Commonly used inorganic adhesives are formulated with inorganic chemicals containing copper oxide and aluminum phosphate as the main components. It is characterized by good heat resistance and can withstand high temperatures of 900°C. This is not what ordinary organic adhesives can achieve. Its compressive strength is 90.0 mPa. The tensile strength is 14.5 MPa and the shear strength is 58.9 MPa. All are high. The disadvantage is that it is brittle and it is not resistant to impact, so it is not suitable for simple plane bonding, but suitable for socket or slot connection. The torsional shear strength of the socket connection is 50-60 MPa, and the axial shear strength is 90-100 MPa. Completely cured inorganic adhesives are insoluble in water and have good oil resistance. However, poor acid resistance and alkali resistance. If the adhesive pieces into 20% aqueous sodium hydroxide solution. Heating to boiling, the adhesive layer can be removed. After rinsing off the parts of the adhesive layer, it can be re-glued.
1. Bonding process
(1) Surface cleaning of adhesives
The steel parts are washed with caustic soda to wash off the oil; the aluminum parts can be heated to 90°C for 30 minutes with a mixture of 25 parts of sodium carbonate, 10 parts of soap and 100 parts of water. They can also be washed with gasoline or alcohol, and can be reused conditionally. The organic solvent such as acetone, trichloroethylene, etc. is scrubbed and then the rust layer can be removed with an emery cloth or a hand wheel.
(2) Select the connector of Taiwan
Inorganic adhesive should be grooved or socket joints as far as possible. If you must use flat glued and subject to greater load or impact. Should also use screw joints or rivet riveting and other auxiliary reinforcement measures.
(3) Selection of glue gap
Socketing gap between 0.2 ~ 0.4mm higher bonding strength. When the gap exceeds 0.4 mm, the strength rapidly decreases. If the surface is relatively smooth, or the glued joint will be subjected to impact load, the clearance should be selected smaller.
(4) Requirements for Adhesive Surfaces
Adhesive surface should be free of oil. No rust. In addition, the surface should be rough. To improve the bonding strength. For this purpose, the adhesive surface can be processed into tiny pits or hair threads.
(5) Coating
5. Apply evenly glue on the adhesive surface and apply some pressure when bonding. Or screw the adapter slowly in. To squeeze out excess glue. If it is a blind hole socket. Vents or small slots should be made in advance. Easy to remove air and filling glue.
(6) Curing
The glued parts can be cured after being placed at room temperature for 24 h. When conditional. The adhesive can be placed at room temperature for 3 ~ 4 h, so that the chemical reaction is more fully warmed to 60 ~ 80 °C curing 3 ~ 5 h. This measure helps the elimination of moisture in the adhesive layer and improves the bonding strength.
2. Inorganic adhesive repair example
When the plane body bolt hole on the engine body slips, if the use of reamer tapping, with the method of increasing the bolt to repair. The bolt will lose interchangeability. Therefore, an additional part method can be used to repair, that is, an internal and external threaded sleeve is glued to ensure the interchangeability of the bolts and ensure a good use effect. The operating points are as follows:
(1) Expand the threaded hole on the body from M16 to M22.
(2) The car has a threaded sleeve with threads inside and outside. The size is inner hole M16, outer column M22.
(3) Clean the surface to be adhered with acetone.
(4) Spread the inorganic glue evenly on the surface to be glued. Screw the screw sleeve into the hole of M22 so that the upper cylinder surface is flush with the plane of the machine body.
(5) Curing with a mixed curing method, that is, left at room temperature for 2-3 h, then irradiated with an infrared lamp to 60-80°C. Insulation 3-5 h. Then you can use it.