① The adhesive shall be in a liquid state when applied, regardless of its original condition. ② It shall be able to spread completely and fully wet the surface of the bonded material. ③ It must be able to transform from liquid to solid or gel by some means, forming a tough and stable adhesive layer. ④ After curing, it shall have sufficient strength to achieve reliable bonding, transfer stress, and resist failure. ⑤ It shall be resistant to temperatures above 0℃ and withstand testing for a certain period of time.