Cyanoacrylates low viscosity

Manufacturers Comments Methyl cyanoacrylate. Low viscosity. Fast cure. 

Manufacturers Comments Ethyl cyanoacrylate. Low viscosity. Fast Manufacturers Comments Alkylester cyanoacrylate. Very low ... 

Manufacturers Comments Cyanoacrylate. Medium viscosity. Manufacturers Comments Cyanoacrylate. Low viscosity. No skin ... 

Manufacturers Comments Filled ethyl cyanoacrylate. Very good Manufacturers Comments Isopropyl cyanoacrylate. Low viscosity. ... 

The most commonly used liquid tissue adhesives are cyanoacrylates. Their low viscosity makes their delivery easy through small coaxial microcatheters. However, their rapid polymerization when in contact with blood, can make precise and safe occlusion challenging. Usually they are mixed with an oil-based contrast media, such as Ethiodol (Savage Laboratories, Melville, NY). The contrast serves to both opacify the cyanoacrylate and slows the polymerization time [30]. 

All of the commercial alkyl cyanoacrylate monomers are low-viscosity liquids, and for some applications this can be an advantage. However, there are instances where a viscous liquid or a gel adhesive would be preferred, such as for application to a vertical surface or on porous substrates. A variety of viscosity control agents, depending upon the desired properties, have been added to increase the viscosity of instant adhesives [21]. The materials, which have been utilized, include polymethyl methacrylate, hydrophobic silica, hydrophobic alumina, treated quartz, polyethyl cyanoacrylate, cellulose esters, polycarbonates, and carbon black. For example, the addition of 5-10% of amorphous, non-crystalline, fumed silica to ethyl cyanoacrylate changes the monomer viscosity from a 2-cps liquid to a gelled material [22]. Because of the sensitivity of cyanoacrylate esters to basic materials, some additives require treatment with an acid to prevent premature gelation of the product. 

As with other acrylics, the monomers are liquids of low viscosity that polymerize very easily in the presence of a slightly basic surface containing adsorbed water. Polymerization is ionic. The resulting polymers have different properties, depending on the alkyl group. The methyl ester (methyl-2-cyanoacrylate) is the most commonly used compound. This material is formulated with a thickener (to prevent starved joints from being formed) and a plasticizer to make it more resistant to shock loading. The thickener can be a polymer of the same monomer. An essential feature is a stabilizer to prevent polymerization in the adhesive container, which is usually made of polyethylene. 

Cyanoacrylate adhesives are relatively low viscosity fluids based on acrylic monomers and characterised by extremely fast rates of cure. When placed between closely fitting surfaces, some will cure to give a strong joint in two to three seconds. 

Pure cyanoacrylate monomers are clear, colorless, low-viscosity liquids at room temperature. They typically have pungent odors. Most cyanoacrylate esters are miscible in moderate- to high-polarity solvents, but nucleophilic solvents will cause polymerization. These properties and others are detailed in Table II. 

Gap filling. Cyanoacrylate polymerization is surface catalyzed, which restricts the ability to cure through a thick section. Also, many low-viscosity adhesives readily flow out of a wide bondline. Gaps up to about 0.015 inch can be bridged by employing a viscous adhesive and a mild surface initiator. 

For those products having a low viscosity, less than 30,000 centipoise, it is possible to apply them by means of a pressure pot and some type of valve and nozzle. Pressure vessels for this purpose range from the small devices generally sold for materials such as cyanoacrylates up to paint-type pressure pots of several gallons. Dispensing valves can be manually operated or in some cases electric or air-operated automatic valves can be employed. Air spray guns, both manual and automatic, can sometimes be adapted for this use. A suitable fluid tip size is selected and the gun is used without the atomization air cap or air supply. This provides a convenient, inexpensive flow gun for use with products that do not require fluid pressures above the working pressure of the spray gun. 

Cyanoacrylate monomers are generally low viscosity, colorless liquids that are unstable in the absence of acidic stabilizers. The commercially important materials are lower alkyl esters of 2-cyanoacrylic acid including methyl, ethyl, n-propyl, al-lyl, n-butyl, isobutyl, 2-methoxyethyl, 2-methoxypropyl, and n-octyl derivatives. The structures of some of these monomers are shown in Figure 1. The physical properties of these and related monomers are reported in detail in several previous... 

The cyanoacrylate adhesives are more rigid and less resistant to moisture than acrylate acid diester adhesives. They are available only as low-viscosity liquids that cure in seconds at room temperature without the need of a primer. The cyanoacrylate adhesives bond well to a variety of substrates, as shown in Table 7.25, but have relatively poor thermal resistance. Modifications of the original cyanoacrylate resins have been introduced to provide faster cures, higher strengths with some plastics, and greater thermal resistance. 

Cyanoacrylates are now widely available for domestic use. When first introduced, their low viscosity, together with the unusual phenomenon of an instant adhesive and good adherence to skin, resulted in some users finding themselves stuck to the parts. With public experience and new formulations, this problem has diminished. 

Manufecturers Comments Ethyl Cyanoacrylate. General purpose, low Manufacturers Comments General purpose, low viscosity. ... 

Manufacturers Comments Ethyl ester cyanoacrylate. Solvent liee. Fast cure, high strength (fully cured). Low viscosity. 

Manuiacturers Comments Ethyl cyanoacrylate. Very low viscosity. Manufticturers Comments Ethyl cyanoacrylate. Medium viscosity. ... 

The disadvantages of epoxies include their two-component (or heat-cure) form, reduced performance on oily snrfaces, their inherent lack of toughness, and limited performance on thermoplastics reactive acrylics, cyanoacrylates and polyurethanes are usually superior in such departments. Also, the base resins are relatively high-molecular-weight species, so it is not possible to formulate very-low-viscosity adhesives unless reactive diluents are added, with a corresponding drop in performance. 

Cyanoacrylate One-component, very fast curing, low viscosity, high strength on most plastics Poor gap filling, cannot autoclave, blooming, can stress crack some plastics... 

The lower esters of the alkyl cyanoacrylates cure to clear, hard resins which exhibit good adhesion and tensile shear strengths to a wide variety of substrate combinations. They are, however, brittle and exhibit low peel and impact strengths. Higher viscosity versions of the lower esters filled with 5-10% of poly(methylmethacrylate) resins are somewhat less brittle and can offer double the impact strength of low viscosity monomeric adhesives, as well as significantly better peel strengths. 

The a-alkyl cyanoacrylate super glues ( one drop holds 5000 lbs ) are now a familiar part of the consumer market. Originally, the monomers had extremely low viscosities and so could crawl into narrow crevices and wet the adherend surfaces rapidly. On the other hand, they would not fill gaps and were absorbed into porous adherends, giving poor bonds. Newer versions are available with higher viscosities to overcome these drawbacks. Cyanoacrylates can polymerize in seconds by an anionic addition reaction believed initiated by hydroxyl ions from water adsorbed on the adherend surfaces ... 

The extremely fast cure (seconds to minutes), low viscosity (mPas), and ability to form strong bonds with many substrates, including glass, ceramic, aliuninum, steel, rubber, plastic, wood, and their combinations, make the cyanoacrylates excellent for assembly line bonding. These adhesives have good solvent resistance but show some loss in bond strength on aging in water and in air at temperatures above 212°F (100°C). 

Pinch valves are used for low-viscosity adhesives which are processed in the pressure range up to 10 har (O Fig. 38.9). The tube cross section is pinched in such a way by a pneumatically driven lever that the flow of adhesive is stopped. The advantage is that the actual valve mechanism does not come into contact with the adhesive. This type of valve is the preferred for processing anaerobically curing adhesives and cyanoacrylates. 

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