? I. Application of Epoxy Resin Adhesive
The modified epoxy resin adhesive and the preparation method thereof overcome the defects of high brittleness and poor temperature resistance of common epoxy adhesives. Its main technical feature is that polyurethane prepolymer modified epoxy resin (component A) and self-made curing agent (component B) are prepared into high temperature resistance and high temperature resistance according to the ratio of10:1~1:1(weight ratio). Among them, polyurethane prepolymer is hydroxyl-terminated polysiloxane and diisocyanate, which react in a certain proportion under certain conditions to prepare isocyanate-terminated polysiloxane polyurethane prepolymer, and then epoxy resin is modified with this polyurethane prepolymer.
The self-made curing agent consists of diamine, imidazole compounds, silane coupling agent, inorganic filler and catalyst. The modified epoxy resin adhesive can be cured at room temperature, and can be used for a long time at 200℃, or cured at -5℃, with a temperature resistance of 65438 050℃; The adhesive strength reaches15-30 MPa; The T-shaped peel strength reaches 35-65N/cm, and it has excellent oil resistance, water resistance, acid resistance, alkali resistance and organic solvent resistance, and can be used for bonding wet surfaces, oil surfaces, metals, plastics, ceramics, hard rubber, wood, etc.
Secondly, research on the selection of fillers.
The heat resistance of adhesive is not only related to the types, varieties and molecular structures of basic polymers, curing crosslinking agents and other components in the system, but also closely related to the heat-resistant fillers selected in the system. Proper introduction of heat-resistant filler in the formula will often obviously improve the heat-resistant performance of the system.
Commonly used heat-resistant fillers include surface-modified fumed silica, surface-treated zinc oxide, iron oxide and alumina. After surface treatment, the heat resistance of fillers can be obviously improved, such as silicone rubber system with (MeSi)2NH treated silica as filler. Even after 48 hours at 250℃, its tensile strength is 9.3Mpa, and its elongation is 335%, if the same kind of silica without surface treatment is used.
The same silicone rubber system as the filler. After thermal aging under the same conditions, the tensile strength and elongation are 6.6Mpa and 228% respectively. Visible. Heat-resistant filler can significantly improve the heat resistance of silicone rubber.
All kinds of carbon black, nano calcium carbonate, titanium dioxide, etc. It has the functions of strengthening, improving various physical properties, thickening, reducing cost and coloring. Fillers can reduce the shrinkage of products. Reduce internal stress. It is of great significance to improve the comprehensive performance. For example, quartz powder can improve the hardness of the adhesive layer and the fluidity of the potting adhesive; Silicon micropowder can improve the bonding strength, but the storage period will be shortened: adding a small amount of zinc chromate can improve the wet heat resistance and salt spray resistance; Adding 325 mesh glass flake has excellent corrosion resistance and water resistance; Adding calcium sulfate whisker has obvious toughening and strengthening effects, improving heat resistance and boiling water resistance. Flame retardant and antimony trioxide improve oxygen index and antioxidant 264, and prolong the service life of cured products.
The example recommended above is about the advantages, characteristics and applicable places of epoxy resin adhesive. It can be seen that the product has good cohesiveness, good functionality, low price and simple bonding process, and is widely used in processing and construction operations in industrial fields such as electronics, electricity, water conservancy and transportation. In addition, we can find that different epoxy adhesives can be classified, for example, according to the strength required by applicable conditions, and the applicable methods are not the same.
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