Aliphatic amines such as diethylenetriamine (DETA) and hexamethylenediamine (HDA) react directly with the epoxy resin at room temperature, have a large exotherm, are explosive, and can be cured. Although they have high compressive strength, they are very brittle. Large, the use value is not high. The polyamide curing agent 650 has a slower reaction rate and can be toughened due to the dilution of the amine group and the spatial position of other organic groups in the molecule, but the polycondensation phenomenon occurs when a large amount of the rubber is dispensed. Dilution with a solvent can reduce the reaction rate, improve the heat transfer effect, lower the viscosity, and improve the operability. If an inert diluent such as a hydrocarbon, trichloroethylene or tetrachloroethylene is used, the compressive strength after curing is lowered, but the toughness is improved, and the compression set at the time of failure can be up to 20%, and it can be used in some cases. Incorporating a silicone coupling agent such as KH550, KH560, etc. into the diluent can increase the compressive strength, but the toughness is greatly reduced, and the compression shape at the time of failure becomes 7%.
Dilution with a solvent such as acetone improves heat transfer, reduces reaction rate, reduces system viscosity, and improves operability. In order to avoid the epoxy resin curing exotherm and accelerate the reaction to cause the explosion, a better method is to previously react the amine with a ketone (such as acetone) to form a ketimine, and then cool and then react with the epoxy resin. This not only facilitates the reaction speed and the control of the exothermic heat of the system, is less prone to explosion, reduces the initial viscosity, improves the workability and permeability to the substrate, increases the adhesion, and also improves the toughness of the adhesive after curing.
The advantages of adding a catalyst to a ketone imine to form a ketone imine and then catalyzing the curing of the epoxy resin are as follows: 1) reducing the curing reaction rate, reducing the reaction exotherm and preventing the explosion; 2) reducing the viscosity of the system and increasing the penetration. Sex, improve adhesion; 3) increase the compressive strength of the cured product and the yield strain is basically unchanged. Ketones are used as epoxy resin curing agents in a wide range of dosages to facilitate use to prevent formulation errors.
Bolt surface treatment There are two methods for the surface treatment of bolts, namely oxidation and galvanizing passivation. Regardless of whether the electroplating is acidic or alkaline, the workpiece acts as a cathode, which generates hydrogen gas on its surface. Especially when electroplating zinc-plated parts with a hardness of 329 HV or higher, hydrogen embrittlement failure is inevitable. In order to prevent the occurrence of hydrogen embrittlement failure phenomenon, this paper uses mechanical galvanizing to strengthen the surface strength and overall process performance of the bolt. Mechanical galvanizing is a special process that uses mechanical energy to deposit a layer of metallic zinc on the surface of a bolt substrate by the action of chemical additives. Put the bolts, glass beads and water in a special drum, add several kinds of chemical additives and zinc powder according to a certain process, transfer the energy by rotating the drum and glass beads, and make the zinc powder adhere firmly to the surface of the bolt to form a A layer of dense metallic zinc.
The bolts after degreasing and descaling are placed in a mechanical galvanizing drum together with water and medium to adjust the water temperature, and an acidic surface conditioner is added to the rotating drum. The surface conditioner removes scale from the surface of the bolt. The copper solution is then added to create a layer of impact copper on the bolt as the basis for the high adhesion of the coating, while forming the same metal surface on the bolt base material, subjecting to subsequent mechanical galvanizing, and then adding suitable mechanical galvanizing reagents. Adding a small amount of zinc powder creates an impact on the workpiece. The required amount of zinc powder and galvanizing medium are weighed according to the surface area of ​​the bolt and the thickness of the coating, and continuously added to the drum. Once the mechanical galvanizing process is complete, the bolts should be washed, the final water polished, bright and reinforced. After the mechanical galvanized bolts are separated from the glass beads, washed and dried, the galvanized bolts are delivered.
Heating Strip,Bright Strip,Nickel Alloy
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