The functional requirements of bonded joints are extremely extensive in practical applications, often involving many key characteristics such as mechanical strength, heat resistance, oil resistance, waterproof performance, and electrical conductivity. In addition, it must fully meet the strict requirements of withstanding various environmental stresses. Correspondingly, the selected adhesives naturally need to possess matching functional characteristics. Only in this way can it be ensured that the bonded joints can play a stable role under different working conditions. Next, based on various typical functional requirements, the relevant adhesive varieties will be introduced in detail.

1. Mechanical strength          This type of adhesive must demonstrate excellent mechanical strength levels, specifically covering key indicators such as tensile strength, shear strength, and peel strength. Epoxy resin adhesives can be regarded as the "main force" among commonly used adhesives. However, it has certain shortcomings in terms of peel strength and its performance is not very satisfactory. If epoxy-butadiene acrylonitrile adhesive or phenolic-butadiene acrylonitrile adhesive is selected instead, satisfactory bonding results can often be achieved. Taking the repair of worn machine tool guideways as an example, this scenario urgently requires an adhesive with excellent wear resistance, and AR - 5 wear-resistant adhesive can play a significant role. Its hardness can be as high as 11.8HB, and this wear-resistant adhesive is skillfully mixed by epoxy resin and carefully selected inorganic fillers. Looking at the adhesives used for pasting plastic carpets and beverage bottle labels, they have relatively high requirements for shear strength, while the peel strength needs to be controlled at a relatively low level.

2.Heat resistance          Under normal circumstances, the upper limit of the long-term stable use temperature of most polymer adhesives is usually below 200°C. However, in some special application scenarios of specific materials, extremely harsh high-temperature requirements are imposed on the adhesives, that is, the long-term use temperature must exceed the 200°C threshold. For example, the adhesives used in the manufacturing process of microelectronic components need to accurately complete the bonding operation with a substrate as high as 400°C in a pure atmosphere carefully created by inert gas; the structural adhesives used in the structural assembly of supersonic aircraft must ensure that they can work continuously and stably for tens of thousands of hours without performance degradation at a high temperature of 230°C; the adhesives equipped on missile equipment are even more remarkable, requiring that they can still maintain mechanical properties steadily for at least 1 minute in an extremely high-temperature environment where the temperature rises instantaneously to 540°C. Obviously, these adhesives all belong to special-purpose categories customized for specific applications and are far beyond the reach of ordinary adhesives.