Cyanoacrylates based adhesives

Interestingly, this same effect has been observed for the addition of a rubber toughening agent to ethyl cyanoacrylate-based adhesives, as was reported previously. The rubber must contain enough latent acid functionality on the polymer backbone or in an additive to inhibit the thermally activated decomposition of the alkyl cyanoacrylate adhesive polymer. 

Low surface energy substrates, such as polyethylene or polypropylene, are generally difficult to bond with adhesives. However, cyanoacrylate-based adhesives can be effectively utilized to bond polyolefins with the use of the proper primer/activa-tor on the surface. Primer materials include tertiary aliphatic and aromatic amines, trialkyl ammonium carboxylate salts, tetraalkyl ammonium salts, phosphines, and organometallic compounds, which are initiators for alkyl cyanoacrylate polymerization [33-36]. The primer is applied as a dilute solution to the polyolefin surface, solvent is allowed to evaporate, and the specimens are assembled with a small amount of the adhesive. With the use of primers, adhesive strength can be so strong that substrate failure occurs during the course of the shear tests, as shown in Fig. 11. 

This difference in reactivity between the different classes of amines explains the difference in the primer performance on polyolefin substrates with ethyl cyanoacrylate-based adhesives [37J. Since primary and secondary amines form low molecular weight species, a weak boundary layer would form first, instead of high molecular weight polymer. Also, the polymer, which does ultimately form, has a lower molecular weight, which would lower adhesives strength [8,9]. 

While alkyl cyanoacrylate-based adhesives are used globally in a large variety of domestic and commercial settings, their physical and toxicological properties must be considered. Alkyl cyanoacrylate polymerization is a very exothermic reaction, so care must be taken to prevent the contamination of large quantities with any materials, which might initiate a very rapid, runaway reaction. Also, alkyl cyanoacrylate monomers and the polymers which they form, will burn, and users should avoid their use near sparks or open flames. 

As demonstrated earlier, the addition of other electron deficient monomers to copolymerize with the cyanoacrylate monomer has not proven to be an effective means of modifying the physical properties of cyanoacrylate-based adhesives. The most effective adhesive improvements have come through the incorporation of various additives, which modify the adhesive physical properties but do not copolymerize with the monomers. These product development efforts have been quite successful in improving the properties of alkyl cyanoacrylate-based adhesives to the point where they can now be used in a huge variety of applications. 

One of the latest developments in the field of closure is the availability of dermal liquid adhesives that can be used to close incisions. These are cyanoacrylate-based adhesives that are FDA approved and, although largely recommended for external use, they are bioabsorbable and, therefore, present the potential for use in conjunction with a knot for internal application. A study at North Carolina State University examined the efficacy on knot characteristics of coupling such adhesive with a number of surgeon s knots in a number of suture materials that differed in construction, size, and absorbability. ... 

Durability is one of the most important aspects of the performance of a structural adhesive. The durability of an adhesive joint is the sum total of its responses to environmental effects such as heat, moisture, other chemicals, radiation, and mechanical stresses. Cyanoacrylate-based adhesives have a reputation for poor durability, especially when bonding metals... 

In the last ten years, a number of improvements in cyanoacrylate adhesive technology have been published. Some of these modifications have been translated into new products. For instance, a series of adhesives is being sold with improved performance in the following areas contaminated surface bonding, hard-to-bond plastics, operating temperatures, moisture durability, impact strength, and chlorosis. A toughened cyanoacrylate based on a methyl acrylate-ethylene copolymer has been marked recently. An allyl cyanoacrylate-based adhesive with improved heat durability has also been introduced. A survey of recently patented modifications and improvements for cyanoacrylate adhesives is outlined in Table XIX. 

Polystyrene Although polystyrene is usually bonded by solvent cementing, it can be bonded with vinyl acetate/vinyl chloride solution adhesives, acrylics, polyurethanes, unsaturated polyesters, epoxies, urea-formaldehyde, rubber-base adhesives, polyamide (Versamid-base), polymethylmethacrylate, and cyanoacrylates. The adhesives should be medium-to-heavy viscosity and room-temperature and contact-pressure curing. An excellent source is a Monsanto Company technical information bulletin which recommends particular commercial adhesives for bonding polystyrene to a number of different surfaces. Adhesives are recommended in the fast-, medium-, and slow-setting ranges (10). 

Polysulfone A number of adhesives have been found useful for joining polysufone to itself or to other materials. These include 3M Company s EC 880 solvent-base adhesive, EC 2216 room-temperaturecuring epoxy two-part paste, Bloomingdale Division, American Cyana-mid Company BR-92 modified epoxy with DICY curing agent, or curing agent "Z" (both spreadable pastes), vinyl-phenolics, epoxy-nylons, epoxies, polyimide, rubber-based adhesives, styrene polyesters, resorcinol-formaldehyde, polyurethanes, and cyanoacrylates. The EC 880, EC 2216, and the two BR-92 adhesives are recommended by the polysulfone manufacturer. Union Carbide (16) (17). 

Cyanoacrylates are not appropriate for the bonding of the steel parts of an automobile, because of the environments that the car will be exposed to. Those environments include such things as rain, variations in temperatnre, exposure to solvents (such as gasoline, oil, and windshield washer solntion), ozone, acid rain, salt spray, and ultraviolet light from the Sun. (A more appropriate adhesive for car parts would be an epoxy-based adhesive.) Another example of a special adhesive would be the one used to attach a new rearview mirror in an antomobile. Because the cured adhesive in this case will be exposed to wide variations in temperature and to an extremely large amonnt of nltraviolet fight from the Snn for prolonged periods of time, an adhesive formnlated specifically for these conditions should be used. 

The rationale for developing the synthetic absorbable cyanoacrylate-based systems was consistent with certain minimum capabilities noted by Spotnitz for an ideal tissue adhesive. Accordingly, the ideal tissue adhesive should be ... 

Unique Properties of Absorbable Tissue Adhesives and Evolution of the Cyanoacrylate-Based Systems... 

Based on the design criteria noted above, the evolution of the absorbable cyanoacrylate-based system commenced with methoxypropyl cyanoacrylate (MFC) and was followed by formulation of MFC with polyether oxalate or polyester carbonate. Figure 5.1 outlines a polymerization scheme and designation of the final polymer. Both V-100 and V-150 tissue adhesives contain the same components but in different proportions. 

Fabric Peel Test Samples were cut from a plain weave cotton fabric (306 g/m ). Samples measuring 2.5 x 8 cm were cut, submerged in phosphate buffer (pH = 7.2), and allowed to air dry for 25 min. MFC measuring 350 (J-L (used as a model for cyanoacrylate-based tissue adhesives) was spread over a 2.5 X 6 cm area of one fabric sample, and a mating sample was placed on top. A 1200-g weight was set on top of the specimen for 1 min. The specimen was then allowed to cure for 1 h. The unglued portion was gripped into an MTS MiniBionix (Model 858) and the force required to separate the films at a displacement rate of 5.0 cm/min was measured. The maximum load after the initial peak was used to calculate the peel force of the adhesive joint. ... 

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