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An intermediate case involves a mixture of resin and additives that requires external stimulus (light, heat, radiation) to induce curing. The curing methodology depends on the resin and the application. Particular attention is paid to the shrinkage induced by the curing. Usually small values of shrinkage (2–3%) are desirable. [2]
Curing of epoxy resins is an exothermic reaction and in some cases produces sufficient heat to cause thermal degradation if not controlled. [28] Curing does induce residual stress in epoxy systems which have been studied. [29] The induced stresses may be alleviated with flexibilisers.
J-B Kwik is a faster-curing two-part epoxy with medium-temperature resistance up to 300 °F (149 °C). Although not as strong or heat-resistant as J-B Weld, it has the same adhesion and does not shrink when hardening.
[12] [13] From the 1990s onward, concern has been raised over the use of BADGE-based epoxy resins in the lining of some cans for foodstuffs, with the chemical being found to leach into foods. [ 12 ] [ 14 ] Bisphenol A Diglycidyl ether-based epoxy coatings are extensively used for coating the inside of cans which come into contact with food and ...
The curing process is by condensation and a typical figure for Redux Liquid 775/Powder 775 is 30 minutes at 293 °F (145 °C) under a pressure of 100 psi (690 kPa). This is not critical and variations in curing-time and/or temperature may be used to increase shear and creep strength at temperatures above 140 °F (60 °C).
As reaction proceeds, larger and larger molecules are formed and highly branched crosslinked structures develop, the rate of cure being influenced by the physical form and functionality of epoxy resins and curing agents [3] – elevated temperature postcuring induces secondary crosslinking of backbone hydroxyl functionality which condense to ...