Factors Affecting Cure

The optimum cure condition for cyanoacrylates is when the relative humidity (RH) is between 40% RH and 60% RH. Lower RH, i.e., 20% RH, will result in a slower cure, and high RH (80% RH) result in a faster cure. A dry environment (low RH) often occurs when the work area heating system is switched on in the autumn months, thus drying out the local air adjacent to the work station. 

High RH can also be detrimental as the cyanoacrylate can sometimes cure so fast that the adhesive cures before it has properly adhered to the surface and the resulting bond is poor. 

Cyanoacrylates are best suited to parts with small gaps ( 0.1 mm). Some grades will cure through gaps up to 0.5 mm or even 1 mm using activators, but as a good rule of thumb the thinner the bond line the stronger the joint and the faster the cure. 

If excessive adhesive is applied, there is insufficient surface moisture and the cyanoacrylate will be slow to cure and may bloom (see Section 10.12.1). The adhesive should be applied 

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Deluyker H.A., Van Oye, S.N. and Boucher, J.F. (2005). Factors affecting cure and somatic cell count after pirlimycin treatment of subclinical mastitis in lactating cows . Journal of Dairy Science, 88, 604-614... 

Stages of Curing and Factors Affecting Cure Prepolymer Curing or Chain Extension... 

Recently, the curing characteristics of anaerobic sealants and adhesives (Fig. 13) were reported by Lees (60) and Stamper (64). The present systems can be cured rapidly in most metallic substrates, yet possess shelflives in excess of one year. The factors affecting curing are the cure system, surface preparation, substrate, temperature, and bondline thickness. 

Thus, the analysis of the reactivity ratios of the primary and secondary amino groups indicates that for conventional curing agents this cannot be regarded as a serious factor affecting the network topology. 

Another factor affecting thermal stability of componnds based on fluorocarbon elastomers is the curing (cross-linking) system nsed. This snbject is discussed at some length in the section on compounding. 

Three factors affect the properties of a vulcanizate (1) the percentage of sulfur and accelerator used, (2) the temperature, and (3) the time of cure. Sulfur is usually from 1 to 3% with strong acceleration the time can be as short as three minutes at high temperature (150C). Vulcanization can also occur at room temperature with specific formulations (self-curing cements). 

In a fundamental study of the factors affecting the growth of the rubber domains in a CTBN-toughened DGEBA epoxy resin cured by piperidine (Manzione and GilUiam, 1981) the kinetics of phase separation were linked to the diffusivity, Uab, of the rabber (A) dissolved in the epoxy resin (B). The relevant dependence on the molar volume of the rubber (proportional to the radius of the rubber molecules when dissolved in the epoxy resin) at the viscosity for the temperature T of reaction is given by the Stokes-Einstein equation ... 

Matsushita, H., Y. Tsujino, D. Yoshida, A. Saito, T. Kidaki, K. Kato, and M. Noguchi New minor alkaloids in flue-cured tobacco leaf Nicotiana tabacum cv. BY-260-9) Agr. Biol. Chem. 43 (1979) 193-194. Matthews, J.E. An investigation of certain factors affecting the composition of cigarette smoke Thesis, Pennsylvania State College (1941) pp. 1-77. 

The thickness of the adhesive layer is of importance in most adhesive joints and shonld be measnred and controlled in Tests of adhesion. Adhesive layer thickness is often determined by a nnmber of factors, some intentional in the design process and some resnlting from a variety of items related to the adhesive properties and the processing steps. Factors affecting the final bond thickness inclnde adhesive viscosity (which may fall dramatically and then rise during elevated temperature cure), clamping pressure and... 

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