Cure speed amine

Advantages of the hydrosilation system (Fig. 3) include the elimination of solvent, improved cure speed, and potential for UV or thermal cure. Drawbacks to the system include more expensive multiroll coating methods, potential poisoning of the Pt catalyst (with Sn, S, Cr, amines, etc.), poor anchorage to some films, and a need to carefully balance the hydride to vinyl ratio employed for cure to avoid detrimental interactions with acid containing adhesives [23,53]. 

One of the means used to modify monomers and polyester acrylates further is to amine modify them. This is normally done using a Michael addition reaction between the acrylate and an amine. The benefits of amine modification are normally seen with increased cure speed since this will tend to overcome the effects of oxygen inhibition in the cure process. Amine oligomers and synergists can also be low viscosity and give improved flexibility to a film. One disadvantage of these materials maybe that perhaps they do not possess the stability required of UV inkjet ink formulations. They are also very prone to yellowing and are unstable with some forms of adhesion promoters. 

Accelerator. A large number of chemical accelerators have been developed which can catalyze the anaerobic cure and reduce the large differences in cure speed on different surfaces. The most commonly used accelerators are saccharin [benzoic sulfimide (II)] and aromatic amines such as A,A-dimethyl-p-toluidine (III) and 1,2,3,4-tetrahydroquinoline (IV). 

One-part urethane adhesives have been used for many years as high performance sealants. In this capacity they provide a useful combination of strength, flexibility, and elastic recovery. As adhesives, these systems have limited use im-less formulated to overcome their inherent disadvantages. One-part polyurethane adhesives are typically moisture-cured and rely on a multistep reaction sequence as follows isocyanate reacts with water to form carbamic acid, the unstable car-bamic acid loses carbon dioxide and generates an amine, the amine reacts with additional isocyanate to form a urea, and the urea reacts with additional isocyanate to form a biuret, which includes a cross-link. Unless it diffuses out of the system, the CO2 can cause foaming. Formulators learn to minimize the isocyanate content (%NCO) of a system in order to balance cure speed with foam control. Cure speeds—and foaming rates—of these systems decrease from the outside in and vary with the amount of atmospheric moisture in the air, which changes hourly and seasonally. 

The resin exhibits a low viscosity, 2500-5000 MPa-s (= cP) at 25°C, and an EEW of 105-114 a moleculariy distilled version (0510) has a viscosity of 550-850 MPa-s (= cP) at 25°C and an EEW of 95-107. It is considerably more reactive toward amines than standard bisphenol A resins. The trifiinctional resin permits curing at low temperatures, ie, 70° C, and rapidly develops excellent elevated-temperature properties. Used as additives to increase cure speed, heat resistance, and Tg of bisphenol A epoxy resins, it has utility in such diverse applications as high temperatures adhesives, tooling compoimds, and laminating systems. 

Isophorone diamine (IPDA), bis(4-aminocyclohexyl)methane (PACM), and 1,2-diaminocyclohexane (1,2-DACH) are the principal commercial cycloaliphatic polyamine curing agents. IPDA is the largest volume cycloaliphatic amine. Commercial cycloaliphatic amines are formulated products. In addition to the cycloaliphatic amines, other components such as aliphatic amines and plasticizers are also included to improve RT cure speed and end-use properties. One popular formulation consists of IPDA used in combination with trimethylhexamethylene-diamines (TMDA) or meta-xylenediamine (MXDA), and plasticizers/accelerators such as nonyl phenol or benzyl alcohol. In some ambient cin-e coating applications, cycloaliphatic amines can be reacted with phenol and formaldehyde to form the Mannich base products, which have an internal phenol accelerator and cure readily at ambient temperatin-es. 

Acrylics such as 1,6-hexanediol diacrylate and trimethylolpropane triacrylate are nonepoxy multifiinctional diluents, which react readily with primary and secondary amines by means of Michael addition of the the amine to the acrylic double bond (190). They have been used to increase cure speed or to lower cure temperature of epoxy-amine systems. Caprolactone acrylates have also been used for this application (191). 

CD-9052 is a trifunctional acid ester adhesion promoter for UV/EB inks emd coatings that offers exceptional cure speed. CO-9052 assists adhesion to difficult stibstrates, such as plastics, metals, and glass. CD-9052 is not recommended for use in formulations containing tertiary amines. Usage levels of 3-12% are recommended. 

Acrylic monomers are used as reactive diluents in amine cure epoxy formulations to reduce viscosity and to increase cure speed. 

The cure speed and adhesion of an anaerobic sealant can be increased by treatment of the surface with a solution of a primer or activator. Early anaerobic thread lockers were strongly affected by part cleanhness, and degreasing the parts with a chlorinated solvent improved performance dramatically. The condensation product of an aldehyde and a primary or secondary amine, a sulfur-containing radical accelerator, or a compound of an oxidizable transition metal were some of the materials used to activate the anaerobic cure [182] - [184]. Due to the ozone-depleting potential of chlorinated solvents, acetone, alcohols, or hydrocarbon solvents are generally used at present. 

Crosslinkers and Accelerators. Besides the polymers themselves, changes and improvements are taking place in curing agents, hardeners, catalysts, and polymer modifiers. For example, if epoxy adhesives with improved heat resistance are needed, the hardeners can be aromatic anhydrides and amines such as benzophenone tetracarboxylic dianhydride, py-romellitic dianhydride, diaminodiphenyl sul-fone. To enhance curing speed, epoxy systems utilize mercaptan hardeners, while acrylic monomer/polymer blends avail themselves of amine/aldehyde catalysts with benzosulfimide (saccharin) accelerators. Radiation-curing systems for today and tomorrow utilize both visible light and laser beams. 

Thus the performance of epoxy resin-polyamine systems with respect to pot-life, flexibility, curing speed, toxicity and the exotherm depends largely on the type of polyamine and the accelerator used. Most of the amine-cured coating systems are designed for room-temperature curing and are sold as two-package systems. 

Other Accelerators. Amine isophthalate and thiazolidine thione, which are used as alternatives to thioureas for cross-linking polychloroprene (Neoprene) and other chlorine-containing polymers, are also used as accelerators. A few free amines are used as accelerators of sulfur vulcanization these have high molecular weight to minimize volatility and workplace exposure. Several amines and amine salts are used to speed up the dimercapto thiadiazole cure of chlorinated polyethylene and polyacrylates. Phosphonium salts are used as accelerators for the bisphenol cure of fluorocarbon mbbers. 

Consist of a range of chemicals which promote cross-linking can initiate cure by catalysing ( catalysts , hardeners, initiators), speed up and control cure (activators, promoters) or perform the opposite function (inhibitors) producing thermosetting compounds and specialised thermoplastics (e.g. peroxides in polyesters, or amines in epoxy formulations). The right choice of a cure system is dependent on process, process temperature, application and type of resin. 

Phenolic-isocyanates (phenolic-urethanes). The binder is supplied in three parts a phenolic resin in an organic solvent (0.8%), methylene diphenyl diisocyanate (MDI) (0.5%), and a liquid amine catalyst. When mixed with sand, the amine causes a reaction between the resin and the MDI, forming urethane bonds, which rapidly set the mixture. The speed of setting is controlled by the type of catalyst. The optimum cure temperature is 25 to 30°C. Compression strength is typically over 4000kPa (600psi). 

Isocyanates and amines react together to form ureas. Primary aliphatic amines react very quickly at temperatures down to ambient, whereas secondary aliphatic and primary aromatic amines react less quickly. The reaction rate of secondary aromatic amines is the slowest. The speed of the reaction can further be modified by the addition of substitutes near the amine group. The control of the speed can either be electronic, as illustrated by the effect of the chlorine in the MOCA ring, or by stereo chemical influences where the groups next to the amine group have a very strong hindrance to the curing. This is... 

The reactivity of the epoxy-anhydride reaction is slow therefore, an accelerator is often used at 0.5 to 3 percent to speed the gel time and cure. Most often the accelerator is a tertiary amine, and the optimum concentration is dependent on the anhydride, the resin used, and the cure conditions. The accelerator concentration, like the anhydride concentration, is usually determined experimentally based on a specific set of end properties. 

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