For cyanoacrylate adhesives

Primers for cyanoacrylate adhesives, chlorinated polyolefin primers... 

Method. An accurate weight of approximately 2.0 to 3.0 g of each polyurethane listed in Table 6.24 is placed in a clean platinum dish with 0.15 g of PTSA. The samples are ashed using a program of ramping/holding stages similar to methods described for cyanoacrylate adhesives to a maximum temperature of 650 °C. The resulting ashes are contacted with 10.0 ml of 0.1 M HC1 and the suspensions transferred to a Teflon beaker. To each add 2.0 ml of cone. HF and heat to -150 °C on a hot plate to dissolve the SiC>2. The clear solutions are made up to mark in a plastic volumetric flask with deionised water. 

Figure 1 General formula for cyanoacrylate adhesives. Copyright 2003 by Taylor Francis Group, LLC...

Anaerobic adhesives. Test nnethods for anaerobic adhesives nnay be obtained fronn the Ministry of Defence under DTD 5628 or from HMSO. Cyanoacryiate adhesives. Test methods for cyanoacrylate adhesives may be obtained from the Ministry of Defence under TS 468 and TS10168. 

Obviously a great deal of research effort has been directed toward developing stabilizers for cyanoacrylate adhesives. Two major types have evolved the volatile acid gases and the nonvolatile acids. These are used in varying concentrations, depending upon the type of stabilizer. Table III is a summary of the types of stabilizers used and typical concentrations. The end use of the adhesive also dictates the type and level of inhibitor used a fast-curing industrial ethyl cyanoacrylate adhesive will tolerate much... 

Over-stabilization is a temptation, in order to ensure long shelf lives for cyanoacrylate adhesive. This practice should be avoided because it leads to sluggish cure rates and inferior bond strengths. The use of strong protic acids can lead to hydrolysis of the cyanoacrylate ester group, producing alcohol which will destabilize the adhesive as its concentration increases. Because of the hydrolytic susceptibility of cyanoacrylate monomers, the water content of these adhesives should be kept as low as possible. Over-stabilization with strong acids should also be avoided in order to minimize hydrolysis. 

Several other examples of copolymeric thickeners can be found in the literature. For instance, copolymers of 20-80% methyl methacrylate and 80-20% acrylonitrile have been disclosed as thickeners for a dental cyanoacrylate adhesive. Recently, adhesives containing a plasticizer and a vinyl chloride-vinyl acetate copolymer were patented as additives for cyanoacrylate adhesives. The copolymers contained 10-20% vinyl acetate and less than 2% maleic acid. These polymers were not claimed as thickeners... 

Table XIX. A Survey of Patented Improvements For Cyanoacrylate Adhesives...

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. 

One-Component Polymerization Adhesives. Cyanoacrylate Adhesives. Methyl, ethyl, butyl, and methoxyethyl esters of cyanoacrylic acid are used for cyanoacrylate adhesives [44] soluble polymers and plasticizers are incorporated to regulate viscosity and for elastification. Cyanoacrylate adhesives rapidly polymerize by an ionic reaction mechanism initiated simply by weak bases to form high molecular mass, but largely uncross-linked polymers. In most cases, atmospheric moisture or the film of moisture on the substrate is sufficient to initiate polymerization, because the adhesives are applied in very thin layers. However, this sensitivity to atmospheric moisture means that the adhesives must be stored in tightly sealed form, usually in polyethylene bottles. Cyanoacrylates are used for bonding small items of nearly all substrates. In case of polyethylene or polypropylene special primers are available. Setting is complete with rubbers in seconds, with aluminum in less than one minute. 

Inhibitors of both anionic and free radical polymerization are essential to maintain a usable shelf life for cyanoacrylate adhesives. Coupled with advances in manufacturing processes to... 

The primer changes the surface condition of the plastic, creating bond sites for the cyanoacrylate adhesive. The effect of a polyolefin primer when used with a cyanoacrylate on polypropylene should not be underestimated. Bond strengths are often 25 to 40 times higher than those achieved when using the same adhesive without primer (Figure 6.4). Note that these polyolefin primers are only suitable for cyanoacrylate adhesives and are not compatible with other technology adhesives. 

---