The principles for choosing adhesives in the repair of construction machinery

Adhesives have special functions and practical value and are widely used in the repair of construction machinery. There are over ten thousand types of adhesives suitable for different uses in the world. When choosing adhesives, the following four indicators should be considered.

(1) Medium resistance

Air, water, oil, acid, etc. are collectively referred to as substances. The vast majority of adhesives have the best resistance to air media, and the bonding strength of the bonded parts in the air is the highest. However, the adhesive force varies greatly in different types of gases or injection media. Even during the working process, the main substances at the contact Angle are air, water, oil and acid, etc. When using adhesives, those that are resistant to the medium of use should be selected.

(2) Bonding strength

The destructive force per 1cm² of the bonding surface at room temperature and in air medium is called the bonding strength, expressed in MPa. Bonding strength is further divided into tensile strength, shear strength, torsional shear strength and peel strength, which respectively refer to the failure strength of the bonded parts under different force directions. When choosing an adhesive, one should select a strength adhesive that is suitable for the position and force conditions of the mechanical parts.

(3) Temperature resistance performance

It refers to the temperature range that the fully cured adhesive layer can withstand. For example, a certain temperature resistance range of -60 ° C to 120 ° C means that this adhesive can be used within the range of -60 ° C to 120 ° C. Beyond this limit, the adhesive force will significantly decrease. The air-cooled engine in construction machinery can reach a body temperature of 130 ° C. The temperature of the hydraulic oil can reach 120 ° C. When choosing the adhesive, it must be within the temperature range that the adhesive can withstand.

(4) Curing time

The curing time can be divided into initial curing (or fixed) time and full curing time. It refers to the time required for the adhesive to transform from a gel-like state to a solid state at room temperature during bonding. Initial curing refers to the time required for the adhesive layer to withstand the bonded parts without falling off due to its own weight. Full curing refers to the time required for the adhesive layer to fully cure and achieve the highest tack strength and the best resistance to media. Adhesives can be classified into two types based on their initial setting time: instant adhesives (or fast-drying adhesives) and slow-drying adhesives. The initial setting time of instant adhesive is only a few seconds or tens of seconds. For slow-drying adhesives, if it is necessary to shorten the curing time, measures such as heat blowing or baking in an oven can be used to increase the temperature, but the heating temperature and time should be determined according to different types of adhesives. Choose between instant drying or slow-drying adhesive types, depending on the different conditions of the bonded parts and the work requirements. Generally speaking, the bonding strength and medium resistance of slow-drying adhesives are superior to those of instant adhesives.

The above points are the basic principles for choosing adhesives in the repair of construction machinery. Only by correctly choosing adhesives can the expected effect be achieved and the performance of the machinery be restored.