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J-B Weld epoxy is a two-part adhesive that can bond various surfaces and withstand high temperatures up to 500 °F (260 °C) constantly and 600 °F (316 °C) for short periods. It is water-resistant, petroleum/chemical-resistant, acid-resistant, and resists shock, vibration, and temperature fluctuations.
At this time, the part in question can be handled, but cannot handle large loads or stress. It typically takes up to 24 hours for a standard epoxy to cure to its final and complete strength. [2] [3] Temperature is an important factor in the time it takes for an adhesive to form the green strength. While this can vary from adhesive to adhesive ...
The second most important part of FBE coatings is the curing agent or hardener. Curing agents react either with the epoxy ring or with the hydroxyl groups, along the epoxy molecular chain. Various types of curing agents, used in FBE manufacture, include dicyandiamide, aromatic amines, aliphatic diamines and organic acid anhydrides. [6]
The variation of G' and G" in time can indicate the extent of the curing reaction. [7] As shown in Figure 4, after an "induction time", G' and G" start to increase, with an abrupt change in slope. At a certain point they cross each other; afterwards, the rates of G' and G" decrease, and the moduli tend to a plateau.
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.
The epoxy value is defined as the number of moles of epoxy group per 100g resin. So as an example using an epoxy resin with molar mass of 382 and that has 2 moles of epoxy groups per mole of resin, the EEW = 382/2 = 191, and the epoxy value is calculated as follows: 100/191 = 0.53 (i.e. the epoxy value of the resin is 0.53). [6]