-polyurethane coatings are two-component materials containing polyol as the base resin and an isocyanate curing agent. They cure satisfactorily at temperatures as low as 0°C (BSC, undated). 

Maleic anhydride (72) when mixed with triphenylbismuthine in a ratio ranging from 1 1 to 1 1.5 provided a curing catalyst for a propellant composite comprising an oxidizer, isocyanate curing agent, and a hydroxy-terminated polymer binder. The resulting composite showed improved modulus and/or stress values for use with propellants <91 Ml 208-06). 

Hydroxybenzamines of the general formula have been claimed to improve the adhesion of a wide range of coatings to zinc and cadmium and other metallic substrates when used as either pretreatment primers or additives [63]. Ethylenically unsaturated hydroxy-functional amines have been claimed to improve the adhesion of water-based systems [64], and amines have been examined as adhesion promoters for aromatic isocyanate cured adhesives on glass and other substrates [65]. Primary aliphatic amines are claimed to improve the bondability of polyolefines [66] and an oxyethylated polyethylene... 

Table 1 Conservative Estimates of Water Consumption Through Isocyanate Cure During Conventional Hotpressing... 

Foundry core binders are isocyanate-cured alkyd or phenolic adhesives used as binders for sand used to produce foundry sand molds. These sand molds are used to east iron and steel parts. A fast, economical cure of the sand mold is required under ambient conditions. 

Adhesives used to bond acetal homopolymer to itself and to other materials, such as aluminum, steel, natural rubber, neoprene rubber, and Buna rubber, include polyester with isocyanate curing agent, rubber-based adhesives, phenolics, epoxies, modified epoxies, and vinyls. Solvent cementing... 

Other adhesives recommended hy ICI are 3M Company s Scotch Weld 2216 two-part epoxy, Amicon s Uniset A-359 one-part aluminum-filled epoxy, American Cyanamid s BR-89 one-part epoxy, Bostik s 7026 synthetic ruhher and 598-45 two-part adhesive, GE s Silgrip SR-573, and Goodyear s Vitel polyester with isocyanate curing agent. 

Adhesives commonly used are epoxies, urethanes, isocyanate cured polyesters, nitrile-phenolic, and cyanoacrylate. Only cleaning is required prior to applying the adhesive. A recommended surface cleaner is isopropyl alcohol. Cellulosic plastics may contain plasticizers. The extent of plasticizer migration and the compatibility with the adhesive must be... 

Polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) parts are generally joined by adhesives. Surface treatments recommended specifically for PBT include abrasion and solvent cleaning with toluene. Gas plasma surface treatments and chemical etch have been used where maximum strength is necessary. Solvent cleaning of PET surfaces is recommended. The linear film of polyethylene terephthalate (Mylar ) surface can be pretreated by alkeiline etching or plasma for msiximum adhesion, but often a special treatment is unnecessary. Commonly used adhesives for both PBT and PET substrates are isocyanate-cured polyesters, epoxies, and urethanes. Polyethylene terephthalate cannot be solvent cemented or heat welded. 

There is only one commercial series of isocyanate-cured urethane rubbers, namely the Urepan series of Bayer. Urepan 600 is a polyester derived from diethylene glycol adipic acid and toluene diisocyanate. The ratio of polyester to diisocyanate is such that hydroxyl groups, not isocyanate groups, are situated at the ends of the chains. The chain length is kept... 

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