Binder hardening

Influence of Temperature on RubCon Binder Hardening and Ways to Reduce It... 

The consumption levels of Ihe various types of binders, hardeners, catalysts and additives are given in Table 3.39. 

To Romans we also owe the name hydraulic cement as they defined the binders hardening under water and thanks to the reaction with water [3]. Some blended materials, in order to better define their composition, was called pozzolanic cements. 

Uses Solubilizer humectant binder, hardener in personal care prods. dispersant for dyes and pigments inks textiles coatings coloring ceramics paper industry softener plasticizer in adhesives industry and prod, of cellulose film ceramics and metalworking lubricants aux. for copper and nickel electroplating baths electrolytic polishing of steel Properties Wh. fine powd. m.w. 1500 water-sol. bulk dens. 0.6 kg/l vise. 25-35 cs (99 C) m.p. 45 C flash pt. > 230 C pH 6.0-7.5 (1% aq.) nonionic 100% cone. 

Uses Solubilizer humectant binder, hardener in personal care prods. dispersant for dyes and pigments inks textiles coatings coloring ceramics paper industry softener plasticizer in adhesives industry and prod, of cellulose film lubricant, dispersant, mold release for rubbers cure activator in min.-filled compds. 

Used as hot-melt binders. Hardening mechanism by solidification... 

Hydrated lime is also used to stabilize the calcium sulfite—sulfate sludge derived from thickeners at SO2 scmbbing plants that use limestone—lime. Hydrated lime (2—3%) is added to react with the gypsum sludge and flyash or other added siHceous material. Under ambient conditions the lime and siHca serve as a binder by reacting as calcium siHcates so that the material hardens into a safe, nonleaching, stable, sanitary landfill or embankment fill. 

The binder system of a plastic encapsulant consists of an epoxy resin, a hardener or curing agent, and an accelerating catalyst system. The conversion of epoxies from the Hquid (thermoplastic) state to tough, hard, thermoset soHds is accompHshed by the addition of chemically active compounds known as curing agents. Flame retardants (qv), usually in the form of halogens, are added to the epoxy resin backbone because epoxy resins are inherently flammable. 

Whereas semigloss paints can use only one extender, dat paints, especially interior, can use combinations of three or more. Gloss paints typically do not use extenders, which decrease gloss. As a result, gloss paints lack the hardening effect of extenders and must rely on harder binders for adequate durabihty. Other types of extenders used in paints can have functional properties such as corrosion resistance, mildew resistance, and film-hardening effects. Thek functional properties result from thek reactive nature in the paint film. Zinc oxide is an example of a functional extender that contributes to these properties in a paint film. 

For binder preparation, dilute hydrochloric or acetic acids are preferred, because these faciUtate formation of stable silanol condensation products. When more complete condensation or gelation is preferred, a wider range of catalysts, including moderately basic ones, is employed. These materials, which are often called hardeners or accelerators, include aqueous ammonia, ammonium carbonate, triethanolamine, calcium hydroxide, magnesium oxide, dicyclohexylamine, alcohoHc ammonium acetate, and tributyltin oxide (11,12). 

The specification requirements for electrode binder pitch, eg, high C/H ratio, high coking value, and high P-resin content, effectively ruled out pitches from gasworks or low temperature tars. The cmde tar is distilled to a medium-soft pitch residue and then hardened by heating for several hours at 385—400°C. This treatment increases the toluene-insoluble content and produces only a slight increase in the quinoline-insoluble (Ql) material, the latter by the formation of mesophase. 

A variety of materials has been proposed to modify the properties of asphaltic binders to enhance the properties of the mix (112), including fillers and fibers to reinforce the asphalt—aggregate mixture (114), sulfur to strengthen or harden the binder (115,116), polymers (98,117—121), mbber (122), epoxy—resin composites (123), antistripping agents (124), metal complexes (125,126), and lime (127,128). AH of these additives serve to improve the properties of the binder and, ultimately, the properties of the asphalt—aggregate mix. 

Carbon dioxide is widely used in the hardening of sand cores and molds in foundries. Sand is mixed with a sodium siHcate binder to form the core or mold after which it is contacted with gaseous carbon dioxide. Carbon dioxide reacts with the sodium siHcate to produce sodium carbonate and bicarbonate, plus siHcic acid, resulting in hardening of the core or mold without baking. 

When formulating a system for optimum abrasion resistance, both the epoxy/resin hardener binder system and the filler blends used appear to have an influence. The simulation of abrasive service loads on industrial floor toppings in a laboratory is not simple, and numerous wear test machines have been devised. Correlation between different wear test machines is not always good, although most... 

Alkaline phenolic resin, ester hardened. The binder is a low viscosity, highly alkaline phenolic resole resin (1.2 to 1.7%). The hardener is a liquid organic ester (18 to 25%). Sand is mixed with hardener and resin, usually in a continuous mixer. The speed of setting is controlled by the type of ester used. Low sand temperature slows the cure rate, but special hardeners are available for cold and warm sand. In 24 h compression strength can reach 4000 kPa (600 psi). 

Ester-cured alkaline phenolic system. The resin is an alkaline phenolic resin (essentially the same as the self-hardening resins of this type). Sand is mixed with the resin and blown or manually packed into a core box. A vaporized ester, methyl formate, is passed through the sand, hardening the binder. The total resin and peroxide addition is 1.5%. Compression strengths of 5000 kPa (700 psi) are possible. 

Carbon dioxide-silica process. Sand is mixed with sodium silicate (3.0 to 3.5% of sand volume), and the mixture is blown or hand-rammed into a core box or around a pattern. Carbon dioxide gas is passed through the compacted sand to harden the binder. The bonding strength eliminates the need for drying or baking the mold and metal can be poured into the mold immediately. Over-gassing should be avoided because it makes the mixture friable. 

A hydraulic setting cement is incorporated as the binder additive. The green pellets are partially hardened in silos, where they remain for about 24-36 hr, and the hardening process is completed during storage in stockpiles. 

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