1, liquid - operating time
The operating time (also the working time or period of use) is part of the curing time. After mixing, the resin/curing agent mixture is still liquid and can work and fit the application. In order to ensure reliable bonding, all construction and positioning work should be done during the curing operation time.
2, gel - enter curing
The mixture begins to enter the solidified phase (also known as the ripening stage), at which point it begins to gel or "mutate". At this time, the epoxy does not work for a long time and will lose its viscosity. No interference can be made at this stage. It will turn into a hard rubber-like soft gel that you can press with your thumb.
Since the mixture is only partially cured at this point, the newly used epoxy resin can still be chemically linked to it, so the untreated surface can still be bonded or reacted. In any case, the ability to approach the cured mixture is decreasing
3, solid - final curing
The epoxy mixture is solidified to a solid stage where it can be sanded and shaped. At this point you can't hold it with your thumb, at which point the epoxy resin has about 90% of the final reaction strength, so you can remove the retaining clip and leave it at room temperature to keep several angels from solidifying.
At this time, the newly used epoxy resin cannot be chemically linked with it, so the epoxy surface must be properly pretreated, such as sanding, to obtain good bonding mechanical strength.
Second, polyisocyanate
The main uses of related curing agents such as hybrid polyisocyanate curing agents are paints, foams, paints, and the like. The blocked water-dispersible polyisocyanate curing agent can also be used with a melamine assimilator to reduce the cost with a melamine curing agent, and the closed water dispersible polyisocyanate curing agent can improve the performance. Polyisocyanate is used in two-component polyurethane coatings. Two-component polyurethane coatings have become the mainstream technology in many applications, such as automotive refinish, large-scale vehicle paint, industrial paint, wood paint, plastic paint, and the like. With the concern of the society for environmental protection, high-performance curing agents that can reduce the emission of organic volatiles, such as water-dispersible curing agents and low-viscosity curing agents, will be the focus of future development. Hybrid polyisocyanate curing agents are optimistic in their future development based on their wide range of uses.
The development direction of curing agent is multi-functional, high-performance, flame-retardant, toughened, latent, energy-saving and environmentally friendly. In particular, more attention should be paid to energy conservation and environmental protection.
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