In the development of the epoxy resin curing agent industry, functional curing agents have become a research and development hotspot. There must be many users who do not understand it. Here, epoxy resin curing agent manufacturers will tell you about the development trend of epoxy resin curing agents.
①Multifunctionality. (It has the functions of curing, toughening, flame retardant, promotion, etc.) The curing agent has become the ideal product that people pursue. Since the development of epoxy resins with brand-new structures and excellent performances has not made much progress, the functional additives that meet the requirements of resin modification have become the goals pursued by people, and more and more products with one dose are more and more.
②The epoxy resin curing agent has developed rapidly in the direction of rapid curing, low temperature curing and small water absorption.
③The curing agent for special functions has also been greatly developed, such as the elastic curing agent.
2 Development of epoxy resin curing agent industry-low toxicity and non-toxicity is the future development direction
① A characteristic of the development of modern curing agents is that people not only pay attention to the toxicity and environmental pollution of curing agents during production and use, but also pay attention to the environmental pollution of waste epoxy resin products.
②In developed countries, the primary polyene multi-glue and aromatic amines have all been replaced by non-toxic or low-toxic modified amines.
Three stages of epoxy resin curing
1 liquid-operating time
The operating time (also working time or service life) is part of the curing time. After mixing, the resin/curing agent mixture is still liquid and works and is suitable for use. In order to ensure reliable bonding, all construction and positioning work should be done within the curing operation time.
2 gel-enter curing
The mixture begins to enter the solidified phase (also known as the curing stage), at which point it begins to gel or "mutate". The epoxy at this time has no possibility of long-term work and will also lose its tack. At this stage, there must be no interference. It will become a soft gel like hard rubber, you can press it with your thumb. Because the mixture is only partially cured at this time, 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, these capabilities of the near-cured mixture are decreasing.
3 solid-final curing
The epoxy mixture reaches the stage of solidification and solidification, at which time it can be sanded and shaped. At this time, you can't press it with your thumb. At this time, the epoxy resin has about 90% of the final reaction strength, so you can remove the fixing clip and leave it at room temperature to maintain a few angels. It continues to cure. At this time, the newly used epoxy resin cannot be chemically linked with it, because the epoxy surface needs to be properly pretreated, such as sanding, to achieve good bonding mechanical strength.
Selection of curing agent
1 Consider the variety and performance of the curing agent
The type of curing agent has a great influence on the mechanical properties, heat resistance, water resistance and corrosion resistance of the cured product, such as aromatic polyamine, imidazole, acid anhydride and other curing agents. The heat resistance of cured epoxy resin is higher than that of fat Polyamine, low molecular polyamide curing agent; aromatic acid anhydride cured epoxy resin has better water resistance than aromatic diamine and aliphatic polyamine curing agent; triethylenetetramine curing agent has good alkali resistance, but acid resistance and Formaldehyde resistance is poor. The alicyclic polyamine (such as isophorone diamine) cured epoxy resin has excellent chemical resistance. The alkali resistance of the epoxy resin cured by the acid anhydride curing agent is better than the acid resistance. The appropriate curing agent should be selected according to different uses and performance requirements.
2Several curing agents are used in combination
Combined use of several curing agents can achieve a mutually reinforcing effect. For example, low molecular polyamide curing agent combined with a small amount of m-phenylenediamine curing agent can not only cure at room temperature, but also increase the toughness of the cured product while appropriately increasing heat resistance. Sex. Trimellitic anhydride (TMA) is used in combination with methyltetrahydrophthalic anhydride. The viscosity of the eutectic mixture is low (25℃, 200～250mPa·s). It is easy to mix with epoxy resin and improve the processability.
3 Pay attention to the environmental protection of the curing agent
The selected curing agent should be harmless to the human body. Ethylenediamine cannot be used alone as a curing agent. Use modified amine curing agents as much as possible. In addition, the choice of curing agent depends on the effect of the curing agent, whether it can improve the ground hardness and other performance can be improved, and also consider dealing with the problems that occur on the ground.