Cyanoacrylate ethyl

Fig. 11. Effect of polyolefin primers on bond strength of ethyl cyanoacrylate to plastics. All assemblies tested in accordance with ASTM D 4501 (block shear method). ETFE = ethylene tetrafluoroethylene copolymer LDPE = low-density polyethylene PFA = polyper-fluoroalkoxycthylene PBT = polybutylene terephthalate, PMP = polymethylpentene PPS = polyphenylene sulfide PP = polypropylene PS = polystyrene PTFE = polytetrafluoroethylene PU = polyurethane. From ref. [73].

The initiation mechanism is well defined because of the recent isolation and spectroscopic characterization of the initial zwitterion from ethyl cyanoacrylate (ECA) and a phosphine [8,9]. Specifically, zwitterion 4 was prepared from the reaction of equimolar amounts of dimethylphenyl phosphine, 5, and ECA, 6,... 

Ethyl cyanoacrylate is the monomer which is most widely used in both consumer and industrial applications, because of its combination of fast cure speed and ease of manufacture. 

Crosslinking has been claimed to improve thermal resistance of the cyanoacrylate adhesive [18]. However, in other reports [6], little or no improvement in thermal resistance of the adhesive was demonstrated by the addition of a difunctional monomer. As seen in Fig. 2, the addition of varying amounts of crosslinker 7 provided no improvement in the tensile adhesive strength of ethyl cyanoacrylate on steel lapshears after thermal exposure at 121 °C for up to 48 h. 

More recently, the copolymerization of ethyl cyanoacrylate with other 1,1 disubstituted electron deficient monomers and the effect of the monomers on adhesive properties have been studied. Monomers, such as diethyl methylene-malonate (DEMM), 8, were prepared [6,7]. Their homopolymers and copolymers... 

The molecular weights of the polymers are much larger than would be predicted from the monomer/initiator ratio, as seen in Fig. 4. However, this effect is most evident for the polymerization of ethyl cyanoacrylate alone. 

The adhesive properties the other monomers were also evaluated, alone and as mixtures with ethyl cyanoacrylate. The addition of DEMM to ECA has an obvious negative effect on adhesion, as can be seen in Fig. 5. 

All of the eommereial alkyl eyanoaerylate monomers are low-viseosity liquids, and for some applications this can be an advantage. However, there are instances where a viseous liquid or a gel adhesive would be preferred, sueh 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. 

An example of this improvement in toughness can be demonstrated by the addition of Vamac B-124, an ethylene/methyl acrylate copolymer from DuPont, to ethyl cyanoacrylate [24-26]. Three model instant adhesive formulations, a control without any polymeric additive (A), a formulation with poly(methyl methacrylate) (PMMA) (B), and a formulation with Vamac B-124 (C), are shown in Table 4. The formulation with PMMA, a thermoplastic which is added to modify viscosity, was included to determine if the addition of any polymer, not only rubbers, could improve the toughness properties of an alkyl cyanoacrylate instant adhesive. To demonstrate an improvement in toughness, the three formulations were tested for impact strength, 180° peel strength, and lapshear adhesive strength on steel specimens, before and after thermal exposure at 121°C. 

The addition of Vamac B-124 to ethyl cyanoacrylate has a more pronounced effect on peel strength, both at ambient temperature and after thermal exposure. After 24 h at ambient temperature, the peel strength of the rubber-toughened formulation is almost 40% greater than the control formulation A without rubber. After heating the test specimens for 2 h at 121°C, the peel strength of formulation A, is almost non-existent, while that of C has increased significantly, as seen in Fig. 7. 

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. 

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]. 

Despite the universal use of sutures for wound closure, there is a need to utilize adhesives instead, because of their ease of use and the reduced risk of infection. Alkyl cyanoacrylate adhesives have been studied extensively for this use, and a significant amount of research has been performed to evaluate their interaction with living tissue [40,41 J. They have been approved for external use only, because of concerns with the fact that the polymers do not readily biodegrade and can cause inflammation around the area to which it was applied. However, these concerns are reduced for -butyl cyanoacrylate, as compared to the ethyl cyanoacrylate. There is even some evidence that their use as liquid sutures actually reduces the rate of infection around the healing wound or surgical incision [42J. 

Polymeric ethyl cyanoacrylate exhibits very low toxicity properties. In tests with laboratory rats, oral administration of 6400 mg/kg of the polymer failed to harm the test animals. Some skin irritation did occur in tests on guinea pigs, but skin sensitization or absorption through the skin was not observed [45]. 

Technical Data Sheet for Gel Set 44 Ethyl Cyanoacrylate, http //www.holdtite.com/english/technical/tech/ca44.htm... 

World Health Organization Concise International Chemical Assessment Document (CICAD) 36, Methyl Cyanoacrylate and Ethyl Cyanoacrylate. pp 1-19. International Programme on Chemical Safety (IPCS), Geneva, 2001... 

The group polymerized mechanically the dispersed methyl or ethyl cyanoacrylate in aqueous acidic medium in the presence of polysorbate-20 as a surfactant under vigorous mechanical stirring to polymerize alkyl cyanoacrylate. The polymerization follows an anionic mechanism since it is initiated in the presence of nucleophilic initiators like OH- in an acidic medium (pH 1.0-3.5). The same group coated PACA nanoparticles with various polysaccharides introducing modifications in the method (Couvreur et al. 1978 Vauthier et al. 2003 Betrholon-Rajot et al. 2005). 

The next three polymers in this series are aU ethyl acrylates, meaning that while the backbone (a) substituent is different in all three structures, the ester side-chain group (P) is the same for aU of them ( CH2CH3). Polymer 3 is poly(ethyl methacrylate) (PEMA), and 4 is poly(ethyl cyanoacrylate) (PECA), which may be recognizable as a primary component of the so-called superglues. Polymer 5 is poly(ethyl acrylate) (PEA), with H on the backbone a-position. Erom structure 3 to 4 to 5, the a-substituent becomes simpler in structure and this will be reflected in the observed TREPR spectra below in terms of the number of observed transitions, and in some cases the linewidths as well. 

A number of strategies for the photochemical initiation of anion or cation catalyzed polymerization have been explored. For example, visible photolysis of the Reineckate anion, [Cr(NH3)2(NCS)4], has long been known to release a thiocyanate ion. Photolysis of the Reineckate anion in the presence of ethyl cyanoacrylate initiates polymerization. The release of acac anions, and benzoylcyclopentadienyl... 

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