Hardener additives

The higher the content of melamine, the higher is the stability of the hardened resin against the influence of humidity and water (hydrolysis resistance) [17, 45,46]. Resins containing melamine can be characterized by the molar ratio F (NH2)i or by the triple molar ratio F U M. The mass portion of melamine in the resin can be described as being based on the liquid resin or based on the total mass of urea and melamine in the resin (Table 6). MUF-resin hardener addition usually is distinctly higher than in UF-resins. 

Foam hardness is an important property of flexible foams because foam producers typically segregate grades of foam on the basis of the combination of foam hardness and density [163]. Foam formulations that can increase foam hardness without increasing density, or without the addition of hardening additives... 

Expanding cement (shrinkage-compensated cement) do not shrink upon hardening. Addition of 10 to 15% of calcium sulfate or aluminate even effects an expansion ( managed gypsum bursting ). 

Taking this circumstance into account some above topics will be analyzed lower in more details. Namely, these are limiting hardening created as a result of obtaining ultra-fine grains, some topics of deformation hardening additionally, considered will be some aspects of development of new generation of titanium-based materials (systems Ti-B-X and Ti-Si-X, where X is Al, Zr, etc.). 

Conventional plasticizers may be used in formulated products. Phthlate esters are the preferred plasticizers. They exhibit little tendency to migrate and have good compatibility with both resins and hardeners. Addition rates are typically 5 to 20%. Chlorinated plasticizers may be used to reduce flammability, especially in conjunction with antimony trioxide. The effect of plasticizer additions is generally to degrade most physical properties, although at low additions the effect is usually small. The effect of plasticizer additions on various important properties is as follows ... 

One of the most interesting tasks is to clarify if there is a real cocondensation within MUF resins or if two independent networks are formed, which only penetrate each other. The application of MUF resins is very similar to the UF resins, with the dilference that the level of hardener addition is usually much higher. 

Another example is shown by the thiol-ene system in which two different reactants A and B photochemically react to form larger molecules with concomitant reduction in solubility. Thus, in the presence of sensitizers/initiators, the multiple functional mercaptan (IV) will react with the multiple unsaturated oligomer (V) to form hardened addition products useful in letterpress platemalong (Figure 7). 

Hardening type Resin type Resin addition % on sand weight Catalyst/ hardener type Catalyst/ hardener addition % on resin weight Additive type Additive Addition % on sand weight... 

Temperature control The sand temperature must be maintained in a narrow range, with regular checks and adjustment of the amount of hardener addition. Positioning the sand heater just before the mixer allows close temperature control Mixer maintenance and cleaning... 

Sand temperature Determines the speed of hardening and the amount/type of hardener required A process control instrument can be used to adjust hardener additions to compensate for changes in sand temperature... 

Resin Hardener Additive Hardening temperature Adhesive strength (MPa) ... 

Uses Silicone chemical antistructuring (crepe hardening) additive for filled silicone... 

The layman s term for the time/lemperature related molecular cross-linking process - known more correctly as polymerisation - which occurs when a thermoset resin changes from the typically viscous liquid to the solid state. This cure process is normally also promoted following chemical activation by a catalyst - or often called, hardener -addition. Other chemical accelerators may be added by the resin manufacturer, or alternatively added to the resin immediately prior to the catalyst addition. Cure can also be activated in other ways, such as by the influence of ultra-violet radiation. No by-products are formed during the formation of these long molecular cross-linked chain links. 

Electroless nickel, which will provide good oxidation protection, with extra wear resistance if hardened. Additional improvements can be obtained by adding a further solid-lubricant coating of molybdenum disulfide (M0S2), ideally in an epoxy binder... 

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