Cold setting

An ink is considered dry when a print does not stick or transfer to another surface pressed into contact with it. Drying is accompHshed by one or more of the following physical or chemical mechanisms absorption, evaporation, precipitation, oxidation, polymerization, cold setting, gelation, and radiation curing. 

Cold Setting. In this process, also called hot-melt, inks are appHed to a substrate in a molten state and upon cooling form a dry ink film. 

Attempts have been made to use cold-set adhesives in the cormgating operation, such as poly(vinyl acetate) and modified, precooked starch formulations, but these have not achieved any appreciable degree of commercial acceptance (20). The use of a polyethylene film appHed to the inside surface of the linerboard facing, which serves as a hot-melt cormgator adhesive, has achieved some commercial usage. However, its use is limited to the small, specialty product niche of fast-food hamburger cartons (see Olefin polymers, polyethylene). 

J. J. Bechei, G. R. Hoffman,. W. Swanson, and R. C. McKee, Development of Cold-Set Adhesive, Project 2696-11, Report One to the Eouidiiniei Kraft Board Institute from the Institute of Paper Science and Technology, Adanta, Ga., Nov. 1973. 

Urea resin adhesives, by the use of the proper hardener, may be set either by heat or at room temperature. For room temperature curing, the hardener may be ammonium chloride, together with basic materials like calcium phosphate to neutralize excess acid that might damage the wood. Cold set or room temperature set adhesives are those that set satisfactorily at 20 —30°C, whereas a hot set adhesive generally means one that is set above 99 °C. 

Those that cure well between these temperatures are often referred to as intermediate set. Cold set types naturally set much faster at intermediate temperatures. Cold pressing of plywood is usually done in a hydraulic press. The press may then be opened, the clamped assembly removed and allowed to stay under the pressure of the clamps for at least four hours to set the glue. 

The viscosity of most adhesives increases with time as they set by cross-linking, cooling from the melt or loss of solvent. The cross-linking of a phenolic-polyvinyl formal adhesive and of cold-setting epoxies was found by de Bruyne [41] to be represented adequately by an exponential relationship ... 

Laminated beams (glulam), parallam (or LSL) and fingerjoints a flat pressed multilayer wood beam, thiek wood planks constituting the layers, used for structural exterior applications and bonded with PRF (phenol-resorcinol-formaldehyde) cold-setting resins, or MUF cold-setting resins, or even with certain types of polurethanes (although the use of these latter ones is only established in one country and can show creep and temperature-induced creep problems). The indi-... 

Where resorcinol adhesives are not suitable, resins can be prepared from modified resorcinol [128], Characteristic of these types of resins arc those used for tyre cord adhesives, in which a pure resorcinol-formaldehyde resin is used, or alternatively, alkyl resorcinol or oil-soluble resins suitable for rubber compounding are obtained by prereaction of resorcinol with fatty acids in the presence of sulfuric acid at high temperature followed by reaction with formaldehyde. Worldwide more than 90% of resorcinol adhesives are used as cold-setting wood adhesives. The other most notable application is as tyre cord adhesives, which constitutes less than 5% of the total use. 

More recently, a modification of the system described by Kreibich has been used extensively in industry with good success. Part A of the adhesive is again a standard phenol-resorcinol-formaldehyde (PRF) cold-setting adhesive, with powder hardener added at its standard pH. Part B can be either the same PRF adhesive with no hardener and the pH adjusted to 12, or a 50 to 55% tannin extract solution at a pH of 12-13, provided that the tannin is of the condensed or flavonoid type, such as mimosa, quebracho, or pine bark extract, with no hardener [118,135-137], The results obtained with these two systems are good and the resin not only has all the advantages desired but also the use of vegetable tannins and the halving of the resorcinol content makes the system considerably cheaper [118,135-137]. 

There are, however, certain materials used as ingredients in the manufacture of plastics, which almost invariably give a corrosive product. Included in this category are wood, which is frequently used as a filler or as part of a composite drying oils, used in paints, adhesives, jointing compounds and linoleum and esters of volatile acids frequently retained in certain cold setting formulations, especially some paints. ... 

The metal electrode to be studied must be carefully prepared, attached to an electrical lead and mounted so that a known surface area of one face is presented to the solution. Several procedures are used such as mounting in a cold setting resin (Araldite) or inserting into a close-fitting holder of p.t.f.e. In the case of metal-solution systems that have a propensity for pitting care must be taken to avoid a crevice at the interface between metal specimen and the mounting material, and this can be achieved effectively by mounting the... 

Fig. 19.9 Methods of mounting specimens, (a) Wire soldered to metal specimen, wire being enclosed in glass tube (b) specimen completely encapsulated in cold-setting resin and resin ground down to expose one face (c) specimen clipped into machined p.t.f.e. holder (d) Stern-Makrides pressure gasket for cylindrical specimen (e) pressure gasket for sheet or foil ...

Kingery, W. D. (1950b). Fundamental study of phosphate bonding in refractories. II. Cold setting properties. Journal of the American Ceramic Society, 33, 242-7. 

As adhesives they are very widely used both as cold setting and thermo curing. They can bond together a large variety of surfaces including metals. Araldite resins of this type are used widely in aircraft construction. They are also used for bonding concrete in dams and joining teflon film to stainless steel. They are used to encapsulate delineate electrical parts to protect them from shock and moisture. Such parts are used in components of rockets and satellites. 

Figure 9. Diagrammatic illustration of the utilization of the meta-hydroxy-methylation of lignin for the production of cold set wood adhesives.

Bolder, S.G., Hendrickx, H., Sagis, L.M.C., van der Linden, E. (2006). Ca2+-induced cold-set gelation of whey protein isolate fibrils. Applied Rheology, 16, 258- 264. 

Figure 2.1 Scanning electron micrographs of Fe -induced cold-set gels of P-lactoglobulin filamentous gel (top) and particulate gel (bottom). The gel microstructure depends on the iron/protein ratio. At low iron/protein ratios, a homogeneous filamentous network is obtained, whereas at high iron/protein ratios an aggregated particle gel is produced. Reproduced from Chen et al (2006a) with permission.

Maltais, A., Remondetto, G.E., Gonzales, R., Subirade, M. (2005). Formation of soy protein isolate cold-set gels protein and salt effects. Journal of Food Science, 70, 67-73. 

Bryant, M.C., McClements, D.J. (1998). Molecular basis of protein functionality with special consideration of cold-set gels derived from heat-denatured whey. Trends in Food Science and Technology, 9, 143-151. 

Nitroguanidine is dissolved in acetic acid, diluted to approximately 10%, treated with zinc dust in the cold, set aside for thirteen to nineteen minutes and filtered 6% cupric sulphate solution is than added to the filtrate. The solution turns intensely blue and on boiling, becomes turbid, gives off gas and deposits a precipitate of metallic copper. If silver acetate is added instead of cupric sulphate a precipitate of metallic silver is deposited on boiling. 

Syntactic foams have been made from organosilicone polymers and glass, ceramic, or polymer microspheres 23,100). They are used mainly for heat insulation and ablation coating101). For the latter, the two components are sprayed together onto the exterior of rockets, and cold setting silicone glues are used to improve ablation102). Syntactic materials with carbon microspheres and silicones have also been proposed 39>. 

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